A dynamic social relations model for clustered longitudinal dyadic data with continuous or ordinal responses

Social relations models allow the identification of cluster, actor, partner, and relationship effects when analysing clustered dyadic data on interactions between individuals or other units of analysis. We propose an extension of this model which handles longitudinal data and incorporates dynamic structure, where the response may be continuous, binary, or ordinal. This allows the disentangling of the relationship effects from temporal fluctuation and measurement error and the investigation of whether individuals respond to their partner's behaviour at the previous observation. We motivate and illustrate the model with an application to Canadian data on pairs of individuals within families observed working together on a conflict discussion task.

Association between surgical volume and failure of primary total hip replacement in England and Wales: findings from a prospective national joint replacement register

OBJECTIVE

To investigate the association of volume of total hip arthroplasty (THA) between consultants and within the same consultant in the previous year and the hazard of revision using multilevel survival models.

DESIGN

Prospective cohort study using data from a national joint replacement register.

SETTING

Elective THA across all private and public centres in England and Wales between April 2003 and February 2017.

PARTICIPANTS

Patients aged 50 years or more undergoing THA for osteoarthritis.

INTERVENTION

The volume of THA conducted in the preceding 365 days to the index procedure.

MAIN OUTCOME AND MEASURE

Revision surgery (excision, addition or replacement) of a primary THA.

RESULTS

Of the 579 858 patients undergoing primary THA (mean baseline age 69.8 years (SD 10.2)), 61.1% were women. Multilevel survival found differing results for between and within-consultant effects. There was a strong volume-revision association between consultants, with a near-linear 43.3% (95% CI 29.1% to 57.4%) reduction of the risk of revision comparing consultants with volumes between 1 and 200 procedures annually. Changes in individual surgeons (within-consultant) case volume showed no evidence of an association with revision.

CONCLUSION

Separation of between-consultant and within-consultant effects of surgical volume reveals how volume contributes to the risk of revision after THA. The lack of association within-consultants suggests that individual changes to consultant volume alone will have little effect on outcomes following THA.These novel findings provide strong evidence supporting the practice of specialisation of hip arthroplasty. It does not support the practice of low-volume consultants increasing their personal volume as it is unlikely their results would improve if this is the only change. Limiting the exposure of patients to consultants with low volumes of THA and greater utilisation of centres with higher volume surgeons with better outcomes may be beneficial to patients.

Intention, beliefs and mood assessed using electronic diaries predicts attendance at cardiac rehabilitation: An observational study

BACKGROUND

Cardiac rehabilitationis effective in promoting physical/psychological recovery following acute coronary syndrome. Yet, rates of attendance at outpatient cardiac rehabilitation by eligible patients are low.

OBJECTIVES

This study examined the determinants of attendance at outpatient cardiac rehabilitation in acute coronary syndrome patients following discharge until cardiac rehabilitation commencement.

DESIGN

A weekly electronic diary measured cardiac-related cognitions and mood and examined their relation to attendance at outpatient cardiac rehabilitation.

SETTINGS

Three United Kingdom National Health Service secondary care settings in two Health Board areas in Scotland.

PARTICIPANTS

Acute coronary syndrome patients were recruited from March 2012 to June 2013 prior to hospital discharge. Of 488 eligible patients referred for cardiac rehabilitation, 214 consented.

METHODS

Consecutive patients completed a pre-hospital discharge questionnaire targeting age, diagnosis, social class and smoking history. Acute coronary syndrome patients then completed a weekly electronic diary from the first week of discharge until the start of cardiac rehabilitation. Multilevel structural equation models estimated the effects of initial, i.e. baseline and rate of change in cardiac-related cognition and mood on attendance. Intention to attend cardiac rehabilitation was reflected, log transformed, reported thereafter as "do not intend". The role of "do not intend" was explored as a mediator of the relationship between cardiac-related cognition and mood on attendance.

