Evidence of shared genetic factors in the etiology of gastrointestinal disorders and endometriosis and clinical implications for disease management.

In clinical practice, the co-existence of endometriosis and gastrointestinal symptoms is often observed. Using large-scale datasets, we report a genetic correlation between endometriosis and irritable bowel syndrome (IBS), peptic ulcer disease (PUD), gastro-esophageal reflux disease (GORD), and a combined GORD/PUD medicated (GPM) phenotype. Mendelian randomization analyses support a causal relationship between genetic predisposition to endometriosis and IBS and GPM. Identification of shared risk loci highlights biological pathways that may contribute to the pathogenesis of both diseases, including estrogen regulation and inflammation, and potential therapeutic drug targets (CCKBR; PDE4B). Higher use of IBS, GORD, and PUD medications in women with endometriosis and higher use of hormone therapies in women with IBS, GORD, and PUD, support the co-occurrence of these conditions and highlight the potential for drug repositioning and drug contraindications. Our results provide evidence of shared disease etiology and have important clinical implications for diagnostic and treatment decisions for both diseases.

Accuracy of death certifications of diabetes, dementia and cancer in Australia: a population-based cohort study.

BACKGROUND: National mortality statistics are only based on the underlying cause of death, which may considerably underestimate the effects of some chronic conditions. METHODS: The sensitivity, specificity, and positive and negative predictive values for diabetes (a common precursor to multimorbidity), dementia (a potential accelerant of death) and cancer (expected to be well-recorded) were calculated from death certificates for 9 056 women from the 1921-26 cohort of the Australian Longitudinal Study on Women's Health. Log binomial regression models were fitted to examine factors associated with the sensitivity of death certificates with these conditions as underlying or contributing causes of death. RESULTS: Among women who had a record of each of these conditions in their lifetime, the sensitivity was 12.3% (95% confidence interval, 11.0%, 13.7%), 25.2% (23.7%, 26.7%) and 57.7% (55.9%, 59.5%) for diabetes, dementia and cancer, respectively, as the underlying cause of death, and 40.9% (38.8%, 42.9%), 52.3% (50.6%, 54.0%) and 67.1% (65.4%, 68.7%), respectively, if contributing causes of death were also taken into account. In all cases specificity (> 97%) and positive predictive value (> 91%) were high, and negative predictive value ranged from 69.6% to 84.6%. Sensitivity varied with age (in different directions for different conditions) but not consistently with the other sociodemographic factors. CONCLUSIONS: Death rates associated with common conditions that occur in multimorbidity clusters in the elderly are underestimated in national mortality statistics, but would be improved if the multiple causes of death listed on a death certificate were taken into account in the statistics.

Body mass index and the diagnosis of endometriosis: Findings from a national data linkage cohort study.

BACKGROUND: Women with lower body mass index (BMI) have a higher risk of surgically confirmed endometriosis but this finding runs counterintuitive to the oestrogen-dependent theory for the disease. Increasingly, endometriosis is diagnosed via non-surgical methods. We examined BMI at age 18-23 years, and changes in BMI, and the risk of endometriosis according to the diagnostic method. METHODS: We analysed data from 11 794 young women, born in 1989-95, who completed six surveys as part of an Australian, longitudinal cohort study between 2013 and 2018. Women's survey responses were linked to administrative health records to identify endometriosis. Cox proportional hazards models modelled associations between BMI at age 18-23 years, and changes in BMI, and endometriosis. Analyses were stratified by the diagnostic method of endometriosis: clinically confirmed endometriosis (based on hospital discharge diagnosis) versus clinically suspected endometriosis (women's reports of physician-diagnosed endometriosis). RESULTS: There were 223 cases of clinically confirmed endometriosis and 396 cases of clinically suspected endometriosis. Women who gained weight after age 18-23 had lower risk of clinically confirmed endometriosis than women without endometriosis whose weight remained stable (HR = 0.64, 95% CI = 0.47-0.88). Women who were overweight (HR = 1.29, 95% CI = 1.01-1.66) at age 18-23 had higher risk of clinically suspected endometriosis than women of normal weight without endometriosis. CONCLUSIONS: The risk of clinically confirmed endometriosis was lower among women who gained weight compared to women with stable weight. The risk of clinically suspected endometriosis was higher among women who were overweight compared to normal weight.

