Simple strategies for variance uncertainty in meta-analysis

Reliability of the measure of precision of the estimate is crucial; a correct value of the standard error of the point estimate entails that the resulting significance of the analysis is correctly stated and that confidence intervals have correct coverage probabilities. Stating an incorrect precision, on the contrary, can often result in biased and misleading results. In particular, in fixed-effects meta-analysis the overall estimator usually used in practice tends to have a variance higher than the optimal one even though this appears to be lower, just by chance. In performing a fixed-effects meta-analysis, individual estimates are weighted proportionately to the precision of the study. Such weighting is optimal only under the assumption that variances are known, which is never the case in practice. As a consequence, the estimator is sub-optimal and the resulting meta-analysis overstates the significance of the results: in particular, overstatements are dramatic when we summarise studies with small number of patients. Focusing the attention to the fixed-effects model, the main aim of this thesis is to investigate the behaviour of the precision of the overall estimator under different circumstances in order to assess how biased and incorrectly reported the overall variance of the commonly used estimator is and also to highlight in which circumstances improved estimates are deemed necessary. In fixed-effects meta-analysis, problems are related to poor estimates of the individual variances [] since these values are imprecise and both [theta] (the point estimator) and [V] (the overall variance estimator] depend upon them. Poorly estimated study variances can lead to the overall estimate of the variance of the treatment effect being badly underestimated. In order to evaluate the circumstances in which the imprecision in the estimates of [] badly affects [V], a number of simulations in different settings were performed. Under both the assumption of common and uncommon variance of the observations at the patient level, the average total number of patients per study plays an important role and this appears to be more important than the total number of each single study. Moreover, the allocation of patients per arm does not seem to be decisive for the estimated overall variance of the estimator even though balanced allocation as well as having roughly the same amount of patients per study yields better results. Furthermore, true to form, the higher the average number of patients per arm, the closer the estimator is to the optimal one, ie. the fewer the number of patients, the less precise the estimates of [] are and the greater the impact is on the results. Given the imprecision in the estimate of [], we may severely overstate the precision of [theta]. Better estimation of the variances are therefore investigated. Are there ways to account for the imprecise estimates of the within-studies variances? Shrunk variances were considered in order to assess whether borrowing information across variances would produce an overall variance estimate whose 'real' and 'average' dispersion were both closer to the optimal value. Combining measurements minimises the total 'Mean Squared Error'. Therefore, particularly when the nature of the problem is not to estimate each expected return separately but rather to minimise the total impact, shrinkage estimators represent a reasonable alternative to the classical estimators. This approach seems reasonable since the goal of this thesis is to minimise the real dispersion of the overall variance estimator. Moreover, shrinkage approaches (that combine variance information across studies and are study-specific at the same time) usually perform well under a wide range of assumptions about variance heterogeneity, behaving well both when the variances were truly constant as well as when they varied extensively from study to study. In particular, in this thesis the 'modified CHQBC estimator' suggested by Tong and Wang is used (where CHQBC stands for the James-type shrinkage estimator for variances initially proposed by Cui, Hwang, Qiu, Blades and Churchill). Results obtained via simulations (with different patterns for various variance schemes and divers average amounts of patients per study), emphasise that the estimator based on the 'shrunk variances' performs better than the one based on the estimated sample variances. Regardless of the variance structure across studies (homoscedasticity or uncommon variances), the estimator based on the shrunk variances performs optimally, even with an average small number of patients per trial, achieving almost optimal results even when the variances are strongly heterogenous and without relying on computational expensive procedures. Chapter 3 shows the results obtained if shrunk variances are used instead of the declared ones; moreover, this new approach is applied to some real data-sets showing how the declared variance tends to be higher in all cases and presumably closer the the 'real' optimal value. Finally, chapter 4 highlights the merits of this new approach to the problem of imprecise precision estimates in fixed-effects methods and also looks at the further work that needs to be done in order to improve results for this and other meta-analytical settings; this thesis, in fact, only considers the case of continuous normally distributed data ignoring binary, ordinal or survival deta meta-analyses. Moreover, despite the fact that the problem of estimating [] is particularly urgent and dramatic in the fixed-effects model, the estimation of [] might also be expected to influence random effects coverage probabilities especially when all studies in the meta-analyses are small (Brockwell and Gordon, 2001)

'Active ageing' and health: an exploration of longitudinal data for four European countries

