Estimation and reduction of bias in self-controlled case series with non-rare event dependent outcomes and heterogeneous populations

The self-controlled case series (SCCS) is a commonly adopted study design in the assessment of vaccine and drug safety. Recurrent event data collected from SCCS studies are typically analyzed using the conditional Poisson model which assumes event times are independent within-cases. This assumption is violated in the presence of event dependence, where the occurrence of an event influences the probability and timing of subsequent events. When event dependence is suspected in an SCCS study, the standard recommendation is to include only the first event from each case in the analysis. However, first event analysis can still yield biased estimates of the exposure relative incidence if the outcome event is not rare. We first demonstrate that the bias in first event analysis can be even higher than previously assumed when subpopulations with different baseline incidence rates are present and describe an improved method for estimating this bias. Subsequently, we propose a novel partitioned analysis method and demonstrate how it can reduce this bias. We provide a recommendation to guide the number of partitions to use with the partitioned analysis, illustrate this recommendation with an example SCCS study of the association between beta-blockers and acute myocardial infarction, and compare the partitioned analysis against other SCCS analysis methods by simulation.

Estimation of trajectory of protective efficacy in infectious disease prevention trials using recurrent event times

In studies of infectious disease prevention, the level of protective efficacy of medicinal products such as vaccines and prophylactic drugs tends to vary over time. Many products require administration of multiple doses at scheduled times, as opposed to one-off or continual intervention. Accurate information on the trajectory of the level of protective efficacy over time facilitates informed clinical recommendations and implementation strategies, for example, with respect to the timing of administration of the doses. Based on concepts from pharmacokinetic and pharmacodynamic modeling, we propose a non-linear function for modeling the trajectory after each dose. The cumulative effect of multiple doses of the products is captured by an additive series of the function. The model has the advantages of parsimony and interpretability, while remaining flexible in capturing features of the trajectories. We incorporate this series into the Andersen-Gill model for analysis of recurrent event time data and compare it with alternative parametric and non-parametric functions. We use data on clinical malaria disease episodes from a trial of four doses of an anti-malarial drug combination for chemoprevention to illustrate, and evaluate the performance of the methods using simulation. The proposed method out-performed the alternatives in the analysis of real data in terms of Akaike and Bayesian Information Criterion. It also accurately captured the features of the protective efficacy trajectory such as the area under curve in simulations. The proposed method has strong potential to enhance the evaluation of disease prevention measures and improve their implementation strategies.

PRECIOUS demonstrated satisfactory measurement properties for assessing the quality of care for children with serious illnesses

OBJECTIVES

To determine the measurement properties of PaRental Experience with care for Children with serIOUS illnesses (PRECIOUS), a parent-reported measure of Quality of Care for seriously ill children across care settings and illness trajectories.

STUDY DESIGN AND SETTING

Parents self-administered baseline and 2-week follow-up surveys online. Exploratory Factor Analysis was used to determine PRECIOUS's factor structure and select items. Internal consistency was evaluated with Cronbach's α, test-retest reliability with intraclass correlation coefficients, and convergent validity with Spearman's correlations between PRECIOUS scales and subscales of Measure of Processes of Care and Quality of Children's Palliative Care Instrument.

RESULTS

Of 152 parents [108 (71%) mothers, 44 (29%) fathers] who completed the baseline survey, 123 (81%) completed follow-up. Exploratory Factor Analysis grouped PRECIOUS into five scales: collaborative and goal-concordant care (12 items), caregiver support and respectful care (15 items), access to financial and medical resources (five items), reducing caregiving stressors (nine items), and hospitalization-specific processes (four items). Root Mean Square Error of Approximation was 0.040 and Comparative Fit Index was 0.980. Cronbach's α ranged from 0.85 to 0.96. Intraclass correlation coefficients ranged from 0.72 to 0.86. Significant correlations with Measure of Processes of Care and Quality of Children's Palliative Care Instrument confirmed convergent validity. The original 56-item tool was reduced to 45 items.

CONCLUSION

PRECIOUS demonstrates satisfactory measurement properties for assessing Quality of Care for seriously ill children.

Can an Integrated Palliative and Oncology Co-rounding Model Reduce Aggressive Care at the End of Life? Secondary Analysis of an Open-label Stepped-wedge Cluster-randomized Trial

BACKGROUND

Clinical trial evidence on the effect of palliative care models in reducing aggressive end-of-life care is inconclusive. We previously reported on an integrated inpatient palliative care and medical oncology co-rounding model that significantly reduced hospital bed-days and postulate additional effect on reducing care aggressiveness.

OBJECTIVES

To compare the effect of a co-rounding model vs usual care in reducing receipt of aggressive treatment at end-of-life.

METHODS

Secondary analysis of an open-label stepped-wedge cluster-randomized trial comparing two integrated palliative care models within the inpatient oncology setting. The co-rounding model involved pooling specialist palliative care and oncology into one team with daily review of admission issues, while usual care constituted discretionary specialist palliative care referrals by the oncology team. We compared odds of receiving aggressive care at end-of-life: acute healthcare utilization in last 30 days of life, death in hospital, and cancer treatment in last 14 days of life between patients in two trial arms.

RESULTS

2145 patients were included in the analysis, and 1803 patients died by 4th April 2021. Median overall survival was 4.90 (4.07 - 5.72) months in co-rounding and 3.75 (3.22 - 4.21) months in usual care, with no difference in survival (P = .12). We found no significant differences between both models with respect to receipt of aggressive care at end-of-life. (Odds Ratio .67 - 1.27; all P > .05).

CONCLUSION

The co-rounding model within an inpatient setting did not reduce aggressiveness of care at end-of-life. This could be due in part to the overall focus on resolving episodic admission issues.

ENABLE-SG (Educate, Nurture, Advise, Before Life Ends for Singapore) as a proactive palliative care model: protocol for a hybrid type 1 effectiveness-implementation randomized wait-list controlled trial

BACKGROUND

Specialist palliative care is often provided late in the patient's disease trajectory in response to uncontrolled symptoms. Shifting from this reactionary illness-stress paradigm to a proactive health-wellness approach, the ENABLE (Educate, Nurture, Advise, Before Life Ends) telehealth model aims to enhance the coping, stress and symptom management, self-care, and advance care planning skills of patients with advanced cancers and their caregivers. The ENABLE model has been culturally adapted to Singapore (ENABLE-SG) and pilot-tested. A hybrid type 1 effectiveness-implementation design will be used to evaluate the effectiveness of ENABLE-SG while collecting real-world implementation data.

METHODS

This single-centre, assessor-blind, wait-list (immediately vs. 6 months) randomized controlled trial will recruit 300 adult patients within 60 days of an advanced cancer diagnosis and their family caregivers from the National Cancer Centre of Singapore. ENABLE-SG comprises structured psychoeducational sessions with a telehealth coach, covering essential topics of early palliative care. Participants will be assessed at baseline and every 3 months until patient's death, 12 months (caregivers), or end of study (patients). The primary outcome is patient quality of life 6 months after baseline. Secondary patient-reported outcomes include mood, coping, palliative care concerns, and health status. Secondary caregiver-reported outcomes include caregiver quality of life, mood, coping, and care satisfaction. Mixed-effects regression modelling for repeated measurements will be used. To assess the effectiveness of ENABLE-SG versus usual care, patient and caregiver outcomes at 6 months will be compared. To compare earlier versus delayed ENABLE-SG, patient and caregiver outcomes at 12 months will be compared. Within the hybrid type 1 effectiveness-implementation design, implementation outcomes will be evaluated in both the early and delayed groups. Acceptability, adoption, appropriateness, and feasibility will be assessed using a feedback survey and semi-structured interviews with a purposive sample of patients, caregivers, and healthcare providers. Transcribed interviews will be analysed thematically. Other implementation outcomes of penetration, fidelity, and cost will be assessed using records of study-related processes and summarized using descriptive statistics. A cost-effectiveness analysis will also be conducted.

DISCUSSION

This study will assess both effectiveness and implementation of ENABLE-SG. Insights into implementation processes can facilitate model expansion and upscaling.

TRIAL REGISTRATION

Registered prospectively on ClinicalTrials.gov, NCT06044441. Registered on 21/09/2023.

Cluster randomized trial designs for modeling time-varying intervention effects

Stepped-wedge cluster randomized trials (SW-CRTs) are typically analyzed assuming a constant intervention effect. In practice, the intervention effect may vary as a function of exposure time, leading to biased results. The estimation of time-on-intervention (TOI) effects specifies separate discrete intervention effects for each elapsed period of exposure time since the intervention was first introduced. It has been demonstrated to produce results with minimum bias and nominal coverage probabilities in the analysis of SW-CRTs. Due to the design's staggered crossover, TOI effect variances are heteroskedastic in a SW-CRT. Accordingly, we hypothesize that alternative CRT designs will be more efficient at modeling certain TOI effects. We derive and compare the variance estimators of TOI effects between a SW-CRT, parallel CRT (P-CRT), parallel CRT with baseline (PB-CRT), and novel parallel CRT with baseline and an all-exposed period (PBAE-CRT). We also prove that the time-averaged TOI effect variance and point estimators are identical to that of the constant intervention effect in both P-CRTs and PB-CRTs. We then use data collected from a hospital disinvestment study to simulate and compare the differences in TOI effect estimates between the different CRT designs. Our results reveal that the SW-CRT has the most efficient estimator for the early TOI effect, whereas the PB-CRT typically has the most efficient estimator for the long-term and time-averaged TOI effects. Overall, the PB-CRT with TOI effects can be a more appropriate choice of CRT design for modeling intervention effects that vary by exposure time.