RESULTS

166 participants provided, on average, 5 weeks of diary entries before cardiac rehabilitation commenced. High intention (i.e. low "do not intend") to attend CR and its rate of increase over time predicted attendance. Low negative emotional representation, high perceived necessity, high confidence in maintaining function, low negative affect, and high positive affect following discharge predicted attendance at cardiac rehabilitation. The rate of change in cardiac-related mood and these cognitions was not predictive. Baseline and rate of change in "do not intend" entirely mediated relationships between a) perceived necessity, b) negative affect and attendance at cardiac rehabilitation.

CONCLUSIONS

Negative affect in the first weeks following discharge represents the key challenge to a patient maintaining their intention to attend cardiac rehabilitation. Intervention to improve attendance should focus on improving intention to attend following discharge and during recovery by improving patient understanding of cardiac rehabilitation and reducing negative affect.

A general multilevel multistate competing risks model for event history data, with an application to a study of contraceptive use dynamics

We propose a general discrete time model for multilevel event history data. The model is developed for the analysis of longitudinal repeated episodes within individuals where there are multiple states and multiple types of event (competing risks) which may vary across states. The different transitions are modelled jointly to allow for correlation across transitions in unobserved individual risk factors. Implementation of the methodology using existing multilevel models for discrete response data is described. The model is applied in an analysis of contraceptive use dynamics in Indonesia where transitions from two states, contraceptive use and nonuse, are of interest. A distinction is made between two ways in which an episode of contraceptive use may end: a transition to nonuse or a switch to another method. Before adjusting for covariate effects, there is a strong negative residual correlation between the hazards of a transition from use to nonuse and from nonuse to use; this correlation is due to a tendency for short periods of nonuse after a birth to be followed by long periods of using the same contraceptive method.

Latent variable models for mixed categorical and survival responses, with an application to fertility preferences and family planning in Bangladesh

In this article, we discuss a latent variable model with continuous latent variables for manifest variables that are a mixture of categorical and survival outcomes. Models for censored and uncensored survival data are discussed. The model allows for covariate effects both on the manifest variables (direct effects) and on the latent variable(s) (indirect effects). The methodological developments are motivated by a demographic application: an exploration of women’s fertility preferences and family planning behaviour in Bangladesh.

Joint modelling compared with two stage methods for analysing longitudinal data and prospective outcomes: A simulation study of childhood growth and BP

There is a growing debate with regards to the appropriate methods of analysis of growth trajectories and their association with prospective dependent outcomes. Using the example of childhood growth and adult BP, we conducted an extensive simulation study to explore four two-stage and two joint modelling methods, and compared their bias and coverage in estimation of the (unconditional) association between birth length and later BP, and the association between growth rate and later BP (conditional on birth length). We show that the two-stage method of using multilevel models to estimate growth parameters and relating these to outcome gives unbiased estimates of the conditional associations between growth and outcome. Using simulations, we demonstrate that the simple methods resulted in bias in the presence of measurement error, as did the two-stage multilevel method when looking at the total (unconditional) association of birth length with outcome. The two joint modelling methods gave unbiased results, but using the re-inflated residuals led to undercoverage of the confidence intervals. We conclude that either joint modelling or the simpler two-stage multilevel approach can be used to estimate conditional associations between growth and later outcomes, but that only joint modelling is unbiased with nominal coverage for unconditional associations.

Probabilistic record linkage

Studies involving the use of probabilistic record linkage are becoming increasingly common. However, the methods underpinning probabilistic record linkage are not widely taught or understood, and therefore these studies can appear to be a ‘black box’ research tool. In this article, we aim to describe the process of probabilistic record linkage through a simple exemplar. We first introduce the concept of deterministic linkage and contrast this with probabilistic linkage. We illustrate each step of the process using a simple exemplar and describe the data structure required to perform a probabilistic linkage. We describe the process of calculating and interpreting matched weights and how to convert matched weights into posterior probabilities of a match using Bayes theorem. We conclude this article with a brief discussion of some of the computational demands of record linkage, how you might assess the quality of your linkage algorithm, and how epidemiologists can maximize the value of their record-linked research using robust record linkage methods.