Pre-pregnancy lifestyle characteristics and risk of miscarriage: the Australian Longitudinal Study on Women's Health.

BACKGROUND: Previous studies of lifestyle characteristics and risk of miscarriage have mostly been retrospective and failed to account for induced abortions. We examine whether pre-pregnancy body-mass index, alcohol intake and smoking influence the risk of miscarriage after accounting for induced abortions. METHODS: We conducted a prospective cohort study of 9213 women with 26,594 pregnancies participating in the Australian Longitudinal Study on Women's Health. We examined whether body-mass index, smoking and alcohol intake prior to pregnancy was associated with miscarriage. We estimated adjusted relative risks (RR) using generalized estimating equations with an exchangeable correlation matrix. We explored the impact of accounting for induced abortion by first excluding all induced abortions, and secondly including 50% of induced abortions in the comparison group. RESULTS: Of the 26,592 pregnancies which occurred during the follow-up period, 19% ended in a miscarriage. We observed an increased risk of miscarriage according to pre-pregnancy obesity compared to normal weight (adjusted RR 1.13; 95% CI 1.05, 1.21), smoking between 10 and 19 cigarettes per day compared to not smoking (adjusted RR 1.13; 95% CI 1.02, 1.25), but not smoking 20 or more cigarettes per day (adjusted RR 1.07; 95% CI 0.94, 1.21) and risky drinking (≥2 units per day; adjusted RR 1.15; 95% CI 1.03, 1.28) compared to low risk drinking (< 2 units per day). The results for smoking (adjusted RR 1.09 for 10-19 cigarettes per day; 95% CI 0.98, 1.21) was attenuated after including 50% of induced abortions in the comparison group. CONCLUSIONS: We observed a modest increased risk of miscarriage according to obesity and risky alcohol intake prior to pregnancy. There was no evidence of a dose-response relationship with smoking, and the association between smoking and risk of miscarriage was attenuated after accounting for induced abortions.

Longitudinal changes in employment following a diagnosis of endometriosis: Findings from an Australian cohort study.

PURPOSE: Endometriosis is a chronic inflammatory disease affecting the reproductive, gastrointestinal, and urinary systems. We examined changes in labor force participation amongst women with endometriosis following diagnosis. METHODS: We analyzed data from 4494 women born in 1973-78 from the Australian Longitudinal Study on Women's Health. We used multinomial logistic regression models with generalized estimating equations to examine changes in labor force participation amongst 468 women with surgically confirmed endometriosis, and 375 women with clinically suspected endometriosis, relative to a comparison group of 4151 women without endometriosis. RESULTS: At diagnosis, women with surgically confirmed endometriosis were somewhat more likely to be working part-time (OR 1.26, 95% CI 0.94-1.68) or unemployed (OR 1.46, 95% CI 0.96-2.23) than before diagnosis. After diagnosis, women with surgically confirmed endometriosis remained somewhat more likely to be working part-time (OR 1.26, 95% CI 0.88-1.80) but were significantly more likely to be unemployed (OR 1.85, 95% CI 1.16-2.96) than before diagnosis. Labor force participation for women with clinically suspected endometriosis did not differ from women without endometriosis at diagnosis and did not change over time. CONCLUSIONS: Women with surgically confirmed endometriosis transitioned out the labor force following diagnosis. Supportive workplace practices may help women remain in the labor force.

Impact of Dementia on Health Service Use in the Last 2 Years of Life for Women with Other Chronic Conditions.

OBJECTIVES: To assess the impact of dementia on the use of health and community services in the last 2 years of life by women who also had other major chronic conditions. DESIGN: Matched groups of women with a chronic condition who did or did not also have dementia, and who died or did not die for at least another 2 years. SETTING AND PARTICIPANTS: Participants in the Australian Longitudinal Study on Women's Health who were born from 1921-1926. These women were from a random, nationally representative sample of 12,432 recruited in 1996 with follow-up until 2014. METHODS: Repeated survey data and linked administrative records were used to identify women with heart disease, chronic lower respiratory tract disease, and dementia. Use of aged care services, medical visits, and hospital admissions were compared among the matched groups. RESULTS: Women with dementia were more likely to move into residential aged care, especially in the months and years before death. Consequently, they made less use of community-based services. Numbers of general practitioner visits were similar for women with or without dementia, increasing substantially in the last 4 months of life. In contrast, women with dementia were less likely to see medical specialists and slightly less likely to be admitted to hospital, even in the last 4-6 months of life when hospitalization was more common. The findings were similar whether the comorbid condition was heart disease or chronic lower respiratory tract disease. CONCLUSIONS AND IMPLICATIONS: Use of other services is affected by use of residential aged care, so the comprehensive care of people with dementia requires understanding connections between sectors.