Associations of predominant night-eating with plasma glycemic status and continuous glucose monitoring measures among pregnant women

BACKGROUND & AIMS

To examine whether predominant night-eating, defined as more than 50% of total daily energy intake consumed between 1900 and 0659 h, is associated with glycemic outcomes in pregnancy.

METHODS

This was a prospective cohort study of 277 healthy pregnant women with complete 4-day dietary intake records at 18-24 weeks gestation, recruited from KK Women's and Children's Hospital, Singapore. Primary outcomes were fasting, 1-h, and 2-h plasma glucose after a 75-g oral glucose tolerance test at 24-28 weeks gestation. Secondary outcomes were gestational diabetes mellitus (GDM), fasting insulin, homeostasis model assessment of insulin resistance (HOMA2-IR), β-cell function (HOMA2-%B), and continuous glucose monitoring (CGM) measures. Glucose variables in continuous form were loge-transformed before analyses.

RESULTS

Predominant night-eating (11.6%) was associated with higher fasting glucose (geometric mean ratio (95% confidence interval) 1.05 (1.01, 1.08)) and 1-h glucose (1.11 (1.01, 1.21)), but not with 2-h glucose or GDM risk. Predominant night-eating women had lower fasting insulin (0.77 (0.63, 0.95)), lower HOMA2-IR (0.78 (0.64, 0.97)), and lower HOMA2-%B (0.77 (0.67, 0.89)) than their predominant day-eating counterparts. For CGM measures, predominant night-eating was associated with higher mean glucose (1.07 (1.00, 1.15)), higher glucose management indicator (1.05 (1.00, 1.10)), and higher overall glucose levels throughout 24 h (1.10 (1.02, 1.19)). All these associations were adjusted for socio-demographic, lifestyle factors, and diet composition.

CONCLUSION

Predominant night-eating was mainly associated with less desirable glycemic outcomes during pregnancy. Future studies should explore dietary interventions aimed at reducing consumption of relatively more calories at night than day during pregnancy.

Statistical analysis plan for the LAKANA trial: a cluster-randomized, placebo-controlled, double-blinded, parallel group, three-arm clinical trial testing the effects of mass drug administration of azithromycin on mortality and other outcomes among 1-11-month-old infants in Mali

BACKGROUND

The Large-scale Assessment of the Key health-promoting Activities of two New mass drug administration regimens with Azithromycin (LAKANA) trial in Mali aims to evaluate the efficacy and safety of azithromycin (AZI) mass drug administration (MDA) to 1-11-month-old infants as well as the impact of the intervention on antimicrobial resistance (AMR) and mechanisms of action of azithromycin. To improve the transparency and quality of this clinical trial, we prepared this statistical analysis plan (SAP).

METHODS/DESIGN

LAKANA is a cluster randomized trial that aims to address the mortality and health impacts of biannual and quarterly AZI MDA. AZI is given to 1-11-month-old infants in a high-mortality setting where a seasonal malaria chemoprevention (SMC) program is in place. The participating villages are randomly assigned to placebo (control), two-dose AZI (biannual azithromycin-MDA), and four-dose AZI (quarterly azithromycin-MDA) in a 3:4:2 ratio. The primary outcome of the study is mortality among the intention-to-treat population of 1-11-month-old infants. We will evaluate relative risk reduction between the study arms using a mixed-effects Poisson model with random intercepts for villages, using log link function with person-years as an offset variable. We will model outcomes related to secondary objectives of the study using generalized linear models with considerations on clustering.

CONCLUSION

The SAP written prior to data collection completion will help avoid reporting bias and data-driven analysis for the primary and secondary aims of the trial. If there are deviations from the analysis methods described here, they will be described and justified in the publications of the trial results.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT04424511 . Registered on 11 June 2020.

Protocol update and baseline characteristics for the TRIal to slow the Progression of Diabetes (TRIPOD) randomized controlled trial

BACKGROUND

Type 2 diabetes (T2D), a major risk factor for cardiovascular disease and other adverse health conditions, is on the rise in Singapore. TRIPOD is a randomized controlled trial aimed to determine whether complementing usual care with an evidence-based diabetes management package (DMP) -comprising access to an evidence-based app, health coaching, pedometer, glucometer and weighing scale, with or without a financial rewards scheme (M-POWER rewards), can improve mean HbA1c levels at months 6 and 12.

METHODS

The protocol was published in Trials, accessible via https://trialsjournal.biomedcentral.com/articles/10.1186/s13063-019-3749-x 1. This manuscript updates the protocol with changes to the study design due to challenges with recruitment and presents baseline characteristics. Key updates include changing the arm allocation ratio from 1:1:1 (Arm 1-Usual Care: Arm 2-DMP: Arm 3-DMP+M-POWER rewards) to 10:1:10, the sample size from 339 to 269, the intervention period from two to one year, and the primary hypothesis to focus solely on differences between Usual Care and DMP+M-POWER rewards. Recruitment for the study began on 19 October 2019 and ended on 4 June 2022.

RESULTS

The average age of participants was 55.0 (SD9.7) years old and 64.2% were male. The majority of participants (76.8%) were Chinese, 4.9% Malay and 18.3% Indian and of other ethnicities. 67.0% had a monthly household income of SGD$4000 or more. The mean baseline HbA1c was 8.10% (SD 0.95) and the mean body mass index was 26.8 kg/m2 (SD 5.3).

DISCUSSION

The final participant completed month 12 follow-up data collection on 8 June 2023. All pre-planned analyses will be conducted and final results reported.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03800680 . Registered on 11 January 2019.

Novel 3-arm wait-list controlled trial designs together with mixed-effects analysis improve precision of treatment effect estimators

Clinical trialists have long been searching for approaches to increase statistical power without increasing sample size. Conventional wait-list controlled (WLC) trials are limited to two trial arms and two or three repeated measurements per person. These features limit statistical power. Furthermore, their analysis is usually based on analysis of covariance or mixed effects modelling, with a focus on estimating treatment effect at one time-period after initiation of therapy. We propose two 3-arm WLC trial designs together with a mixed-effects analysis framework. The designs require three or four repeated measurements per person. The analytic framework defines up to three treatment effect estimands, representing the effects at one to three time-periods after initiation of therapy. The precision (inverse of variance) of the treatment effect estimators in the new and conventional trial designs are analytically derived and evaluated in simulations. The results are interpreted in the context of a cognitive training trial in older people. The proposed designs and analysis methods increase the precision level of treatment effect estimators as compared to conventional designs and analyses. Given a target level of statistical power, the proposed methods require a smaller number of participants per trial than the conventional methods, without necessarily increasing the number of measurements per trial. Furthermore, the proposed analytic framework sheds light on the treatment effects at different times after initiation of therapy, which is not usually considered in conventional WLC trial analysis. In situations that a WLC trial is appropriate, the 3-arm designs are useful alternatives to existing 2-arm designs.

Palliative care pain control: inpatient consultation versus corounding models compared

BACKGROUND

Compared with the current inpatient consultation model, a novel corounding model of care whereby palliative specialists round with oncology teams, increases healthcare collaboration and may improve quality of care for inpatients. Whether this translates to better pain control for patients is unexplored.

OBJECTIVE

To determine whether the corounding model provides better pain control compared with the consultation model for cancer inpatients.

METHODS

Cancer patients with moderate or severe pain severity during the admission were included in this observational study. Pain severity was determined using electronic records. Improvement to mild or no pain by day 3 of identification of moderate or severe pain was defined as good pain control and proportion of admissions achieving this was compared between models.

RESULTS

A total of 142 and 128 admissions admitted under the consult and corounding model, respectively, had moderate or severe pain. The proportion of patients that achieved good pain control was 77.3% (99/128) and 71.8% (102/142) in the corounding and consult model, respectively. The difference in proportion of admissions achieving good pain control was significantly higher in the corounding model after adjusting for differences in baseline characteristics (unadjusted OR, 1.34; 95% CI, 0.77 to 2.33; adjusted OR, 2.25; 95% CI, 1.19 to 4.26).

DISCUSSION

The odds of achieving good pain control was significantly better in the corounding model. However, the mechanism behind this is unexplored. This study can serve as precedence for future studies evaluating the corounding model of care.

Measurement Properties of the 15-Item Singapore Caregiver Quality of Life Scale (SCQOLS-15) in Family Caregivers of Patients with Heart Diseases

PURPOSE

To evaluate the measurement properties of the 15-item Singapore Caregiver Quality of Life Scale (SCQOLS-15) in family caregivers of patients with heart diseases.

METHODS

The SCQOLS-15 survey was self-administered by family caregivers of patients with chronic heart diseases, at baseline and 1 week later. The criterion validity of SCQOLS-15 and its domain scores was assessed by calculating the Spearman correlation coefficient (ρ) with the Brief Assessment Scale for Caregivers (BASC), Caregiver Reaction Assessment (CRA), and their sub-scores. Known-group validity was assessed using the New York Heart Association (NYHA) functional class. Test-retest reliability was evaluated using the intraclass correlation coefficient (ICC).