Capturing the temporal sequence of interaction in young siblings

We explored whether young children exhibit subtypes of behavioral sequences during sibling interaction. Ten-minute, free-play observations of over 300 sibling dyads were coded for positivity, negativity and disengagement. The data were analyzed using growth mixture modeling (GMM). Younger (18-month-old) children's temporal behavioral sequences showed a harmonious (53%) and a casual (47%) class. Older (approximately four-year-old) children's behavior was more differentiated revealing a harmonious (25%), a deteriorating (31%), a recovery (22%) and a casual (22%) class. A more positive maternal affective climate was associated with more positive patterns. Siblings' sequential behavioral patterns tended to be complementary rather than reciprocal in nature. The study illustrates a novel use of GMM and makes a theoretical contribution by showing that young children exhibit distinct types of temporal behavioral sequences that are related to parenting processes.

A multilevel simultaneous equations model for within-cluster dynamic effects, with an application to reciprocal parent-child and sibling effects

There has been substantial interest in the social and health sciences in the reciprocal causal influences that people in close relationships have on one another. Most research has considered reciprocal processes involving only 2 units, although many social relationships of interest occur within a larger group (e.g., families, work groups, peer groups, classrooms). This article presents a general longitudinal multilevel modeling framework for the simultaneous estimation of reciprocal relationships among individuals with unique roles operating in a social group. We use family data for illustrative purposes, but the model is generalizable to any social group in which measurements of individuals in the social group occur over time, individuals have unique roles, and clustering of the data is evident. We allow for the possibility that the outcomes of family members are influenced by a common set of unmeasured family characteristics. The multilevel model we propose allows for residual variation in the outcomes of parents and children at the occasion, individual, and family levels and residual correlation between parents and children due to the unmeasured shared environment, genetic factors, and shared measurement. Another advantage of this method over approaches used in previous family research is it can handle mixed family sizes. The method is illustrated in an analysis of maternal depression and child delinquency using data from the Avon Brothers and Sisters Study.

Consequences of family disruption on children's educational outcomes in Norway

Using high-quality data from Norwegian population registers, we examine the relationship between family disruption and children's educational outcomes. We distinguish between disruptions caused by parental divorce and paternal death and, using a simultaneous equation model, pay particular attention to selection bias in the effect of divorce. We also allow for the possibility that disruption may have different effects at different stages of a child's educational career. Our results suggest that selection on time-invariant maternal characteristics is important and works to overstate the effects of divorce on a child's chances of continuing in education. Nevertheless, the experience of marital breakdown during childhood is associated with lower levels of education, and the effect weakens with the child's age at disruption. The effects of divorce are most pronounced for the transitions during or just beyond the high school level. In models that do not allow for selection, children who experienced a father's death appear less disadvantaged than children whose parents divorced. After we control for selection, however differences in the educational qualifications of children from divorced and bereaved families narrow substantially and, at mean ages of divorce, are almost non-existent.

The use of simple reparameterizations to improve the efficiency of Markov chain Monte Carlo estimation for multilevel models with applications to discrete time survival models

We consider the application of Markov chain Monte Carlo (MCMC) estimation methods to random-effects models and in particular the family of discrete time survival models. Survival models can be used in many situations in the medical and social sciences and we illustrate their use through two examples that differ in terms of both substantive area and data structure. A multilevel discrete time survival analysis involves expanding the data set so that the model can be cast as a standard multilevel binary response model. For such models it has been shown that MCMC methods have advantages in terms of reducing estimate bias. However, the data expansion results in very large data sets for which MCMC estimation is often slow and can produce chains that exhibit poor mixing. Any way of improving the mixing will result in both speeding up the methods and more confidence in the estimates that are produced. The MCMC methodological literature is full of alternative algorithms designed to improve mixing of chains and we describe three reparameterization techniques that are easy to implement in available software. We consider two examples of multilevel survival analysis: incidence of mastitis in dairy cattle and contraceptive use dynamics in Indonesia. For each application we show where the reparameterization techniques can be used and assess their performance.