Flexible age-period-cohort modelling illustrated using obesity prevalence data.

BACKGROUND: Use of generalized linear models with continuous, non-linear functions for age, period and cohort makes it possible to estimate these effects so they are interpretable, reliable and easily displayed graphically. To demonstrate the methods we use data on the prevalence of obesity among Australian women from two independent data sources obtained using different study designs. METHODS: We used data from two long-running nationally representative studies: seven cross-sectional Australian National Health Surveys conducted between 1995 and 2017-18, each involving 6000-8000 women; and the Australian Longitudinal Study on Women's Health which started in 1996 and involves more than 57,000 women in four age cohorts who are re-surveyed at three-yearly intervals or annually. Age-period-cohort analysis was conducted using generalized linear models with splines to describe non-linear continuous effects. RESULTS: When analysed in the same way both data sets showed similar patterns. Prevalence of obesity increased with age until late middle age and then declined; increased only slightly across surveys; but increased steadily with birth year until the 1960s and then accelerated. CONCLUSIONS: The methods illustrated here make the estimation and visualisation of age, period and cohort effects accessible and interpretable. Regardless of how the data are collected (from repeated cross-sectional surveys or longitudinal cohort studies), it is clear that younger generations of Australian women are becoming heavier at younger ages. Analyses of trends in obesity should include cohort, in addition to age and period, effects in order to focus preventive strategies appropriately.

Use of Online or Paper Surveys by Australian Women: Longitudinal Study of Users, Devices, and Cohort Retention.

BACKGROUND: There is increasing use of online surveys to improve data quality and timeliness and reduce costs. While there have been numerous cross-sectional studies comparing responses to online or paper surveys, there is little research from a longitudinal perspective. OBJECTIVE: In the context of the well-established Australian Longitudinal Study on Women's Health, we examined the patterns of responses to online or paper surveys across the first two waves of the study in which both modes were offered. We compared the following: differences between women born between 1946 and 1951 and between 1973 and 1978; types of device used for online completion; sociodemographic, behavioral, and health characteristics of women who responded online or using mailed paper surveys; and associations between mode of completion in the first survey and participation and mode of completion in the second survey. METHODS: Participants in this study, who had responded to regular mailed surveys since 1996, were offered a choice of completing surveys using paper questionnaires or Web-based electronic questionnaires starting in 2012. Two groups of women were involved: an older cohort born between 1946 and 1951 aged in their 60s and a younger cohort born between 1973 and 1978 aged in their 30s when the online surveys were first introduced. We compared women who responded online on both occasions, women who responded online at the first survey and used the paper version of the second survey, women who changed from paper to online, and those who used paper for both surveys. RESULTS: Of the 9663 women in their 60s who responded to one or both surveys, more than 50% preferred paper surveys (5290/9663, 54.74%, on the first survey and 5373/8621, 62.32%, on the second survey). If they chose the online version, most used computers. In contrast, of the 8628 women in their 30s, 56.04% (4835/8628) chose the online version at the first survey. While most favored computers to phones or tablets, many did try these alternatives on the subsequent survey. Many women who completed the survey online the first time preferred the paper version on the subsequent survey. In fact, for women in their 60s, the number who went from online to paper (1151/3851, 29.89%) exceeded the number who went from paper to online (734/5290, 13.88%). The online option was more likely to be chosen by better educated and healthier women. In both cohorts, women who completed paper surveys were more likely than online completers to become nonrespondents on the next survey. Due to the large sample size, almost all differences were statistically significant, with P<.001. CONCLUSIONS: Despite the cost-saving advantages of online compared to paper surveys, paper surveys are likely to appeal to a different population of potential respondents with different sociodemographic, behavioral, and health characteristics and greater likelihood of attrition from the study. Not offering a paper version is therefore likely to induce bias in the distribution of responses unless weighting for respondent characteristics (relative to the target population) is employed. Therefore, if mixed mode (paper or online) options are feasible, they are highly likely to produce more representative results than if only the less costly online option is offered.

