Measuring the burden of common morbidities: sampling disease experience versus continuous surveillance

Supplementation with Small-Quantity Lipid-Based Nutrient Supplements Does Not Increase Child Morbidity in a Semiurban Setting in Ghana: A Secondary Outcome Noninferiority Analysis of the International Lipid-Based Nutrient Supplements (iLiNS)-DYAD Randomized Controlled Trial

BACKGROUND

Adequate knowledge about the safety of consumption of small-quantity lipid-based nutrient supplements (SQ-LNSs) is needed.

OBJECTIVE

We aimed to test the hypothesis that SQ-LNS consumption is noninferior to control with respect to child morbidity.

METHODS

Women (n = 1320) ≤20 wk pregnant were assigned to iron and folic acid until delivery with no supplementation for offspring; or multiple micronutrient supplements until 6 mo postpartum with no supplementation for offspring; or SQ-LNSs until 6 mo postpartum, and SQ-LNSs for offspring (6 mg Fe/d) from 6 to 18 mo of age [the lipid-based nutrient supplement (LNS) group]. We assessed noninferiority (margin ≤20%) between any 2 groups during 0-6 mo of age, and between the non-LNS and LNS groups during 6-18 mo of age for caregiver-reported acute respiratory infection, diarrhea, gastroenteritis, fever/suspected malaria, poor appetite, and "other illnesses."

RESULTS

During 0-6 mo of age, 1197 infants contributed 190,503 infant-days. For all morbidity combined, overall mean incidence (per 100 infant-days) was 3.3 episodes, overall mean prevalence (percentage of infant-days) was 19.3%, and the 95% CIs of the incidence rate ratio (IRR) and longitudinal prevalence rate ratio (LPRR) between any 2 groups were ≤1.20. During 6-18 mo, there were 240,097 infant-days for the non-LNS group and 118,698 for the LNS group. For all morbidity combined, group mean incidences were 4.3 and 4.3, respectively (IRR: 1.0; 95% CI: 1.0, 1.1), and mean prevalences were 28.2% and 29.3%, respectively (LPRR: 1.0; 95% CI: 1.0, 1.1). Noninferiority was inconclusive for diarrhea, fever/suspected malaria, and poor appetite.

CONCLUSIONS

SQ-LNS consumption does not increase reported overall child morbidity in this population compared with the 2 other treatments.This trial was registered at clinicaltrials.gov as NCT00970866.

Lipid-based nutrient supplements do not affect the risk of malaria or respiratory morbidity in 6- to 18-month-old Malawian children in a randomized controlled trial

BACKGROUND

There is evidence to support the use of lipid-based nutrient supplements (LNSs) to promote child growth and development in low-income countries, but there is also a concern regarding the safety of using iron-fortified products in malaria-endemic areas.

OBJECTIVE

The objective of this study was to test the hypothesis that 6- to 18-mo-old rural Malawian children receiving iron-containing (6 mg/d) LNSs would not have excess morbidity compared with infants receiving no supplementation.

METHODS

A randomized controlled trial allocated 840 children to receive daily supplementation with 54 g/d LNS with milk protein base (milk-LNS), 54 g/d LNS with soy protein base (soy-LNS), 71 g/d corn-soy blend (CSB), or no supplementation from 6 to 18 mo of age. Morbidity was compared using a non-inferiority margin set at 20% excess morbidity in supplemented groups compared with the nonsupplemented group.

RESULTS

Baseline characteristics were similar across groups. The proportion of days with febrile illness between 6 and 18 mo was 4.9%, and there were no differences between the groups: 4.9% (95% CI: 4.3, 5.5%), 4.5% (95% CI: 3.9, 5.1%), 4.7% (95% CI: 4.1, 5.3%), and 5.5% (95% CI: 4.7-6.3%) in the milk-LNS, soy-LNS, CSB, and control groups, respectively. The proportion of days with respiratory problems and diarrhea between 6 and 18 mo also did not differ between groups. Compared with controls, the incident rate ratio (95% CI) for clinical malaria was 0.80 (0.59, 1.09), 0.77 (0.56, 1.06), and 0.79 (0.58, 1.08) in milk-LNS, soy-LNS, and CSB, respectively, with 95% CIs confirming non-inferiority. The incidence of febrile episodes, diarrhea, respiratory problems or admission to hospital, prevalence of malaria parasitemia throughout the follow-up, and mean change in hemoglobin concentration from baseline were also similar between the groups.