RESULTS

Of the 327 caregivers included, 65% were adult children and 28% were spouses. The distribution of NYHA classes of the patients was I: 27%, II: 40%, III: 24%, and IV: 9%. There was a positive correlation between the SCQOLS-15 and BASC total scores (ρ = 0.7). SCQOLS-15 domain scores were also correlated with BASC and CRA sub-scores as per a priori hypotheses, with absolute values of ρ ranging from 0.4 to 0.6. The mean values of SCQOLS-15 total and all domain scores were lower among caregivers of patients with NYHA class III/IV compared to those of class I/II patients (each P < 0.05). Among 146 caregivers who completed the follow-up and self-rated a stable quality-of-life, ICCs for test-retest reliability of SCQOLS-15 total and all domain scores were ≥ 0.8.

CONCLUSION

The SCQOLS-15 is a valid and reliable instrument for measuring the quality of life in caregivers of heart disease patients.

The relationship between hope, medical expenditure and survival among advanced cancer patients

Introduction

Among those with advanced illness, higher levels of hope may offer physiological benefits. Yet, greater levels of hope may also encourage aggressive treatments. Therefore, higher levels of hope may lead to greater healthcare utilization, higher expenditure, and longer survival. We test these hypotheses among patients with advanced cancer.

Methods

A secondary data analysis from a cross-sectional survey of 195 advanced cancer patients with high mortality risk linked to subsequent healthcare utilization (outpatient, day surgeries, non-emergency admissions), health expenditures, and death records. The survey collected data on hope, measured generally by the Herth Hope Index (HHI) and more narrowly by two questions on illness-related hope. Generalized linear regression and Cox models were used to test our hypotheses.

Results

142 (78%) survey participants died during the period of analysis, with close to half (46%) doing so within a year of the survey. Contrary to expectation, HHI scores did not have a significant association with healthcare utilization, expenditure or survival. Yet, illness-related hope, defined as those who expected to live at least 2 years, as opposed to the likely prognosis of 1 year or less as determined by the primary treating oncologist, had 6.6 more planned hospital encounters (95% CI 0.90 to 12.30) in the 12-months following the survey and 41% lower mortality risk (hazard ratio: 0.59, 95% CI 0.36 to 0.99) compared to those who were less optimistic. Secondary analysis among decedents showed that patients who believed that the primary intent of their treatment is curative, had higher total expenditure (S$30,712; 95% CI S$3,143 to S$58,282) in the last 12 months of life than those who did not have this belief.

Conclusion

We find no evidence of a relationship between a general measure of hope and healthcare utilization, expenditure, or survival among advanced cancer patients. However, greater illness-related hope is positively associated with these outcomes.

Distribution and association of interpregnancy weight change with subsequent pregnancy outcomes in Asian women

The extent of interpregnancy weight change and its association with subsequent pregnancy outcomes among Asians remain unclear. We examined changes in maternal body mass index (BMI) between the first two deliveries and outcomes in the second delivery. Medical records of women with their first two consecutive deliveries between 2015 and 2020 at KK Women's and Children's Hospital, Singapore were retrieved. Gestational-age-adjusted BMI was determined by standardising to 12 weeks gestation and interpregnancy BMI change was calculated as the difference between both pregnancies. Pregnancy outcomes were analysed using modified Poisson regression models. Of 6264 included women with a median interpregnancy interval of 1.44 years, 40.7% had a stable BMI change within ± 1 kg/m², 10.3% lost > 1 kg/m², 34.3% gained 1-3 kg/m² and 14.8% gained ≥ 3 kg/m². Compared to women with stable BMI change, those with > 1 kg/m² loss had higher risk of low birthweight (adjusted risk ratio [RR] 1.36; 95% confidence interval 1.02-1.80), while those with 1-3 kg/m² gain had higher risks of large-for-gestational-age birth (1.16; 1.03-1.31), gestational diabetes (1.25; 1.06-1.49) and emergency Caesarean delivery (1.16; 1.03-1.31); these risks were higher in those with ≥ 3 kg/m² gain. Our study strengthens the case for interpregnancy weight management to improve subsequent pregnancy outcomes.

Modelling non-linear patterns of time-varying intervention effects on recurrent events in infectious disease prevention studies

Protective efficacy of vaccines and pharmaceutical products for prevention of infectious diseases usually vary over time. Information on the trajectory of the level of protection is valuable. We consider a parsimonious, non-linear and non-monotonic function for modelling time-varying intervention effects and compare it with several alternatives. The cumulative effects of multiple doses of intervention over time can be captured by an additive series of the function. We apply it to the Andersen-Gill model for analysis of recurrent time-to-event data. We re-analyze data from a trial of intermittent preventive treatment for malaria to illustrate and evaluate the method by simulation.

The Impact of Antenatal Azithromycin and Monthly Sulfadoxine-Pyrimethamine on Maternal Malaria during Pregnancy and Fetal Growth: A Randomized Controlled Trial

Maternal malaria and infections during pregnancy are risk factors for fetal growth restriction. We assessed the impact of preventive treatment in pregnancy on maternal malaria and fetal growth. Between 2003 and 2006, we enrolled 1,320 pregnant Malawian women, 14-26 gestation weeks, in a randomized trial and treated them with two doses of sulfadoxine-pyrimethamine (SP, control) at enrollment and between 28-34 gestation weeks; with monthly SP from enrollment until 37 gestation weeks; or with monthly SP and azithromycin twice, at enrollment and between 28 and 34 gestation weeks (AZI-SP). Participants were seen at 4-week intervals until 36 completed gestation weeks and weekly thereafter. At each visit, we collected dried blood spots for real-time polymerase chain reaction diagnosing of malaria parasitemia and, in a random subgroup of 341 women, we measured fetal biparietal diameter and femur length with ultrasound. For the monthly SP versus the control group, the odds ratios (OR) (95% CI) of malaria parasitemia during the second, third, and both trimesters combined were 0.79 (0.46-1.37), 0.58 (0.37-0.92), and 0.64 (0.42-0.98), respectively. The corresponding ORs for the AZI-SP versus control group were 0.47 (0.26-0.84), 0.51 (0.32-0.81), and 0.50 (0.32-0.76), respectively. Differences between the AZI-SP and the monthly SP groups were not statistically significant. The interventions did not affect fetal biparietal diameter and femur length growth velocity. The results suggest that preventive maternal treatment with monthly SP reduced malaria parasitemia during pregnancy in Malawi and that the addition of azithromycin did not provide much additional antimalarial effect.

Modifiable Risk Factor Score and Fecundability in a Preconception Cohort in Singapore

IMPORTANCE

Although multiple modifiable risk factors have been identified for reduced fecundability (defined as lower probability of conception within a menstrual cycle), no scoring system has been established to systematically evaluate fecundability among females who are attempting to conceive.

OBJECTIVE

To examine the association of a risk score based on 6 modifiable factors with fecundability, and to estimate the percentage reduction in incidence of nonconception if all study participants achieved a minimal risk score level.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study obtained data from the S-PRESTO (Singapore Preconception Study of Long-Term Maternal and Child Outcomes) prospective cohort study. Females of reproductive age who were trying to conceive were enrolled from February 2015 to October 2017 and followed for 1 year, ending in November 2018. Data were analyzed from March to May 2022.

EXPOSURES

A reduced fecundability risk score was derived by giving participants 1 point for each of the following factors: unhealthy body mass index, unhealthy diet, smoking, alcohol intake, folic acid supplement nonuser, and older maternal age. Total scores ranged from 0 to 6 and were classified into 5 levels: level 1 (score of 0 or 1), level 2 (score of 2), level 3 (score of 3), level 4 (score of 4), and level 5 (score of 5 or 6).

MAIN OUTCOMES AND MEASURES

Fecundability, measured by time to conception in cycles, was analyzed using discrete-time proportional hazards models with confounder adjustment.

RESULTS

A total of 937 females (mean [SD] age, 30.8 [3.8] years) were included, among whom 401 (42.8%) spontaneously conceived within 1 year of attempting conception; the median (IQR) number of cycles before conception was 4 (2-7). Compared with participants with a level 1 risk score, those with level 2, 3, 4, and 5 risk scores had reductions in fecundability of 31% (adjusted fecundability ratio [FR], 0.69; 95% CI, 0.54-0.88), 41% (FR, 0.59; 95% CI, 0.45-0.78), 54% (FR, 0.46; 95% CI, 0.31-0.69) and 77% (FR, 0.23; 95% CI, 0.07-0.73), respectively. Assessment of the population attributable fraction showed that all participants achieving a minimal (level 1) risk level would be associated with a reduction of 34% (95% CI, 30%-39%) in nonconception within a year.

CONCLUSIONS AND RELEVANCE

Results of this study revealed the co-occurrence of multiple modifiable risk factors for lowered fecundability and a substantially higher conception rate among participants with no or minimal risk factors. The risk assessment scoring system proposed is a simple and potentially useful public health tool for mitigating risks and guiding those who are trying to conceive.