Predictors of change in depressive symptoms over time: Results from the Australian Longitudinal Study on Women's Health.

BACKGROUND: Depressive symptoms fluctuate over time, and are most common amongst women in early adulthood. Understanding predictors of changes in depressive symptoms among young women may inform health promotion and early intervention. METHODS: Data were collected at three-yearly intervals from 2000 (Survey 2) to 2012 (Survey 6) from the Australian Longitudinal Study on Women's Health. The sample comprised 7663 women, aged 22-27 in 2000, who reported any indicator of poor mental health at any wave. Generalised linear mixed models identified predictors of change in depressive symptoms (CESD-10) over each three-year period. RESULTS: Depressive symptoms reduced over time. In a fully adjusted model, greater reduction in symptoms was predicted by higher initial symptoms, time, higher social support, and higher self-rated general health. Slower reduction was predicted by lower education, difficulty managing on income, high or zero alcohol consumption, stress, and history of childhood sexual assault or partner violence. Motherhood predicted an increase in depressive symptoms at Survey 2 (2000), but a decrease at Survey 5 (2009). LIMITATIONS: Although sampling was nationally representative, there is a slight bias towards Australian-born and more educated women. Further, although validated measures are used, all data are self-report. CONCLUSIONS: Fluctuations in depressive symptoms among young women are related to fixed and time-varying factors spanning multiple health and social domains. A range of factors, including education and financial resources, promotion of positive social support systems, and encouragement of health promoting lifestyles, might serve to promote young women's mental health and thus to reduce pressure on clinical services.

Mental health-related quality of life and the timing of motherhood: a 16-year longitudinal study of a national cohort of young Australian women.

PURPOSE: We examine timing of motherhood in a longitudinal cohort of young Australian women, and its relationship with mental health-related quality of life (SF-36 MHI-5), and with sociodemographic, health behaviour and health-related variables. METHODS: We analysed longitudinal self-report data from a nationally representative cohort of 10,332 Australian women born 1973-1978, surveyed 6 times between 1996 (aged 18-23) and 2012 (aged 34-39). RESULTS: Group-based trajectory modelling identified four groups. Normative Mothers (46%, mean age at motherhood 30.5 years) made the transition to motherhood close to the Australian median age. Early Mothers (25%, 25.2 years) and Very Early Mothers (7%, 20.0 years) made this transition earlier; Not Mothers (22%) had not given birth. Generalised linear mixed models showed that all groups improved mean MHI-5 scores over time. Patterns of group differences were complex: Normative and Early Mothers scored consistently highest; Very Early Mothers scored lowest at most surveys; Not Mothers' scores increased relative to others over time. Most effects disappeared after adjustment for confounders. Early and Very Early Mothers showed multiple indicators of social disadvantage, while Not Mothers had very low rates of marriage. CONCLUSIONS: Timing of motherhood is embedded in sociodemographic and personal contexts. Women with socioeconomic advantages were characterised by higher mental health-related quality of life and later transition to motherhood, but adjustment for relative advantage attenuated differences in mental health-related quality of life. The overall findings suggest a pattern of positive adaptation to circumstances, with mental health-related quality of life improving through early adulthood regardless of timing of motherhood.

Corrigendum to: Changes in smoking, drinking, overweight and physical inactivity in young Australian women 1996-2013.

Issue addressed: Smoking, risky drinking, overweight and obesity, and physical inactivity are health-risk factors (HRFs) that contribute significantly to morbidity worldwide. Several initiatives have been introduced over the past two decades to reduce these HRFs. This paper examines changes in the prevalence of HRFs in young women (aged 18-23 years) between 1996 and 2013, overall and within demographic groups.Methods: Data from two cohorts of the Australian Longitudinal Study on Women's Health, born in 1973-78 (n=14247) and 1989-95 (n=17012) were weighted to provide national estimates. Prevalence ratios were used to compare HRFs in 2013 relative to 1996.Results: In 1996, 32% were current smokers, 38% were risky drinkers, 22% were overweight or obese and 7% were physically inactive. In 2013, corresponding estimates were 19%, 35%, 33% and 6%. Between 1996 and 2013, overall smoking prevalence decreased, but remained over 43% among least educated women. Overweight and obesity increased in all demographic groups.Conclusions: The findings suggest that only smoking, which has been the subject of changes in taxation, legislation and regulation, declined significantly, in all except the least educated women. In contrast, the prevalence of overweight and obesity, which has largely been addressed through awareness campaigns and voluntary actions by the food industry, increased markedly in all demographic sub-groups.So what?: The findings show that comprehensive health promotion interventions, such as those for tobacco control, are successful (but may still be ineffective among less educated women). In contrast the measures to control population weight gain among young women have been futile so far.