CONCLUSIONS

Daily supplementation with 54 g of milk-based or soy protein-based LNS or 71 g of CSB did not result in increases in malaria or respiratory morbidity in children in a malaria-endemic setting. However, we could not conclude whether LNSs did or did not increase diarrheal morbidity. This trial was registered at clinicaltrials.gov as NCT00524446.

Cluster-randomised controlled trials of individual and combined water, sanitation, hygiene and nutritional interventions in rural Bangladesh and Kenya: the WASH Benefits study design and rationale

INTRODUCTION

Enteric infections are common during the first years of life in low-income countries and contribute to growth faltering with long-term impairment of health and development. Water quality, sanitation, handwashing and nutritional interventions can independently reduce enteric infections and growth faltering. There is little evidence that directly compares the effects of these individual and combined interventions on diarrhoea and growth when delivered to infants and young children. The objective of the WASH Benefits study is to help fill this knowledge gap.

METHODS AND ANALYSIS

WASH Benefits includes two cluster-randomised trials to assess improvements in water quality, sanitation, handwashing and child nutrition-alone and in combination-to rural households with pregnant women in Kenya and Bangladesh. Geographically matched clusters (groups of household compounds in Bangladesh and villages in Kenya) will be randomised to one of six intervention arms or control. Intervention arms include water quality, sanitation, handwashing, nutrition, combined water+sanitation+handwashing (WSH) and WSH+nutrition. The studies will enrol newborn children (N=5760 in Bangladesh and N=8000 in Kenya) and measure outcomes at 12 and 24 months after intervention delivery. Primary outcomes include child length-for-age Z-scores and caregiver-reported diarrhoea. Secondary outcomes include stunting prevalence, markers of environmental enteropathy and child development scores (verbal, motor and personal/social). We will estimate unadjusted and adjusted intention-to-treat effects using semiparametric estimators and permutation tests.

ETHICS AND DISSEMINATION

Study protocols have been reviewed and approved by human subjects review boards at the University of California, Berkeley, Stanford University, the International Centre for Diarrheal Disease Research, Bangladesh, the Kenya Medical Research Institute, and Innovations for Poverty Action. Independent data safety monitoring boards in each country oversee the trials. This study is funded by a grant from the Bill & Melinda Gates Foundation to the University of California, Berkeley.

REGISTRATION

Trial registration identifiers (http://www.clinicaltrials.gov): NCT01590095 (Bangladesh), NCT01704105 (Kenya).

Epidemiological methods in diarrhoea studies--an update

BACKGROUND

Diarrhoea remains a leading cause of morbidity and mortality but is difficult to measure in epidemiological studies. Challenges include the diagnosis based on self-reported symptoms, the logistical burden of intensive surveillance and the variability of diarrhoea in space, time and person.

METHODS

We review current practices in sampling procedures to measure diarrhoea, and provide guidance for diarrhoea measurement across a range of study goals. Using 14 available data sets, we estimated typical design effects for clustering at household and village/ neighbourhood level, and measured the impact of adjusting for baseline variables on the precision of intervention effect estimates.

RESULTS

Incidence is the preferred outcome measure in aetiological studies, health services research and vaccine trials. Repeated prevalence measurements (longitudinal prevalence) are appropriate in high-mortality settings where malnutrition is common, although many repeat measures are rarely useful. Period prevalence is an inadequate outcome if an intervention affects illness duration. Adjusting point estimates for age or diarrhoea at baseline in randomized trials has little effect on the precision of estimates. Design effects in trials randomized at household level are usually <2 (range 1.0–3.2). Design effects for larger clusters (e.g. villages or neighbourhoods) vary greatly among different settings and study designs (range 0.1–25.8).

CONCLUSIONS

Using appropriate sampling strategies and outcome measures can improve the efficiency, validity and comparability of diarrhoea studies. Allocating large clusters in cluster randomized trials is compromized by unpredictable design effects and should be carried out only if the research question requires it.

The burden of common infectious disease syndromes at the clinic and household level from population-based surveillance in rural and urban Kenya

BACKGROUND

Characterizing infectious disease burden in Africa is important for prioritizing and targeting limited resources for curative and preventive services and monitoring the impact of interventions.