Testing the effects of mass drug administration of azithromycin on mortality and other outcomes among 1-11-month-old infants in Mali (LAKANA): study protocol for a cluster-randomized, placebo-controlled, double-blinded, parallel-group, three-arm clinical trial

BACKGROUND

Mass drug administration (MDA) of azithromycin (AZI) has been shown to reduce under-5 mortality in some but not all sub-Saharan African settings. A large-scale cluster-randomized trial conducted in Malawi, Niger, and Tanzania suggested that the effect differs by country, may be stronger in infants, and may be concentrated within the first 3 months after treatment. Another study found no effect when azithromycin was given concomitantly with seasonal malaria chemoprevention (SMC). Given the observed heterogeneity and possible effect modification by other co-interventions, further trials are needed to determine the efficacy in additional settings and to determine the most effective treatment regimen.

METHODS

LAKANA stands for Large-scale Assessment of the Key health-promoting Activities of two New mass drug administration regimens with Azithromycin. The LAKANA trial is designed to address the mortality and health impacts of 4 or 2 annual rounds of azithromycin MDA delivered to 1-11-month-old (29-364 days) infants, in a high-mortality and malaria holoendemic Malian setting where there is a national SMC program. Participating villages (clusters) are randomly allocated in a ratio of 3:2:4 to three groups: placebo (control):4-dose AZI:2-dose AZI. The primary outcome measured is mortality. Antimicrobial resistance (AMR) will be monitored closely before, during, and after the intervention and both among those receiving and those not receiving MDA with the study drugs. Other outcomes, from a subset of villages, comprise efficacy outcomes related to morbidity, growth and nutritional status, outcomes related to the mechanism of azithromycin activity through measures of malaria parasitemia and inflammation, safety outcomes (AMR, adverse and serious adverse events), and outcomes related to the implementation of the intervention documenting feasibility, acceptability, and economic aspects. The enrolment commenced in October 2020 and is planned to be completed by the end of 2022. The expected date of study completion is December 2024.

DISCUSSION

If LAKANA provides evidence in support of a positive mortality benefit resulting from azithromycin MDA, it will significantly contribute to the options for successfully promoting child survival in Mali, and elsewhere in sub-Saharan Africa.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04424511. Registered on 11 June 2020.

Dietary Supplement Intake and Fecundability in a Singapore Preconception Cohort Study

Subfertility is a global problem affecting millions worldwide, with declining total fertility rates. Preconception dietary supplementation may improve fecundability, but the magnitude of impact remains unclear. This prospective cohort study aimed to examine the association of preconception micronutrient supplements with fecundability, measured by time to pregnancy (TTP). The study was conducted at KK Women's and Children's Hospital, Singapore, between February 2015 and October 2017, on 908 women aged 18-45 years old, who were trying to conceive and were enrolled in the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO). Baseline sociodemographic characteristics and supplement intake were collected through face-to-face interviews. The fecundability ratio (FR) was estimated using discrete-time proportional hazard modelling. Adjusting for potentially confounding variables, folic acid (FA) (FR 1.26, 95% confidence interval 1.03-1.56) and iodine (1.28, 1.00-1.65) supplement users had higher fecundability compared to non-users. Conversely, evening primrose oil supplement users had lower fecundability (0.56, 0.31-0.99) than non-users. In this study, preconception FA and iodine supplementation were associated with shortened TTP, while evening primrose oil use was associated with longer TTP. Nonetheless, the association between supplement use and the magnitude of fecundability changes will need to be further confirmed with well-designed randomised controlled trials.

Nocturnal Lifestyle Behaviour and Sleep Quality During Pregnancy

Objectives

Little is known about the extent to which lifestyle practices at night influence sleep quality in pregnant women who are susceptible to sleep disturbances. This study aimed to examine the association between nocturnal lifestyle behaviour and sleep quality of women during pregnancy.

Methods

This observational cross-sectional study recruited pregnant women between 18 and 24 weeks of gestation from KK Women's and Children's Hospital, Singapore. Nocturnal lifestyle behaviour was assessed by frequency of night eating after 8 pm, moderate-to-vigorous physical activity performance after 7 pm, screen viewing > 1 hour before bedtime and artificial light exposure with ≥ 10 lux between 2–4 am. Sleep quality was measured using the Pittsburgh Sleep Quality Index with global score > 5 indicative of poor sleep quality. Modified Poisson regression model tested the association between nocturnal lifestyle behaviour and sleep quality.

Results

Of 299 women, 117 (39.1%) exhibited poor sleep quality. In the covariate-adjusted analysis, an increased risk of poor sleep quality was observed in women with night eating (risk ratio 1.54; 95% confidence interval 1.15, 2.06) and light exposure at night (1.74; 1.34, 2.25). No associations were observed for night-time physical activity (0.84; 0.60, 1.17) and screen viewing before bedtime (1.10; 0.76, 1.60) with sleep quality.

Conclusions

More than one-third of pregnant women experienced poor sleep quality. Night eating and artificial light exposure at night were associated with poor sleep quality during pregnancy. Thus, reducing night eating and decreasing levels of exposure to light at night represent potential targets for healthy sleep interventions in pregnancy, in a bid to augment efforts to promote sleep quality among pregnant women.

Funding Sources

This study is supported by the Singapore Ministry of Health's National Medical Research Council under its Open Fund-Young Individual Research Grant.

A prospective cohort study assessing aggressive interventions at the end-of-life among patients with solid metastatic cancer

Background

Many patients with a solid metastatic cancer are treated aggressively during their last month of life. Using data from a large prospective cohort study of patients with an advanced cancer, we aimed to assess the number and predictors of aggressive interventions during last month of life among patients with solid metastatic cancer and its association with bereaved caregivers’ outcomes.

Methods

We used data of 345 deceased patients from a prospective cohort study of 600 patients. We surveyed patients every 3 months until death for their physical, psychological and functional health, end-of-life care preference and palliative care use. We surveyed their bereaved caregivers 8 weeks after patients’ death regarding their preparedness about patient’s death, regret about patient’s end-of-life care and mood over the last week. Patient data was merged with medical records to assess aggressive interventions received including hospital death and use of anti-cancer treatment, more than 14 days in hospital, more than one hospital admission, more than one emergency room visit and at least one intensive care unit admission, all within the last month of life.

Results

69% of patients received at least one aggressive intervention during last month of life. Patients hospitalized during the last 2–12 months of life, male patients, Buddhist or Taoist, and with breast or respiratory cancer received more aggressive interventions in last month of life. Patients with worse functional health prior to their last month of life received fewer aggressive interventions in last month of life. Bereaved caregivers of patients receiving more aggressive interventions reported feeling less prepared for patients’ death.

Conclusion

Findings suggest that intervening early in the sub-group of patients with history of hospitalization prior to their last month may reduce number of aggressive interventions during last month of life and ultimately positively influence caregivers’ preparedness for death during the bereavement phase.

Trial registration

NCT02850640.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12904-022-00970-z.

Metabolic health status and fecundability in a Singapore preconception cohort study

BACKGROUND

Obesity compromises metabolic health and female fertility, yet not all obese women are similar in metabolic status. The extent to which fecundability is influenced by the metabolic health status of women who are overweight or obese before conception is unknown.

OBJECTIVE

This study aimed to: (1) determine the metabolic health status, and (2) examine the association between metabolic health status and fecundability of overweight and obese women trying to conceive in the Singapore PREconception Study of long-Term maternal and child Outcomes cohort study.

STUDY DESIGN

We conducted a prospective preconception cohort study of Asian women (Chinese, Malay, and Indian) aged 18 to 45 years trying to conceive who were treated from 2015 to 2017 in KK Women's and Children's Hospital in Singapore (n=834). We defined women to have metabolically unhealthy status if they: (1) met 3 or more modified Joint Interim Statement metabolic syndrome criteria; or (2) had homeostasis model assessment-insulin resistance index ≥2.5. Body mass index was categorized as normal (18.5-22.9 kg/m2), overweight (23-27.4 kg/m2), or obese (≥27.5 kg/m2) on the basis of cutoff points for Asian populations. Fecundability was measured by time to pregnancy in menstrual cycles within a year of enrolment. Discrete-time proportional hazards models were used to estimate fecundability odds ratios, with adjustment for confounders and accounting for left truncation and right censoring.

RESULTS

Of 232 overweight women, 28 (12.1%) and 25 (10.8%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Of 175 obese women, 54 (30.9%) and 93 (53.1%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Compared with metabolically healthy normal-weight women, lower fecundability was observed in metabolically unhealthy overweight women on the basis of metabolic syndrome criteria (fecundability odds ratios, 0.38 [95% confidence interval, 0.15-0.92]) and homeostasis model assessment-insulin resistance (fecundability odds ratios, 0.68 [95% confidence interval, 0.33-1.39]), with metabolic syndrome criteria showing a stronger association. Metabolically unhealthy obese women showed lower fecundability than the healthy normal-weight reference group by both metabolic syndrome (fecundability odds ratios, 0.35; 95% confidence interval, 0.17-0.72) and homeostasis model assessment-insulin resistance criteria (fecundability odds ratios, 0.43; 95% confidence interval, 0.26-0.71). Reduced fecundability was not observed in overweight or obese women who showed healthy metabolic profiles by either definition.