Changing compatibility of cohabitation and childbearing between young British women born in 1958 and 1970

We investigate the effect of parenthood on whether non-marital unions led to marriage or parting for two cohorts of British women when they were aged between 16 and 29. We compare the effect of conceptions leading to births and the presence and characteristics of children on the odds that a cohabitation was dissolved, or that it was converted to marriage, for women born in 1958 and 1970. A multilevel, multiprocess, competing-risks model allows for multiple cohabitation per woman and endogeneity of fertility status. We find that cohabiting couples' response to impending parenthood and the presence of children changed over time. In particular, the proportion of cohabiting couples who married before a birth decreased and, in the 1970 cohort only, the risk of dissolution declined during pregnancy. There is also evidence that the presence of a child cemented a cohabiting union for women from the 1970, but not the earlier, cohort.

The relationship between childbearing and transitions from marriage and cohabitation in Britain

In this article, we describe a general framework for the analysis of correlated event histories, with an application to a study of partnership transitions and fertility among a cohort of British women. Using a multilevel, multistate competing-risks model, we examine the relationship between prior fertility outcomes (the presence and characteristics of children and current pregnancy) and the dissolution of marital and cohabiting unions and movements from cohabitation to marriage. Using a simultaneous-equations model, we model these partnership transitions jointly with fertility, allowing for correlation between the unobserved woman-level characteristics that affect each process. The analysis is based on the partnership and birth histories that were collected for the 1958 birth cohort (National Child Development Study) aged 16–42. The findings indicate that preschool children have a stabilizing effect on their parents’ partnership, whether married or cohabiting, but the effect is weaker for older children. There is also evidence that although pregnancy precipitates marriage among cohabitors, the odds of marriage decline to prepregnancy levels following a birth.

A discrete-time multilevel mixture model for event history data with long-term survivors, with an application to an analysis of contraceptive sterilization in Bangladesh

Event history models typically assume that the entire population is at risk of experiencing the event of interest throughout the observation period. However, there will often be individuals, referred to as long-term survivors, who may be considered a priori to have a zero hazard throughout the study period. In this paper, a discrete-time mixture model is proposed in which the probability of long-term survivorship and the timing of event occurrence are modelled jointly. Another feature of event history data that often needs to be considered is that they may come from a population with a hierarchical structure. For example, individuals may be nested within geographical regions and individuals in the same region may have similar risks of experiencing the event of interest due to unobserved regional characteristics. Thus, the discrete-time mixture model is extended to allow for clustering in the likelihood and timing of an event within regions. The model is further extended to allow for unobserved individual heterogeneity in the hazard of event occurrence. The proposed model is applied in an analysis of contraceptive sterilization in Bangladesh. The results show that a woman's religion and education level affect her probability of choosing sterilization, but not when she gets sterilized. There is also evidence of community-level variation in sterilization timing, but not in the probability of sterilization.

Appropriate methods for analyzing the effect of method choice on contraceptive discontinuation

The contraceptive method chosen is an important determinant of contraceptive discontinuation. However, method choice is endogenous to contraceptive discontinuation. Using data from the 1997 Indonesia Demographic and Health Survey, we apply a multilevel multi-process model to examine the impact of method choice on three types of contraceptive discontinuation. We confirm that method choice is endogenous to the processes of contraceptive abandonment and method switching, but not failure. Ignoring the endogeneity of contraceptive choice leads to various biases in the magnitude of estimated effects of method choice on abandonment and method switching, but the general conclusions are robust to these biases.

The effects of kin on child mortality in rural Gambia

We analyzed data that were collected continuously between 1950 and 1974 from a rural area of the Gambia to determine the effects of kin on child mortality. Multilevel event-history models were used to demonstrate that having a living mother, maternal grandmother, or elder sisters had a significant positive effect on the survival probabilities of children, whereas having a living father, paternal grandmother, grandfather, or elder brothers had no effect. The mother's remarriage to a new husband had a detrimental effect on child survival, but there was little difference in the mortality rates of children who were born to monogamous or polygynous fathers. The implications of these results for understanding the evolution of human life-history are discussed.