Changes in smoking, drinking, overweight and physical inactivity in young Australian women 1996-2013.

Issue addressed Smoking, risky drinking, overweight and obesity, and physical inactivity are health-risk factors (HRFs) that contribute significantly to morbidity worldwide. Several initiatives have been introduced over the past two decades to reduce these HRFs. This paper examines changes in the prevalence of HRFs in young women (aged 18-23 years) between 1996 and 2013, overall and within demographic groups. Methods Data from two cohorts of the Australian Longitudinal Study on Women's Health, born in 1973-78 (n=14247) and 1989-95 (n=17012) were weighted to provide national estimates. Prevalence ratios were used to compare HRFs in 2013 relative to 1996. Results In 1996, 32% were current smokers, 38% were risky drinkers, 22% were overweight or obese and 7% were physically inactive. In 2013, corresponding estimates were 19%, 35%, 33% and 6%. Between 1996 and 2013, overall smoking prevalence decreased, but remained over 43% among least educated women. Overweight and obesity increased in all demographic groups. Conclusions The findings suggest that only smoking, which has been the subject of changes in taxation, legislation and regulation, declined significantly, in all except the least educated women. In contrast, the prevalence of overweight and obesity, which has largely been addressed through awareness campaigns and voluntary actions by the food industry, increased markedly in all demographic sub-groups. So what? The findings show that comprehensive health promotion interventions, such as those for tobacco control, are successful (but may still be ineffective among less educated women). In contrast the measures to control population weight gain among young women have been futile so far.

Cohort Profile Update: Australian Longitudinal Study on Women's Health.

In 1996 the Australian Longitudinal Study on Women's Health recruited a nationally representative sample of more than 40,000 women in three age cohorts, born in 1973-78, 1946-51 and 1921-26. At least six waves of 3-yearly surveys have been completed. Although the focus remains on factors affecting the health and well-being of women and their access to and use of health services across urban, rural and remote areas of Australia, the study has now been considerably expanded by linkage to other health data sets. For most women who have ever participated in the study, linked records are now available for: government-subsidized non-hospital services (e.g. all general practitioner visits); pharmaceutical prescriptions filled; national death index, including codes for multiple causes of death; aged care assessments and services; cancer registries; and, for most states and territories, hospital admissions and perinatal data. Additionally, a large cohort of women born in 1989-95 have been recruited. The data are available to approved collaborators, with more than 780 researchers using the data so far. Full details of the study materials and data access procedures are available at [http://www.alswh.org.au/].

Longitudinal trajectory patterns of social support: correlates and associated mental health in an Australian national cohort of young women.

PURPOSE: Although social support is a significant contributor to health and well-being, little is known about patterns of perceived social support over time in young adulthood. It is also unclear which personal characteristics are associated with different patterns, and whether there is an association between social support and mental health over time. We explore these issues in a large national cohort of young women. METHODS: We used six waves of longitudinal data spanning 16 years, from 10,369 women from the Australian Longitudinal Study on Women's Health, initially aged 18-23. We used group-based trajectory modelling to identify patterns of social support across Surveys 2-6; multinomial logistic regression to identify socio-demographic and health-behaviour predictors at Survey 1 and correlates at Survey 6 for each trajectory group; and generalised linear mixed modelling to estimate mean levels of mental health over the trajectory period for each group, adjusted for confounders. RESULTS: Four distinct trajectory groups of social support were identified: 'High' (58.5 %), 'Decreasing' (20.6 %), 'Low' (9.3 %), and 'Increasing' (11.6 %). Poor health and living outside metropolitan areas at both Surveys 1 and 6 were characteristics of women in all trajectory groups other than the 'High' group, as were early motherhood and being un-partnered at age 34-39. Other characteristics were specific to one or two trajectory groups. Patterns of mental health over time were consistent with patterns of social support. CONCLUSION: Longitudinal trajectory patterns of social support are associated with mental health, health behaviours, and demographic factors even in early adulthood.