CONCLUSION

Overweight or obesity was not synonymous with having metabolic syndrome or insulin resistance. In our preconception cohort, metabolically unhealthy overweight and obese women showed reduced fecundability, unlike their counterparts who were metabolically healthy. These findings suggest that metabolic health status, rather than simply being overweight and obese per se, plays an important role in fecundability.

Investigating 5-Level EQ-5D (EQ-5D-5L) Values Based on Preferences of Patients With Heart Disease

OBJECTIVES

Several studies have shown that patients with heart disease value hypothetical health states differently from the general population. We aimed to investigate the health preferences of patients with heart disease and develop a value set for the 5-level EQ-5D (EQ-5D-5L) based on these patient preferences.

METHODS

Patients with confirmed heart disease were recruited from 2 hospitals in Singapore. A total of 86 EQ-5D-5L health states (10 per patient) were valued using a composite time trade-off method according to the international valuation protocol for EQ-5D-5L; 20-parameter linear models and 8-parameter cross-attribute level effects models with and without an N45 term (indicating whether any health state dimension at level 4 or 5 existed) were estimated. Each model included patient-specific random intercepts. Model performance was evaluated for out-of-sample and in-sample predictive accuracy in terms of root mean square error. The discriminative ability of the utility values was assessed using heart disease-related functional classes.

RESULTS

A total of 576 patients were included in the analysis. The preferred model, with the lowest out-of-sample root mean square error, was a 20-parameter linear model including N45. Predicted utility values ranged from -0.727 for the worst state to 1 for full health; the value for the second-best state was 0.981. Utility values demonstrated good discriminative ability in differentiating among patients of varied functional classes.

CONCLUSIONS

An EQ-5D-5L value set representing the preferences of patients with heart disease was developed. The value set could be used for patient-centric economic evaluation and health-related quality of life assessment for patients with heart disease.

Associations between Gut Microbiota and Intestinal Inflammation, Permeability and Damage in Young Malawian Children

BACKGROUND

Environmental enteric dysfunction (EED) is common in low- and middle-income countries and associated with childhood undernutrition. The composition of gut microbiota has been implicated in the pathogenesis of EED. Our aim was to assess the associations between gut microbiota and EED biomarkers in rural Malawian children. We hypothesized that there would be an inverse association between microbiota maturity and diversity and fecal concentrations of EED biomarkers.

METHODS

We used data from fecal samples collected at 6, 18 and 30 months from 611 children who were followed up during a nutrition intervention trial. The primary time point for analysis was 18 months. Microbiota data were obtained through 16S rRNA sequencing and variables included microbiota maturity and diversity, phylogenetic dissimilarity and relative abundances of individual taxa. EED biomarkers included calprotectin (marker of inflammation), alpha-1 antitrypsin (intestinal permeability) and REG1B (intestinal damage).

RESULTS

There was an inverse association between microbiota maturity and diversity and fecal concentrations of all 3 EED biomarkers at 18 months (p≤0.001). The results were similar at 30 months, while at 6 months inverse associations were found only with calprotectin and alpha-1 antitrypsin concentrations. At 18 months, EED biomarkers were not associated with phylogenetic dissimilarity, but at 6 and 30 months several associations were observed. Individual taxa predicting EED biomarker concentrations at 18 months included several Bifidobacterium and Enterobacteriaceae taxa as well as potentially displaced oral taxa.

CONCLUSIONS

Our findings support the hypothesis of an inverse association between microbiota maturity and diversity and EED in rural Malawian children.

Inclusion of unexposed subjects improves the precision and power of self-controlled case series method

The self-controlled case series is an important method in the studies of the safety of biopharmaceutical products. It uses the conditional Poisson model to make comparison within persons. In models without adjustment for age (or other time-varying covariates), cases who are never exposed to the product do not contribute any information to the estimation. We provide analytic proof and simulation results that the inclusion of unexposed cases in the conditional Poisson model with age adjustment reduces the asymptotic variance of the estimator of the exposure effect and increases power. We re-analysed a vaccine safety dataset to illustrate.

Healthcare worker stress, anxiety and burnout during the COVID-19 pandemic in Singapore: A 6-month multi-centre prospective study

Aim

The long-term stress, anxiety and job burnout experienced by healthcare workers (HCWs) are important to consider as the novel coronavirus disease (COVID-19) pandemic stresses healthcare systems globally. The primary objective was to examine the changes in the proportion of HCWs reporting stress, anxiety, and job burnout over six months during the peak of the pandemic in Singapore. The secondary objective was to examine the extent that objective job characteristics, HCW-perceived job factors, and HCW personal resources were associated with stress, anxiety, and job burnout.

Method

A sample of HCWs (doctors, nurses, allied health professionals, administrative and operations staff; N = 2744) was recruited via invitation to participate in an online survey from four tertiary hospitals. Data were gathered between March-August 2020, which included a 2-month lockdown period. HCWs completed monthly web-based self-reported assessments of stress (Perceived Stress Scale-4), anxiety (Generalized Anxiety Disorder-7), and job burnout (Physician Work Life Scale).

Results

The majority of the sample consisted of female HCWs (81%) and nurses (60%). Using random-intercept logistic regression models, elevated perceived stress, anxiety and job burnout were reported by 33%, 13%, and 24% of the overall sample at baseline respectively. The proportion of HCWs reporting stress and job burnout increased by approximately 1·0% and 1·2% respectively per month. Anxiety did not significantly increase. Working long hours was associated with higher odds, while teamwork and feeling appreciated at work were associated with lower odds, of stress, anxiety, and job burnout.

Conclusions

Perceived stress and job burnout showed a mild increase over six months, even after exiting the lockdown. Teamwork and feeling appreciated at work were protective and are targets for developing organizational interventions to mitigate expected poor outcomes among frontline HCWs.

Influence of red blood cell indices on HbA1c performance in detecting dysglycaemia in a Singapore preconception cohort study

Abnormalities of red blood cell (RBC) indices may affect glycated haemoglobin (HbA1c) levels. We assessed the influence of haemoglobin (Hb) and mean corpuscular volume (MCV) on the performance of HbA1c in detecting dysglycaemia among reproductive aged women planning to conceive. Women aged 18-45 years (n = 985) were classified as normal (12 ≤ Hb ≤ 16 g/dL and 80 ≤ MCV ≤ 100 fL) and abnormal (Hb < 12 g/dL and/or MCV < 80 fL). The Area Under the Receiver Operating Characteristic (AUROC) curve was used to determine the performance of HbA1c in detecting dysglycaemic status (prediabetes and diabetes). There were 771 (78.3%) women with normal RBC indices. The AUROCs for the normal and abnormal groups were 0.75 (95% confidence interval 0.69, 0.81) and 0.80 (0.70, 0.90), respectively, and were not statistically different from one another [difference 0.04 (- 0.16, 0.08)]. Further stratification by ethnicity showed no difference between the two groups among Chinese and Indian women. However, Malay women with normal RBC indices displayed lower AUROC compared to those with abnormal RBC indices (0.71 (0.55, 0.87) vs. 0.98 (0.93, 1.00), p = 0.002). The results suggest that the performance of HbA1c in detecting dysglycaemia was not influenced by abnormal RBC indices based on low Hb and/or low MCV. However, there may be ethnic variations among them.

Ratio estimators of intervention effects on event rates in cluster randomized trials

We consider five asymptotically unbiased estimators of intervention effects on event rates in non‐matched and matched‐pair cluster randomized trials, including ratio of mean counts r1, ratio of mean cluster‐level event rates r2, ratio of event rates r3, double ratio of counts r4, and double ratio of event rates r5. In the absence of an indirect effect, they all estimate the direct effect of the intervention. Otherwise, r1, r2, and r3 estimate the total effect, which comprises the direct and indirect effects, whereas r4 and r5 estimate the direct effect only. We derive the conditions under which each estimator is more precise or powerful than its alternatives. To control bias in studies with a small number of clusters, we propose a set of approximately unbiased estimators. We evaluate their properties by simulation and apply the methods to a trial of seasonal malaria chemoprevention. The approximately unbiased estimators are practically unbiased and their confidence intervals usually have coverage probability close to the nominal level; the asymptotically unbiased estimators perform well when the number of clusters is approximately 32 or more per trial arm. Despite its simplicity, r1 performs comparably with r2 and r3 in trials with a large but realistic number of clusters. When the variability of baseline event rate is large and there is no indirect effect, r4 and r5 tend to offer higher power than r1, r2, and r3. We discuss the implications of these findings to the planning and analysis of cluster randomized trials.

Maternal meal irregularities during pregnancy and lifestyle correlates

Meal regularity can influence metabolic health. However, habits of skipping and delaying meals are rarely studied among pregnant women. This study examined the incidence of maternal meal skipping and meal delaying, and their associated lifestyle patterns during pregnancy. Pregnant women in the second trimester (18-24 weeks' gestation; n = 90) were recruited from the antenatal clinics in KK Women's and Children's Hospital, Singapore, 2019-2020. Data on sociodemographic, lifestyle and dietary habits were collected. Firstly, principal component analysis was used to identify lifestyle patterns. Subsequently, multiple logistic regression model was used to examine the association of lifestyle patterns with meal skipping and delaying. In total, 32 (35.6%) women had irregular meals, in which 25 (27.8%) and 26 (28.9%) women reported meal skipping and meal delaying for at least 3 times a week, respectively. Women with 'poor sleep and emotion' pattern as characterized by higher scores for poor sleep, depression, anxiety, and stress symptoms were associated with higher odds of meal skipping (OR 1.99; 95% CI 1.13, 3.53) and meal delaying (2.50; 1.31, 4.79). 'Sedentary' pattern, as characterized by greater daily time spent on television and screen electronic devices, and 'weight and inactivity' pattern, as characterized by higher BMI and physical inactivity level, were not associated with meal regularity. In this study, almost one-third of women reporting meal irregularities during pregnancy. 'Poor sleep and emotion' pattern is associated with a higher incidence of meal skipping and delaying. These findings suggest the need to address sleep and emotional health in interventions promoting healthy nutrition specifically regular eating in pregnancy.