Savings/credit group formation and change in contraception

We examine the characteristics of women who chose to join a women's savings or credit group organized by Save the Children USA in a rural area of Bangladesh, and the impact of participation on contraceptive use. The data are taken from a panel survey conducted in 1993, shortly before the groups were formed, and in 1995 after interventions began. Our findings show that although demographic and socioeconomic characteristics have only a weak relationship to the decision to join a program, the treatment that a woman receives from her husband is associated with participation. We also find evidence that the credit program tends to attract women who are already using contraception. The analysis of program impact on the use of modern contraceptives reveals a positive effect of the credit program, after we adjust for this selectivity; we see no evidence of an effect of participation in a savings group.

Pulmonary availability of isotretinoin in rats after inhalation of a powder aerosol

Repeated oral administration of chemopreventive retinoids such as isotretinoin over extended periods of time is associated with intolerable systemic toxicity. Here isotretinoin was formulated as a powder aerosol, and its delivery to the lungs of rats was studied with the aim to explore the possibility of minimizing adverse effects associated with its oral administration. Rats received isotretinoin orally (0.5, 1 or 10 mg kg(-1)) or by inhalation (theoretical dose approximately 1 or approximately 10 mg kg(-1)) in a nose-only inhalation chamber. Isotretinoin was quantitated by high-pressure liquid chromatography in plasma and lung tissue. The ratios of mean area of concentration-vs-time curve (AUC) values in the lungs over mean AUCs in the plasma for isotretinoin following single or repeated aerosol exposure surpassed those determined for the oral route by factors of between two (single low-dose) and five (single high-dose). Similarly, the equivalent ratios for the maximal peak concentrations in lungs and plasma obtained after aerosol exposure consistently exceeded those seen after oral administration, suggesting that lungs were exposed to higher isotretinoin concentrations after aerosol inhalation than after oral administration of similar doses. Repeated high doses of isotretinoin by inhalation resulted in moderate loss of body weight, but microscopic investigation of ten tissues including lung and oesophagus did not detect any significant aerosol-induced damage. The results suggest that administration of isotretinoin via powder aerosol inhalation is probably superior to its application via the oral route in terms of achieving efficacious drug concentrations in the lungs.

Contraceptive switching in Bangladesh

Bangladesh has experienced a substantial decline in fertility that has been achieved by means of a large increase in the use of modern methods of contraception. As contraceptive prevalence increases, aspects of contraceptive-use dynamics, including reasons for discontinuation and behavior after discontinuation, become important influences on fertility. This report uses calendar data from the 1993-94 Bangladesh Demographic and Health Survey to examine contraceptive behavior following discontinuation of modern-method use. The individual-level characteristics found to influence switching behavior include the method used, method-related difficulties with previous contraceptive use, and education. A large amount of unexplained variation in switching rates remains, however, largely at the individual level, but also at the community level for certain types of transition.

The impact of family planning service provision on contraceptive-use dynamics in Morocco

This article uses linked data from the 1995 Morocco DHS calendar and the 1992 Morocco DHS service-availability module to study the effect of service environment on contraceptive discontinuation, switching, and adoption of a modern method following a birth. The 1995 Morocco DHS also collected information on the source of supply for each episode of use of a modern method recorded in the calendar, allowing study of the association between the source of supply and discontinuation and switching rates. Multilevel event-history models are used to evaluate the impact of individual-level sociodemographic characteristics and community-level indicators of family planning service provision. The findings show that the presence of a nearby public health center is associated with higher modern-method adoption after a birth and lower method-failure rates; the presence of a pharmacy is associated with lower discontinuation due to side effects or health concerns. The degree of method-choice potential has a positive impact on both the rate of switching from the pill to another modern method and on modern-method adoption after a birth.

Variations in familial neonatal mortality risks in four countries

This paper investigates variations in the strength and structure of familial association in neonatal mortality risks in four populations; Bolivia, Kenya, Peru, and Tanzania. Exploratory analyses of the structure of the familial association are presented for each population. Random effects logistic models are then used to estimate the strength of familial association in neonatal mortality risks using a standard set of control variables. The results suggest that the strength of familial association in neonatal mortality risks is quite similar in these four populations which would be consistent with a biological explanation for the association. However, some differences were found, particularly in the form of the association in Peru, which may suggest at least a small role of other factors.