Longitudinal analysis of relationships between social support and general health in an Australian population cohort of young women.

PURPOSE: The influence of social support on health and quality of life has been well documented. There is less evidence on whether health status affects social support, and little is known about longitudinal relationships between social support and health in early adulthood. This study investigates these associations using both concurrent and time-lagged measures at 5 time-points over 12 years during early adulthood. METHODS: A population-based cohort of 9,758 young women from the Australian Longitudinal Study on Women's Health was used. Women were aged 22-27 in 2000 and 35-39 in 2012. The General Health subscale of the SF-36 and the MOS Social Support Survey 6-item Scale were used, with scores standardised to a range of 0-100. Longitudinal tobit models were used, because both social support and general health data were left skewed, with marked ceiling effects. All models were adjusted for status of the outcome of interest at the immediately previous survey. RESULTS: With both concurrent and time-lagged measures, there was a statistically significant difference in mean general health scores across social support quintiles after adjusting for demographic and behavioural covariates: lower general health was associated with lower social support. In reverse, social support mean scores were also significantly different across general health quintiles in both concurrent and time-lagged fully adjusted models. CONCLUSION: Social support is significantly associated with both current and subsequent general health in early adulthood. The significance of the reverse associations indicates that the two mutually influence each other. This study highlights the importance of social support as a health-related quality of life issue.

Recruitment via the Internet and social networking sites: the 1989-1995 cohort of the Australian Longitudinal Study on Women's Health.

BACKGROUND: Faced with the challenge of recruiting young adults for health studies, researchers have increasingly turned to the Internet and social networking sites, such as Facebook, as part of their recruitment strategy. As yet, few large-scale studies are available that report on the characteristics and representativeness of the sample obtained from such recruitment methods. OBJECTIVE: The intent of the study was to describe the sociodemographic and health characteristics of a national sample of young Australian women recruited mainly through the Internet and social networking sites and to discuss the representativeness of their sociodemographic, health, and lifestyle characteristics relative to the population. METHODS: A cohort of 17,069 women (born between 1989 and 1995) was recruited in 2012-13 for the Australian Longitudinal Study on Women's Health. Sociodemographic characteristics (percentages, means, and 95% confidence intervals) from the online survey data were compared with women aged 18-23 years from the 2011 Australian Census. Sample data were compared by age and education level with data from the 2011-13 Australian Health Survey (AHS). RESULTS: Compared to the Australian Census data, study participants were broadly representative in terms of geographical distribution across Australia, marital status (95.62%, 16,321/17,069) were never married), and age distribution. A higher percentage had attained university (22.52%, 3844/17,069) and trade/certificate/diploma qualifications (25.94%, 4428/17,069) compared with this age group of women in the national population (9.4% and 21.7% respectively). Among study participants, 22.05% (3721/16,877) were not in paid employment with 35.18% (5931/16,857) studying 16 or more hours a week. A higher percentage of study participants rated their health in the online survey as fair or poor (rather than good, very good, or excellent) compared with those participating in face-to-face interviews in the AHS (18.77%, 3203/17,069 vs 10.1%). A higher percentage of study participants were current smokers (21.78%, 3718/17,069 vs 16.4%) and physically active (59.30%, 10,089/17,014 were classified as sufficiently active vs 48.3%) but alcohol consumption was lower (59.58%, 9865/16,558 reported drinking alcohol at least once per month vs 65.9% in the AHS). Using self-reported height and weight to determine body mass index (BMI, kg/m(2)), 34.80% (5901/16,956) of the cohort were classified as overweight or obese (BMI of 25 or more), compared with 33.6% respectively using measured height and weight in the AHS. CONCLUSIONS: Findings indicated that using the Internet and social networking sites for an online survey represent a feasible recruitment strategy for a national cohort of young women and result in a broadly representative sample of the Australian population.