IMMUNOGENICITY AND IMPACT ON NASOPHARYNGEAL CARRIAGE OF A SINGLE DOSE OF PCV10 GIVEN TO VIETNAMESE CHILDREN AT 18 MONTHS OF AGE

Background

This study investigated the immunogenicity and impact on nasopharyngeal carriage of a single dose of PCV10 given to 18-month-old Vietnamese children. This information is important for countries considering catch-up vaccination during PCV introduction and in the context of vaccination during humanitarian crises.

Methods

Two groups of PCV-naïve children within the Vietnam Pneumococcal Project received PCV10 (n=197) or no PCV (unvaccinated; n=199) at 18 months of age. Blood samples were collected at 18, 19, and 24 months of age, and nasopharyngeal swabs at 18 and 24 months of age. Immunogenicity was assessed by measuring serotype-specific IgG, opsonophagocytosis (OPA) and memory B cells (Bmem). Pneumococci were detected and quantified using real-time PCR and serotyped by microarray.

Findings

At 19 months of age, IgG and OPA responses were higher in the PCV10 group compared with the unvaccinated group for all PCV10 serotypes and cross-reactive serotypes 6A and 19A. This was sustained out to 24 months of age, at which point PCV10-type carriage was 60% lower in the PCV10 group than the unvaccinated group. Bmem levels increased between 18 and 24 months of age in the vaccinated group.

Interpretation

We demonstrate strong protective immune responses in vaccinees following a single dose of PCV10 at 18 months of age, and a potential impact on herd protection through a substantial reduction in vaccine-type carriage. A single dose of PCV10 in the second year of life could be considered as part of catch-up campaigns or in humanitarian crises to protect children at high-risk of pneumococcal disease.

Accuracy incentives and framing effects to minimize the influence of cognitive bias among advanced cancer patients

Many patients with advanced illness have unrealistic survival expectations, largely due to cognitive biases. Studies suggests that when people are motivated to be accurate, they are less prone to succumb to these biases. Using a randomized survey design, we test whether offering advanced cancer patients (n = 200) incentives to estimate their prognosis improves accuracy. We also test whether presenting treatment benefits in terms of a loss (mortality) rather than a gain (survival) reduces willingness to take up a hypothetical treatment. Results are not consistent with the proposed hypotheses for either accuracy incentives or framing effects.

Fecundability in reproductive aged women at risk of sexual dysfunction and associated risk factors: a prospective preconception cohort study

BACKGROUND

Female sexual dysfunction (FSD) is a prevalent problem, affecting up to 41% of reproductive aged women worldwide. However, the association between female sexual function (FSF) and fecundability in women attempting to conceive remains unclear. We aimed 1) to examine the association between FSF in reproductive-aged preconception Asian women and fecundability, as measured by time-to-pregnancy in menstrual cycles, and 2) to examine lifestyle and behavioral factors associated with FSF.

METHODS

From the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO) prospective cohort, we evaluated FSF using the 6-item Female Sexual Function Index (FSFI-6) and ascertained time-to-pregnancy within a year of baseline assessment. We estimated fecundability ratio (FR) and 95% confidence interval (CI) using the discrete-time proportional hazards model, accounting for left-truncation and right censoring. We used multivariable logistic and linear regression models to identify potential factors related to FSF.

RESULTS

Among 513 participants, 58.9% had low FSF as defined by a total FSFI-6 score at or below the median value of 22. Compared to women with high FSF, those with low FSF had a 27% reduction in fecundability (FR 0.73; 95% CI 0.54, 0.99), with adjustment for age, ethnicity, education, parity and body mass index. Overall, the FRs generally reduced with decreasing FSFI-6 scores. Physical activity, obesity, absence of probable depression and anxiety were independently associated with reduced odds of low FSF and increased FSFI-6 scores, after adjusting for sociodemographic characteristics.

CONCLUSIONS

Low FSF is associated with a longer time-to-pregnancy. Early evaluation and optimization of FSF through increased physical activity and optimal mental health may help to improve female fecundity. The finding of obese women having improved FSF remains uncertain which warrants further investigations on plausibly mechanisms. In general, the current finding highlights the importance of addressing FSF in preconception care service for general women, which is currently lacking as part of the fertility promotion effort in the country.

Timeliness of Childhood Vaccination Coverage: the Growing Up in Singapore Towards Healthy Outcomes Study

Studies investigating timeliness for childhood vaccination are limited especially in Asia. We examined the timeliness of vaccine administration and associated factors among infant and young children in Singapore. A total of 782 children born between November 2009 and July 2011 from a prospective cohort in Singapore were studied. Vaccination records from birth to 24 months of age were obtained from the National Immunization Registry of Singapore. Multivariable logistic regression models were performed. By 2 years of age, 92.8% of children in our cohort experienced a delay in receiving 1 or more vaccine doses according to the recommended national immunization schedule. When vaccinations were reviewed by series for each vaccine, 15.6% received all vaccine series outside the recommended age ranges. Factors associated with receiving vaccination series outside the recommended ages included maternal aged ≤ 35 years (OR 2.00; 95% CI 1.09, 3.66), Malay (1.71; 1.01, 2.89) or Indian ethnicity (2.06; 1.19, 3.59), low monthly household income (1.91; 1.14, 3.18), having at least four children (3.46; 1.62, 7.38) and private (3.42; 1.80, 6.48) and multiple vaccination providers (3.91; 1.23, 12.48). These findings show an unacceptably high proportion of children experienced a delay in the receipt of their vaccinations. The identification of several demographic, socioeconomic, health-seeking behavioural and vaccine provider factors provides opportunities for targeted interventions to enhance the timeliness of childhood vaccination in Singapore.

Hope, bias and survival expectations of advanced cancer patients: A cross-sectional study

OBJECTIVE

Many patients with advanced illness are unrealistically optimistic about their prognosis. We test for the presence of several cognitive biases, including optimism bias, illusion of superiority, self-deception, misattribution, and optimistic update bias, that could explain unrealistically optimistic prognostic beliefs among advanced cancer patients and quantifies the extent to which hope exacerbates these biases.

METHODS

A cross-sectional survey was administered to 200 advanced cancer patients with physician-estimated prognoses of one year or less. Hope was measured using the Herth Hope Index (HHI). Hypotheses were tested using linear and logistic regressions and a structural-equation model.

RESULTS

Results are consistent with the presence of optimism bias, illusion of superiority, self-deception, and misattribution. All of these biases are amplified by higher levels of hope. Each 1-point higher HHI is associated with a 6% (OR: 1.06; 95% CI: 1.01-1.11) greater odds of believing their illness is curable, a 0.33-year (95% CI: 0.17-0.49) longer expected survival, a 6% (OR: 1.06; 95% CI: 1.02-1.11) higher probability of believing that survival outcomes are better than the average patient, a 5% higher odds of believing primary intent of treatment is curative (OR: 1.05; 95% CI: 1.00-1.10), and a 12% (OR: 1.12; 95% CI: 1.05-1.17) higher odds of believing they are well-informed. Mediation analyses revealed that hope significantly mediates the effect of mental-well-being and loneliness on expected survival.

CONCLUSIONS

Results suggest advanced cancer patients succumb to several cognitive biases which are exacerbated by greater levels of hope. As a result, they are susceptible to possible over-treatment and regret.

Statistical inference in matched case-control studies of recurrent events

BACKGROUND

The concurrent sampling design was developed for case-control studies of recurrent events. It involves matching for time. Standard conditional logistic-regression (CLR) analysis ignores the dependence among recurrent events. Existing methods for clustered observations for CLR do not fit the complex data structure arising from the concurrent sampling design.

METHODS

We propose to break the matches, apply unconditional logistic regression with adjustment for time in quintiles and residual time within each quintile, and use a robust standard error for observations clustered within persons. We conducted extensive simulation to evaluate this approach and compared it with methods based on CLR. We analysed data from a study of childhood pneumonia to illustrate the methods.

RESULTS

The proposed method and CLR methods gave very similar point estimates of association and showed little bias. The proposed method produced confidence intervals that achieved the target level of coverage probability, whereas the CLR methods did not, except when disease incidence was low.

CONCLUSIONS

The proposed method is suitable for the analysis of case-control studies with recurrent events.

Validity and reliability of the English and translated Chinese versions of the Integrated Palliative care Outcome Scale (IPOS) in Singapore

CONTEXT

Measurement of patient-centred outcomes enables clinicians to focus on patient and family priorities and enables quality of palliative care to be assessed.