METHODS

From June 1, 2006 to May 31, 2008, we estimated rates of acute lower respiratory tract illness (ALRI), diarrhea and acute febrile illness (AFI) among >50,000 persons participating in population-based surveillance in impoverished, rural western Kenya (Asembo) and an informal settlement in Nairobi, Kenya (Kibera). Field workers visited households every two weeks, collecting recent illness information and performing limited exams. Participants could access free high-quality care in a designated referral clinic in each site. Incidence and longitudinal prevalence were calculated and compared using Poisson regression.

RESULTS

INCIDENCE RATES RESULTING IN CLINIC VISITATION WERE THE FOLLOWING: ALRI--0.36 and 0.51 episodes per year for children <5 years and 0.067 and 0.026 for persons ≥ 5 years in Asembo and Kibera, respectively; diarrhea--0.40 and 0.71 episodes per year for children <5 years and 0.09 and 0.062 for persons ≥ 5 years in Asembo and Kibera, respectively; AFI--0.17 and 0.09 episodes per year for children <5 years and 0.03 and 0.015 for persons ≥ 5 years in Asembo and Kibera, respectively. Annually, based on household visits, children <5 years in Asembo and Kibera had 60 and 27 cough days, 10 and 8 diarrhea days, and 37 and 11 fever days, respectively. Household-based rates were higher than clinic rates for diarrhea and AFI, this difference being several-fold greater in the rural than urban site.

CONCLUSIONS

Individuals in poor Kenyan communities still suffer from a high burden of infectious diseases, which likely hampers their development. Urban slum and rural disease incidence and clinic utilization are sufficiently disparate in Africa to warrant data from both settings for estimating burden and focusing interventions.

Evaluation of the optimal recall period for disease symptoms in home-based morbidity surveillance in rural and urban Kenya

Background In African settings with poor access to health care, surveillance and surveys of disease burden are often done through home visits. The optimal recall period to capture data on symptoms and health utilization is unknown.

Methods We collected illness data among 53 000 people during fortnightly home visits in rural and urban Kenya. Dates of cough, fever and diarrhoea in the past 2 weeks and health-seeking behaviour were recorded. Incidence rates were modelled using Poisson regression for data collected from 1 July 2006 to 30 June 2007.

Results Incidence rates were higher in days 0–6 before the home visit than in days 7–13 before the home visit for all three symptoms, for the rural and urban sites, for children and adults, for self- and proxy-reported symptoms and for severe and non-severe illness in children. Recall decay was steeper in the rural than the urban sites, and for proxy- than self-reported symptoms. The daily prevalence of symptoms fell <80% of the maximum prevalence when asking about symptoms >3 days before the home visit for children and >4 days for persons ≥5 years of age. Recall of previously documented clinic visits, and prescriptions of antimalarials and antibiotics also declined by ∼7, 15 and 23% per week, respectively, in children aged <5 years, and 6, 20 and 16%, respectively, in older persons (P < 0.0001 for each decline).

Conclusions A 2-week recall period underestimates true disease rates and health-care utilization. Shorter recall periods of 3 days in children and 4 days in adults would likely yield more accurate data.

Linear growth in early life is associated with suicidal ideation in 18-year-old Filipinos

Studies in Western societies have shown some evidence that growth in early life may be associated with suicide and suicidal ideation in later life. The pattern of growth retardation in developing countries is different from that in Western societies. This study examines the association between size at birth, postnatal growth from birth to age 24 months and suicidal ideation in 18-year-old Filipinos. The 1941 participants born in 1983 and 1984 in the Philippines were assessed for growth status bimonthly from birth to 24 months of age and were administered an interview in 2002, which included items on suicidal ideation. The pattern of growth stunting in this cohort was similar to that in many other developing countries: a minor level of shortness in crown-heel length at birth followed by sharp decline in length-for-age in the first 24 months of life. The prevalence of suicidal ideation at age 18 was 2.9%; 95% confidence interval [CI] 2.2, 3.8%. Length Z-score at 24 months (odds ratios [OR] = 0.67; 95% CI [0.52, 0.86]; P = 0.002) and gain in length Z-score from birth to age 24 months (OR = 0.74; 95% CI [0.56, 0.98]; P = 0.037) were inversely associated with the odds of suicidal ideation. Adjustment for covariates made little difference. Length at birth Z-score was associated with suicidal ideation only after adjustment for postnatal length gain (OR = 0.61; 95% CI [0.46, 0.80]; P < 0.001). The associations between linear growth in early life and suicidal ideation appeared to be partly mediated by educational attainment. In conclusion, postnatal growth stunting is an important predictor of suicidal ideation in later life. It also affects the association between birth length and suicidal ideation.