'Active Ageing' has been promoted by the World Health Organisation (WHO) as a strategy for promoting the health and well-being of older people. Keeping active and involved in a range of activities not restricted to those associated with labour market participation may, it has been suggested, be beneficial for older people. In this research three domains of 'engagement' were considered: paid work, formal involvement (i. e. activities such as voluntary work, attendance at training courses and participation in political organisations) and informal involvement (i. e. activities such as providing care and help to family, and looking after grandchildren). Using the first two waves of the Survey of Health, Ageing and Retirement in Europe (SHARE) and the English Longitudinal Study of Ageing (ELSA), this thesis investigated both the cross-sectional association between socio-economic, demographic and health-related variables and engagement at baseline, and the longitudinal association between engagement at baseline and self-rated health (SRH) and depressive symptoms at follow-up (controlling for baseline measures of health). The analysis was based on sample members aged 50-69 at baseline in Denmark, France, Italy and England, countries selected to represent different welfare regimes. Cross-sectional findings showed that levels of engagement in paid work and formal activities varied across countries, whereas socio-economic, demographic and health related characteristics were similarly associated with engagement in all countries under study. This suggested that country-specific factors, such as retirement policies, might play an important role in determining older people's level of engagement in paid work. Cross-sectional results also suggested that work and formal engagement were associated with good health, whereas -among certain subpopulations -informal activities were associated with bad health. Longitudinal analyses showed that, in all countries, respondents in paid work at baseline were more likely to improve their SRH and less likely to become depressed than those who were `inactive'. Formal and informal engagement were not significantly associated with health at follow-up. Longitudinal results and associations found, however, might have been biased by the high rates of attrition, as multiple imputation techniques and sensitivity analyses suggested. The current research study confirms that engagement in work is an important pathway to health in late life. More attention, however, should be paid to people's working lives, the quality of work and work conditions as these may influence participation in, and withdrawal from, the labour market

The dynamics of paid and unpaid activities among people aged 50-69 in Denmark, France, Italy, and England

In the context of the current policy emphasis on extending working lives, we investigate whether the relationship between participation in paid work, other formal, and informal activities among people aged 50–69 is complementary or competitive. We also investigate differences in associations between countries using comparable longitudinal data from Denmark, France, Italy, and England. We find positive associations between informal and formal engagement in cross-sectional and longitudinal analyses. Paid work was negatively associated with formal and informal engagement, and respondents who stopped working were more likely to be engaged in formal (Denmark and France) and informal activities (England and Italy) at follow-up than respondents who continued working. However, the strongest predictor of formal and informal engagement at follow-up was baseline engagement. In the context of policy aims to extend working lives and broaden older people’s participation in other productive activities, new balances between work and other forms of engagement are still to be found

Mental health and self-rated health of older carers during the COVID-19 pandemic: evidence from England

OBJECTIVES: Older carers play a vital role supporting population health and protecting health and social care systems, yet there has been little research on understanding the effect of the pandemic on this group. In this paper, we investigate caring as a factor contributing to mental and self-rated health. METHODS: We investigate cross-sectional and longitudinal associations between provision of family care and mental health and wellbeing using longitudinal data from 5,149 members of the English Longitudinal Study of Ageing who responded to Wave 9 (2018/2019) and two COVID-19 sub-studies (June/July 2020; November/December 2020). We use logistic or linear regression models depending on outcome measures, controlling for pre-pandemic socioeconomic, demographic, and health-related variables. RESULTS: Before the pandemic, 21% of respondents cared for family or friends. Older people caring for someone inside the household mostly continued to provide care during the pandemic, with more than a quarter reporting an increase in the amount of care provided. Co-resident carers were disproportionately female, older, in the lowest wealth quintile, and more likely to report disability and chronic conditions. Both cross-sectional and longitudinal analyses suggest that, compared to those caring for people living outside the household, co-resident carers were significantly more likely to report poorer mental health and self-rated health. CONCLUSION: The health of older carers worsened disproportionately in the first year of the pandemic, a period also characterised by disruptions to support and closure of respite services. Support for carers’ mental and physical health requires greater policy attention, especially in pandemic conditions

Health Behaviors and Mental Health during the COVID-19 Pandemic: Evidence from the English Longitudinal Study of Aging

Stay-at-home and lockdown measures during the COVID-19 pandemic had an impact on health-related behaviors which in turn posed a risk to mental health, particularly among older people. In this study, we investigated how changes to health behaviors (physical activity, sleeping, eating, and drinking) impacted mental health (depression, quality of life, and life satisfaction) during and beyond the initial phase of the COVID-19 lockdown. Using data from Wave 9 (2018/19) and two COVID-19 sub-studies (June/July 2020; November/December 2020) of the English Longitudinal Study of Ageing (N = 4989), we found that health behaviors changes during lockdown were associated with poorer mental health in June/July 2020. However, in November/December 2020, higher depression, lower quality of life, and lower life satisfaction were more likely only among respondents who reported less physical activity, eating more, changes in sleep patterns, and drinking more alcohol. Public health programs should support healthy behaviors as we emerge from the pandemic

Influences on employment transitions around the birth of the first child : the experience of Italian mothers

This article studies mothers’ employment transitions around childbirth. It argues that leaving employment around childbirth and returning after an interruption might depend on multiple influences: the micro-context of individual and household characteristics, the meso-context of women’s jobs and the macro-context of broader cultural and institutional factors. This conceptual model is tested using data from the Italian Institute of Statistics (ISTAT) ‘Family and Social Subjects (2009)’ survey. The findings confirm that mothers’ transitions out of employment are shaped by micro-characteristics such as education, meso-characteristics such as status and security of prior jobs, and macro geographical and temporal factors. Subsequent returns to employment also reflect micro and macro influences, as mothers born before 1950, with low education, and large families are less likely to return; but they seem less dependent upon prior job characteristics. The research highlights the importance of considering multiple levels of influence to understand the enabling factors of maternal employment.Publisher PDFPeer reviewe