OBJECTIVES

This study aimed to evaluate the validity and reliability of the English and translated Chinese versions of the Integrated Palliative care Outcome Scale (IPOS) among advanced cancer patients in Singapore.

METHODS

IPOS was forward and backward translated from English into Chinese. Structural validity was assessed by confirmatory factor analysis; known-group validity by comparing inpatients and community patients; construct validity by correlating IPOS with Edmonton Symptom Assessment System-revised (ESAS-r) and Functional Assessment of Cancer Therapy-General (FACT-G); internal consistency by Cronbach's alpha; inter-rater reliability between patient and staff responses; test-retest reliability of patient responses between two timepoints.

RESULTS

One hundred eleven English-responding and 109 Chinese-responding patients participated. The three-factor structure (Physical Symptoms, Emotional Symptoms and Communication and Practical Issues) was confirmed with Comparative Fit Index and Tucker-Lewis-Index > 0.9 and Root Mean Square Error of Approximation < 0.08. Inpatients scored higher than outpatients as hypothesised. Construct validity (Pearson's correlation coefficient, r ≥ |0.608|) was shown between the related subscales of IPOS and FACT-G and ESAS-r. Internal consistency was confirmed for total and subscale scores (Cronbach's alpha≥0.84), except for the Communication and Practical Issues subscale (Cronbach's alpha = 0.29-0.65). Inter-rater reliability (Intra-class correlation coefficient [ICC] ≤ 0.43) between patient and staff responses was insufficient. Test-retest reliability was confirmed with Intra-class correlation coefficient ICC = 0.80 (English) and 0.88 (Chinese) for IPOS Total.

CONCLUSION

IPOS in English and Chinese showed good validity, good internal consistency, and good test-retest reliability, except for the Communication and Practical Issues subscale. There was poor inter-rater reliability between patients and staff.

Faecal regenerating 1B protein concentration is not associated with child growth in rural Malawi

AIM

This study was designed to determine whether faecal regenerating 1B protein (REG1B) concentration is associated with physical growth among 6-30-month-old children in rural Malawi.

METHODS

This was a secondary analysis from a randomised controlled trial in rural Malawi in which we followed-up 790 live-born infants from birth to 30 months of age. We collected anthropometric data at the age of 6, 12, 18, 24 and 30 months. We measured faecal REG1B concentration by enzyme-linked immunosorbent assay (ELISA) technique using stool samples collected at 6, 18 and 30 months of age. We assessed the association between faecal REG1B concentration and children's physical growth using linear regression and longitudinal data analysis.

RESULTS

Of 790 live-born infants enrolled, 694 (87%) with at least one faecal REG1B concentration measurement were included in the analysis. Faecal REG1B concentration was not associated with the children's concurrent length-for-age z-score (LAZ), weight-for-age z-score (WAZ), weight-for-length z-score (WLZ) and mid-upper arm circumference-for-age z-score (MUACZ) at any time point (P > 0.05), nor with a change in their anthropometric indices in the subsequent 6-month period (P > 0.05).

CONCLUSIONS

Faecal REG1B concentration is not associated with LAZ, WAZ, WLZ and MUACZ among 6-30-month-old infants and children in rural Malawi.

Reference values for the short forms of the Singapore Caregiver Quality of Life Scale

PURPOSE

The 15- and 10-item short forms of the Singapore Caregiver Quality of Life Scale (SCQOLS-15 and SCQOLS-10) were recently developed as a quick assessment of caregiver quality of life. Reference values describing the distribution of the total and domain scores are available for the full-length version, but they are not yet available for the short forms. This study aimed to estimate the reference values for the short forms.

METHODS

Data from a cross-sectional survey of 612 family caregivers of patients with advanced cancer in Singapore were fitted in quantile regression models. Percentiles were estimated by regressing the short forms' scores on caregiver characteristics. Classification by the reference values for the short forms and the full-length version were compared and agreement was evaluated.

RESULTS

The caregiver's role in caring for the patient and the patient's performance status were associated with the percentiles of the total scores and most domain scores (each Bonferroni-adjusted p-value, P_B, < 0.05). Higher-educated caregivers were categorized into higher percentiles according to the SCQOLS-15 and SCQOLS-10 total scores and the SCQOLS-15 Mental Well-being and Financial Well-being domain scores (each P_B < 0.05). Ethnicity was associated with the SCQOLS-15 Physical Well-being and Experience & Meaning domains (each P_B < 0.05). The percentiles for the short forms showed moderate to substantial agreement with those for the full-length version in terms of classifying caregivers into percentile intervals (quadratic-weighted Kappa = 0.72 to 0.92).

CONCLUSION

Reference values for the SCQOLS-15 and SCQOLS-10 were estimated in relation to caregiver characteristics to facilitate interpretation of the short form scores.

The Feasibility and Acceptability of a Cognitive Behavioral Therapy-Based Intervention for Patients With Advanced Colorectal Cancer

CONTEXT

Advanced colorectal cancer and its treatment can bring about challenges associated with psychological distress.

OBJECTIVES

The primary aims of this study were to examine the feasibility and acceptability of a cognitive behavioral therapy (CBT)-based intervention to improve coping with the disease. The secondary aim is to evaluate preliminary intervention efficacy.

METHODS

Patients with advanced colorectal cancer in Singapore (N = 60) were randomized to either receive a four-session CBT intervention immediately or be waitlisted. Intervention feasibility (i.e., recruitment and intervention adherence) and acceptability (i.e., participant satisfaction and cultural sensitivity) were assessed. Changes in psychological distress and self-efficacy were examined.

RESULTS

The study successfully recruited the intended sample (mean age 61; 62% men). A proportion (12%) reported Hospital Anxiety and Depression Scale scores indicative of distress at baseline. Most (88%) completed all sessions. Participants reported high rates of satisfaction (97%), helpfulness (96%), and cultural sensitivity (95%) of the intervention. The intervention group did not show decrease in psychological distress; however, self-efficacy in cancer-related coping (information seeking: effect size [ES] = 0.64; 95% CI = 0.17, 0.85; coping with side effects: ES = 0.69; 95% CI = 0.33, 0.82; and maintaining positive attitude: ES = 0.45; 95% CI = 0.19, 0.79) increased in the intervention group compared with the waitlisted group.

CONCLUSION

The CBT-based intervention was feasible and acceptable to patients in Singapore. There is no sufficient evidence to warrant a larger trial in this sample with low baseline distress. Future work should identify and target those who are most in need of support.

Development and evaluation of the Singapore Caregiver Quality of Life Scale - Dementia

PURPOSE

To develop and evaluate a measurement scale for multi-domain assessment of the quality of life of family caregivers of persons with dementia (PWD) in Singapore, a multi-ethic society in South-East Asia where English is the lingua franca.

METHODS

Items from the Singapore Caregiver Quality of Life Scale (SCQOLS), which was originally developed in the context of advanced cancers, were adopted as candidate items. Furthermore, a multi-disciplinary panel reviewed dementia-specific caregiver quality of life scales to identified items not covered in SCQOLS for inclusion as candidate items. A pilot study of 31 family caregivers of PWD was conducted to solicit inputs on candidate items; 102 family caregivers of PWD were surveyed for evaluation of the scale's measurement properties.

RESULTS

Factor analysis confirmed a 5-domain structure of the 63 candidate items. The Root Mean Square Error of Approximation was 0.056 and Comparative Fit Index was 0.928. Convergent validity of the total and domain scores was demonstrated in terms of correlation with the Brief Assessment Scale for Caregivers and its sub-scales. The scores also showed an expected pattern of correlation with hours spent on caregiving per week. Known-group validity was demonstrated by differences in mean scores between functional staging groups. Cronbach's alpha of the total and domain scores ranged from 0.89 to 0.95. Test-retest reliability (intraclass correlation coefficient) ranged from 0.77 to 0.92.

CONCLUSIONS

The Singapore Caregiver Quality of Life Scale - Dementia (SCQOLS-D) is a quality of life measurement scale for family caregivers of persons with dementia that is valid and reliable.

Exploring the Score Equivalence of the English and Chinese Versions of the Brief Assessment Scale for Caregivers

Background:

Multilingual outcome measures are used so that research studies are more generalizable across language contexts.

Objective:

To determine the score equivalence of the English and Chinese versions of Brief Assessment Scale for Caregivers (BASC) in Singapore.

Method:

Caregivers of patients with advanced cancer completed the BASC in either English or Chinese. Multivariable linear regression analysis was used to compare the mean BASC total and factor scores between the 2 language versions, with adjustment for possible confounding variables. Equivalence was declared if the 90% confidence interval of the mean scores fell entirely within an equivalence zone of ±0.5 standard deviation.

Results:

There were 521 ethnic Chinese participants, of whom 214 answered the English version and 307 answered the Chinese version. The BASC total and factor scores met the criteria for equivalence. Cronbach α coefficients were similar and exploratory factor analysis showed similar 2-factor structures for both language versions.

Conclusion:

The English and Chinese versions of the BASC were found to be equivalent in terms of similar adjusted mean scores, Cronbach α, and factor structures.