A simulation model for diarrhoea and other common recurrent infections: a tool for exploring epidemiological methods

The measurement and analysis of common recurrent conditions such as diarrhoea, respiratory infections or fever pose methodological challenges with regard to case definition, disease surveillance and statistical analysis. In this paper we describe a flexible and robust model that can generate simulated longitudinal datasets for a range of recurrent infections, reflecting the stochastic processes that underpin the data collected in the field. It can be used to evaluate and compare alternative disease definitions, surveillance strategies and statistical methods under ‘controlled conditions’. Parameters in the model include: characterizing the distributions of the individual disease incidence and the duration of disease episodes; allowing the average disease duration to depend on an individual's number of episodes (simulating a correlation between incidence and duration); making the individual risk of disease depend on the occurrence of previous episodes (simulating autocorrelation of successive episodes); finally, incorporating seasonal variation of disease.

Estimating the longitudinal prevalence of diarrhea and other episodic diseases: continuous versus intermittent surveillance

BACKGROUND

Longitudinal prevalence (ie, the proportion of time with the disease) is used to describe morbidity from diarrhea and other episodic conditions. The aim of this analysis was to compare estimates of longitudinal prevalence based on intermittent sampling at regular intervals with 24- or 48-hour recall, with estimates based on continuous surveillance.

METHODS

Based on 2 real datasets from Brazil and Guatemala, we developed a simulated dataset representing the diarrhea morbidity of 10,000 individuals followed over 365 days.

RESULTS

Both the model and the real datasets showed that the standard deviation of the longitudinal prevalence increases with decreasing numbers of days sampled, so that a study sampling only a fraction of days would require a larger sample size. However, due to the correlation of diarrhea between consecutive days, sampling at 7- to 14-day intervals results in relatively small loss of precision and power compared with daily morbidity records, especially when the average diarrheal episode is long. A study based on morbidity data for every seventh day may require only a 5%-24% larger sample size than a study with daily records, depending on the average duration of episodes. Using a recall period of 48 hours instead of 24 hours increases power if the average episode is short.

CONCLUSIONS

The results question the necessity of continuous surveillance to estimate longitudinal prevalence. In addition to savings in cost and staff time, intermittent sampling of morbidity may improve validity by minimizing recall error and reducing the influence of surveillance on participants' behavior.

Growth trajectories are influenced by breast-feeding and infant health in an afro-colombian community

We conducted a longitudinal study among an Afro-Colombian population to investigate the influence of feeding practices and child morbidity on linear and ponderal growth during infancy. We enrolled 133 children at 5-7 mo and followed them until 18 mo. Repeated anthropometric measures were taken every 2-3 mo, with monthly interviews on feeding practices and daily self-reports on morbid conditions by the mothers of the infants. Mothers' social conditions and infants' fixed variables (gender and gestational age at birth) were measured at baseline. Growth starting points and trajectories were modeled via Hierarchical Linear Models (HLM). Children started with a mean length of 64.8 cm (95% CI: 59.8-69.7) and a mean weight of 7.68 kg (95% CI: 5.37-9.9), and gained length at a rate of 1.13-1.70 cm/mo, and weight at 66.5-319 g/mo. Breast-feeding, defined as receiving breast milk at any time within a 2-3-mo interval, was positively related to length gain (regression coefficient = 0.27 cm/mo; P = 0.04), after adjusting for social conditions and food consumption. Among mothers with low levels of education, breast-feeding had a positive effect on weight gain (regression coefficient = 0.30 kg/mo; P = 0.04); among nonbreast-fed infants, complementary food diversity generated a positive effect on weight (regression coefficient = 0.14 kg/mo; P = 0.03). Mean differences in length were related to the total proportion of healthy time (regression coefficient = 3.1; P = 0.02), whereas weight-gain rates were negatively associated with changes during illness (regression coefficient = -0.70; P = 0.04 for fever). No association was found between diarrhea episodes and infant growth. Our study confirms that breast-feeding after 6 mo of life is important for nutrition and health, likely by mitigating the negative effects of poor social conditions and diarrhea on infant growth.