The determinants of the duration of contraceptive use in China: A multilevel multinomial discrete-hazards modeling approach

Often in demography, individuals may change state over time for a variety of reasons. Competing-risks hazards models have been developed to model such situations. This paper describes the extension of the discrete-time competing-risks hazards model to a multilevel framework that allows for data at different levels of aggregation. The model is illustrated with data from the 1988 Chinese National Survey of Fertility and Contraceptive Prevalence, which collected complete contraceptive histories. Women may stop using a method of contraception for a number of reasons; this paper describes how one can control for correlations between the outcomes of repeated spells of contraceptive use.

The determinants of the duration of contraceptive use in China: a multilevel multinomial discrete-hazards modeling approach

Often in demography, individuals may change state over time for a variety of reasons. Competing-risks hazards models have been developed to model such situations. This paper describes the extension of the discrete-time competing-risks hazards model to a multilevel framework that allows for data at different levels of aggregation. The model is illustrated with data from the 1988 Chinese National Survey of Fertility and Contraceptive Prevalence, which collected complete contraceptive histories. Women may stop using a method of contraception for a number of reasons; this paper describes how one can control for correlations between the outcomes of repeated spells of contraceptive use.

Overexpression of fetal human pigment epithelium-derived factor in Escherichia coli. A functionally active neurotrophic factor

Pigment epithelium-derived factor (PEDF) is a neurotrophic protein present in low amounts in conditioned medium of cultured fetal human retinal pigment epithelial cells. Recently, the PEDF cDNA has been cloned from a fetal human cDNA library, and its derived amino acid sequence identified it as a member of the serine protease inhibitor (serpin) supergene family (Steele, F. R., Chader, G. J., Johnson, L. V., and Tombran-Tink, J. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 1526-1530). We have prepared recombinant expression constructs from the fetal human PEDF cDNA and obtained milligram amounts of biologically active PEDF from Escherichia coli. The full-length open reading frame (Met1-Pro418) and a truncated form (Asp44-Pro418) were used in our constructs. Induction from a vector containing the truncated PEDF version, named pEV-BH, produced a protein (BH) of expected size (M(r) 42,800) associated with inclusion bodies, which contained 25-40% of expressed protein. After solubilization, BH was highly purified by gel filtration and cation exchange chromatography. The NH2-terminal sequence of the purified protein matched that of the pEV-BH construct. We have conducted neurite outgrowth assays in a human retinoblastoma Y-79 cell culture system. Recombinant PEDF (BH) demonstrated neurotrophic activity, as reported for the native PEDF. Thus, unfolded and refolded in vitro BH retained a potent biological activity. In parallel experiments, protease inhibition assays were performed. Recombinant PEDF did not have an effect on trypsin, chymotrypsin, elastase, cathepsin G, endoproteinase Lys-C, endoproteinase Glu-C, or subtilisin activity, suggesting that inhibition of known serine proteases is not the biochemical pathway for the PEDF neutrophic activity.

Rhodopsin activation causes retinal degeneration in Drosophila rdgC mutant

Drosophila rdgC (retinal degeneration-C) mutants show normal retinal morphology and photoreceptor physiology at young ages. Dark-reared rdgC flies retain this wild-type phenotype, but light-reared mutants undergo retinal degeneration. rdgC photoreceptors with low levels of rhodopsin as a result of vitamin A deprivation or a mutant rhodopsin (ninaE) gene fail to show rdgC-induced degeneration even after prolonged light treatment, demonstrating that degeneration occurs as a result of light stimulation of rhodopsin. Analysis of norpA; rdgC flies shows that the norpA-encoded phospholipase C, the target enzyme of the G protein activated by rhodopsin, is not required for rdgC-induced degeneration. Thus the rdgC+ gene product is required to prevent retinal degeneration that results from a previously unrecognized consequence of rhodopsin stimulation.