Validation of the MOS Social Support Survey 6-item (MOS-SSS-6) measure with two large population-based samples of Australian women.

PURPOSE: This study aimed to validate a 6-item 1-factor global measure of social support developed from the Medical Outcomes Study Social Support Survey (MOS-SSS) for use in large epidemiological studies. METHODS: Data were obtained from two large population-based samples of participants in the Australian Longitudinal Study on Women's Health. The two cohorts were aged 53-58 and 28-33 years at data collection (N = 10,616 and 8,977, respectively). Items selected for the 6-item 1-factor measure were derived from the factor structure obtained from unpublished work using an earlier wave of data from one of these cohorts. Descriptive statistics, including polychoric correlations, were used to describe the abbreviated scale. Cronbach's alpha was used to assess internal consistency and confirmatory factor analysis to assess scale validity. Concurrent validity was assessed using correlations between the new 6-item version and established 19-item version, and other concurrent variables. RESULTS: In both cohorts, the new 6-item 1-factor measure showed strong internal consistency and scale reliability. It had excellent goodness-of-fit indices, similar to those of the established 19-item measure. Both versions correlated similarly with concurrent measures. CONCLUSION: The 6-item 1-factor MOS-SSS measures global functional social support with fewer items than the established 19-item measure.

Visualising and modelling changes in categorical variables in longitudinal studies.

BACKGROUND: Graphical techniques can provide visually compelling insights into complex data patterns. In this paper we present a type of lasagne plot showing changes in categorical variables for participants measured at regular intervals over time and propose statistical models to estimate distributions of marginal and transitional probabilities. METHODS: The plot uses stacked bars to show the distribution of categorical variables at each time interval, with different colours to depict different categories and changes in colours showing trajectories of participants over time. The models are based on nominal logistic regression which is appropriate for both ordinal and nominal categorical variables. To illustrate the plots and models we analyse data on smoking status, body mass index (BMI) and physical activity level from a longitudinal study on women's health. To estimate marginal distributions we fit survey wave as an explanatory variable whereas for transitional distributions we fit status of participants (e.g. smoking status) at previous surveys. RESULTS: For the illustrative data the marginal models showed BMI increasing, physical activity decreasing and smoking decreasing linearly over time at the population level. The plots and transition models showed smoking status to be highly predictable for individuals whereas BMI was only moderately predictable and physical activity was virtually unpredictable. Most of the predictive power was obtained from participant status at the previous survey. Predicted probabilities from the models mostly agreed with observed probabilities indicating adequate goodness-of-fit. CONCLUSIONS: The proposed form of lasagne plot provides a simple visual aid to show transitions in categorical variables over time in longitudinal studies. The suggested models complement the plot and allow formal testing and estimation of marginal and transitional distributions. These simple tools can provide valuable insights into categorical data on individuals measured at regular intervals over time.

A comparison of SF-36 summary measures of physical and mental health for women across the life course.

BACKGROUND: Physical and mental component summary scores (PCS and MCS, respectively) are often used to summarise SF-36 quality of life subscales. This paper investigates PCS and MCS across the life course and compares the trajectories obtained from two different methods of calculation. METHODS: The Australian Longitudinal Study on Women's Health is a population-based study with three cohorts of women and SF-36 surveys taken at multiple time points. Scoring coefficients for each component score were determined using factor analysis with uncorrelated (orthogonal) and correlated (oblique) rotation at the baseline survey, which were then used to compute correlated and uncorrelated PCS and MCS scores at each survey (scaled to have mean of 50 and standard deviation of 10 at baseline). RESULTS: For both methods, PCS declined progressively across the lifespan, while MCS rose in young and mid-age women to a peak and subsequently declined in later life. Differences were apparent between correlated and uncorrelated scores, most notably for MCS in the older cohort, where correlated MCS reached 54.6 but still less than uncorrelated MCS, with a random effects model indicating 1.63 (95% confidence intervals 1.58-1.67) units difference; it then declined to a score of 51.2 by the last survey and the difference widened to 3.44 (3.38-3.50) units compared with the uncorrelated MCS. CONCLUSIONS: PCS and MCS have distinct trajectories through life, with differences in results from correlated and uncorrelated component summary scores. The divergence is most notable with MCS, especially for older women, suggesting that correlated MCS and PCS should be used when examining change in health over time in this age group.