Estimation of the primary, secondary and composite effects of malaria vaccines using data on multiple clinical malaria episodes

BACKGROUND

An effective malaria vaccine affects the risk of malaria directly, through the vaccine-induced immune response (the primary effect), and indirectly, as a consequence of reduced exposure to malaria infection and disease, leading to slower acquisition of natural immunity (the secondary effect). The beneficial primary effect may be offset by a negative secondary effect, resulting in a smaller or nil composite effect. Reports of malaria vaccine trials usually present only the composite effect. We aimed to demonstrate how the primary and secondary effects can also be estimated from trial data.

METHODS

We propose an enhancement to the conditional frailty model for the estimation of primary effect using data on disease episodes. We use the Andersen-Gill model to estimate the composite effect. We consider taking the ratio of the hazard ratios to estimate the secondary effect. We used directed acyclic graphs and data from a randomized trial of the RTS,S/AS02 malaria vaccine to illustrate the problems and solutions. Time-varying effects were estimated by partitioning the follow-up into four time periods.

RESULTS

The primary effect estimates from our proposed model were consistently stronger than the conditional frailty model in the existing literature. The primary effect of the vaccine was consistently stronger than the composite effect across all time periods. Both the primary and composite effects were stronger in the first three months, with hazard ratios (95% confidence interval) 0.62 (0.49-0.79) and 0.68 (0.54-0.84), respectively; the hazard ratios weakened over time. The secondary effect appeared mild, with hazard ratio 1.09 (1.02-1.16) in the first three months.

CONCLUSIONS

The proposed analytic strategy facilitates a more comprehensive interpretation of trial data on multiple disease episodes. The RTS,S/AS02 vaccine had modest primary and secondary effects that waned over time, but the composite effect in preventing clinical malaria remained positive up to the end of the study.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov NCT00197041.

Calibration of a physical functioning item bank for measurement of health-related quality of life in Singapore

PURPOSE

We aimed to develop and calibrate an item bank to measure physical function (PF) in Singapore, a multi-ethnic city in Southeast Asia.

METHODS

We recruited participants from community and hospital settings stratified for age and gender, with and without medical conditions to administer candidate pool of 61-items derived from the people's perspectives. We calibrated their responses using Samejima's graded response model of item response theory (IRT), including model assumptions, model fit, differential item functioning (DIF), and concurrent and known-groups validity.

RESULTS

496 participants (50% male; 41% above 50 years old; 33.3% Chinese, 32.7% Malay and 34.1% Indian; 35% without chronic illness) were included in the calibration of item bank. 6 items were excluded due to mis-fit and local dependence. Redundancies in the response level was collapsed and re-scoring, while preserving the 5-level response structure. We found the final 55-item PF bank had adequate fit to IRT assumptions of unidimensionality, local independence and monotonicity. Items generally showed discernible ceiling effects with latent scores between - 3.5 to + 1.5. We found no DIF with gender, ethnicity or education. The PF scores correlated in the hypothesized direction with self-reported global health (Spearman's rho =  - 0.35, 95% confidence intervals - 0.43 to - 0.27) and discriminated between groups stratified by age, gender and medical conditions.

CONCLUSION

The 55-item Singapore PF item bank provides an adequate tool for measuring the lower end of PF, with greatest potential utility in healthcare settings where restoration to normal physical functioning is the goal of intervention.

Reference values for and interpretation of the Singapore Caregiver Quality of Life Scale: a quantile regression approach

PURPOSE

The Singapore Caregiver Quality of Life Scale (SCQOLS) was recently developed and validated in two languages - English and Chinese. The total and domain scores are scaled to range from 0 to 100. However, the scale is not at the interval-ratio level of measurement. To facilitate interpretation, we established the percentiles of the scale's total and domain scores among family caregivers of patients with advanced cancers and demonstrate the effect size in terms of differences in relation to caregiver and patient characteristics.

METHODS

Data were drawn from a cross-sectional survey of family caregivers of patients with stage III or IV solid cancers in Singapore. Quantile regression was used to estimate the percentiles in relation to caregiver and patient characteristics.

RESULTS

Participants in adjacent categories of patient's performance status and caregiver's having other family members to share caregiving duties differed by 3 to 5 points in median quality of life total score and most domain scores (each Bonferroni-adjusted P, P[B], < 0.05). Ethnicity was associated with the Physical Well-being and Experience & Meaning domain scores (each P[B] < 0.05), with variable direction and magnitude. Education was associated with Mental Well-being and Financial Well-being (each P[B] < 0.05). Equations and examples for calculation of the percentiles are provided.

CONCLUSION

Percentiles and effect size estimates are provided to facilitate interpretation of the SCQOLS.

Environmental exposures and child and maternal gut microbiota in rural Malawi

BACKGROUND

Gut microbiota composition is associated with child health, but the effect of the environment on microbiota composition is not well understood. Few studies have been conducted in low-income settings where childhood malnutrition is common and possibly related to microbiota composition.

OBJECTIVES

To investigate whether gut microbiota composition in young children and their mothers is associated with different environmental exposures in rural Malawi. We hypothesized that more adverse environmental exposures would be associated with lower levels of microbiota maturity and diversity.

METHODS

Faecal samples from up to 631 children and mothers participating in a nutrition intervention trial were collected at 1, 6, 12, 18, and 30 months (children) and at 1 month (mothers) after birth and analysed for microbiota composition with 16S rRNA sequencing. Bacterial OTU and genus abundances, measures of microbiota maturity and diversity, and UniFrac distances were compared between participants with different environmental exposures. The exposure variables included socio-economic status, water source, sanitary facility, domestic animals, maternal characteristics, season, antibiotic use, and delivery mode.

RESULTS

Measures of microbiota maturity and diversity in children were inversely associated with maternal education at 6, 18, and 30 months and did not otherwise differ consistently between participants with different environmental exposures. Phylogenetic distance was related to season of stool sample collection at all time points. At the level of individual OTUs and genera, season of stool sample collection, type of water source, and maternal education showed most associations with child gut microbiota, while HIV status was the most important predictor of relative OTU and genus abundances in mothers.

CONCLUSION

The results do not support the hypothesis that adverse environmental exposures are broadly associated with lower microbiota maturity and diversity but suggest that environmental exposures influence the abundance of several bacterial OTUs and genera and that low maternal education is associated with higher microbiota maturity and diversity.

A feasible and acceptable multicultural psychosocial intervention targeting symptom management in the context of advanced breast cancer

OBJECTIVE

Advanced breast cancer patients around the world experience high symptom burden (ie, distress, pain, and fatigue) and are in need of psychosocial interventions that target symptom management. This study examined the feasibility, acceptability, and engagement of a psychosocial intervention that uses cognitive-behavioral strategies along with mindfulness and values-based activity to enhance patients' ability to manage symptoms of advanced disease in a cross-cultural setting (United States and Singapore). Pre-treatment to post-treatment outcomes for distress, pain, and fatigue were compared between intervention recipients and waitlisted controls.

METHODS

A pilot randomized controlled trial included women with advanced breast cancer (N = 85) that were recruited in the United States and Singapore. Participants either received the four session intervention or be put on waitlist. Descriptive statistics and effect size of symptom change were calculated.

RESULTS

The psychosocial intervention was found to be feasible as indicated through successful trial accrual, low study attrition (15% ), and high intervention adherence (77% completed all sessions). Acceptability (ie, program satisfaction and cultural sensitivity) and engagement to the study intervention (ie, practice of skills taught) were also high. Anxiety, depression, and fatigue scores remained stable or improved among intervention participants while the same symptoms worsened in the control group. In general, effect sizes are larger in the US sample compared with the Singapore sample.

CONCLUSIONS

The cognitive-behavioral, mindfulness, and values-based intervention is feasible, acceptable, and engaging for advanced breast cancer patients in a cross-cultural setting and has potential for efficacy. Further larger-scaled study of intervention efficacy is warranted.

Developing item banks to measure three important domains of health-related quality of life (HRQOL) in Singapore

Objectives

To develop separate item banks for three health domains of health-related quality of life (HRQOL) ranked as important by Singaporeans – physical functioning, social relationships, and positive mindset.

Methods

We adapted the Patient Reported Outcomes Measurement Information System Qualitative Item Review protocol, with input and endorsement from laymen and experts from various relevant fields. Items were generated from 3 sources: 1) thematic analysis of focus groups and in-depth interviews for framework (n = 134 participants) and item(n = 52 participants) development, 2) instruments identified from a literature search (PubMed) of studies that developed or validated a HRQOL instrument among adults in Singapore, 3) a priori identified instruments of particular relevance. Items from these three sources were “binned” and “winnowed” by two independent reviewers, blinded to the source of the items, who harmonized their selections to generate a list of candidate items (each item representing a subdomain). Panels with lay and expert representation, convened separately for each domain, reviewed the face and content validity of these candidate items and provided inputs for item revision. The revised items were further refined in cognitive interviews.

Results

Items from our qualitative studies (51 physical functioning, 44 social relationships, and 38 positive mindset), the literature review (36 instruments from 161 citations), and three a priori identified instruments, underwent binning, winnowing, expert panel review, and cognitive interview. This resulted in 160 candidate items (61 physical functioning, 51 social relationships, and 48 positive mindset).

Conclusions

We developed item banks for three important health domains in Singapore using inputs from potential end-users and the published literature. The next steps are to calibrate the item banks, develop computerized adaptive tests (CATs) using the calibrated items, and evaluate the validity of test scores when these item banks are administered adaptively.