Determinants of trajectories of informal caregiving in later life: evidence from England

Although the long-term consequences of informal care provision have been well investigated, few studies have examined the trajectories of informal care provision among older people and the socioeconomic, demographic, health, and family characteristics associated with them. We use data from four waves of the English Longitudinal Study of Ageing, with 6561 respondents followed for 6 years (2012/3–2018/9). We used group-based trajectory modelling to group people's provision of care over time into a finite number of distinct trajectories of caregiving. Using multinomial logistic regressions, we then investigated the characteristics associated with these trajectories. Four distinct trajectories of caregiving were identified: “stable intensive”, “increasing intensive”, “decreasing”, and “stable no care”. Results suggest that although there are socioeconomic, demographic, and health differences across the trajectories of caregiving (with younger women in good health and poorer socioeconomic status more likely to care intensively throughout), family characteristics are their main drivers. Respondents who live alone, with no children, and no parents alive are more likely to never provide care, whereas those with older parents and who live with adults in poor health are more likely to provide stable intensive care. Also, changes in family characteristics (e.g. death of parents, widowhood, or deterioration of the partner’s health) are associated with trajectories representing increases or decreases in caregiving over time. Overall, trajectories of informal caregiving undertaken by older people are varied and these patterns are mostly associated with both the availability and health of family members, suggesting that need factors represent the most immediate reason for caregiving commitments

The impact of caring for grandchildren on the health of grandparents in Europe: a lifecourse approach

Grandparents are becoming an increasingly important source of childcare. However, caring for grandchildren may have negative health consequences particularly for grandparents with intensive commitments such as those with primary care responsibilities. To date most studies on this issue are based on cross-sectional data and do not take earlier life circumstances into account. Thus, it is not known whether (or to what extent) the relationship between grandparental childcare and health is due to cumulative advantage or disadvantage throughout the lifecourse or to the impact of grandchild care per se. Employing data from waves 1–3 of the Survey of Health, Ageing and Retirement in Europe we investigated the longitudinal relationship between grandparental childcare (i.e. intensive and non-intensive) and health once cumulative histories of advantage or disadvantage are taken into account. We used latent class analysis to categorise respondents according to childhood socio-economic and health conditions drawing on life history information. Experiences in adulthood (e.g. periods of ill health) were also captured. We created a latent continuous physical health variable based on self- and observer-measured indicators. OLS regression was used to explore the association between physical health at wave 2 and grandparental childcare at baseline, controlling for conditions in childhood and adulthood, and for health and socio-economic characteristics. We found a positive longitudinal association between grandchild care and health even after earlier life health and socio-economic conditions were taken into account. However, this significant association was found only for grandmothers, and not grandfathers. Our results suggesting the health benefits of grandchild care are important given the widespread provision of grandparental childcare in Europe. However, further research on underlying mechanisms and causal pathways between grandchild care and grandparent health, as well as on gender differences in the pattern of association, is needed

COVID-19 precautionary behaviors and vaccine acceptance among older individuals: The role of close kin

The family plays a central role in shaping health behaviors of its members through social control and support mechanisms. We investigate whether and to what extent close kin (i.e., partner and children) matter for older people in taking on precautionary behaviors (e.g., wearing a mask) and vaccination during the COVID-19 pandemic in Europe. Drawing on data from the Survey of Health, Ageing and Retirement in Europe (SHARE), we combine its Corona Surveys (June to September 2020 and June to August 2021) with pre-COVID information (October 2019 to March 2020). We find that having close kin (especially a partner) is associated with a higher probability of both adopting precautionary behaviors and accepting a COVID-19 vaccine. Results are robust to controlling for other potential drivers of precautionary behaviors and vaccine acceptance and to accounting for coresidence with kin. Our findings suggest that policymakers and practitioners may differently address kinless individuals when promoting public policy measures

Vision and Hearing Difficulties and life expectancy without ADL/IADL-limitations: Evidence from the English Longitudinal Study of Ageing and the Health and Retirement Study

BACKGROUND: Hearing and vision difficulties are some of the most common deficits experienced by older adults. Having either visual or hearing difficulty increases the risk of comorbidity, disability, and poor quality of life. So far, however, few studies have examined the association between vision and hearing difficulties on life expectancy without activities of daily living (ADL) instrumental ADL (IADL) limitations (LEWL). METHODS: Data came from the English Longitudinal Study of Ageing (ELSA) and the Health and Retirement Study (HRS) in the US from 2002 to 2013. The outcome was defined as reporting 2+ limitations with ADL/IADL. Life expectancy was estimated by discrete-time multistate life table models, for hearing and vision difficulty separately as well as for combined vision and hearing difficulties, by sex and age. RESULTS: 13% of men in England and the US had ADL/IADL-limitations, whereas for women was 16% and 19% in England and the US. At all ages, either vision or hearing difficulty was associated with shorter LEWL compared to no difficulties. Dual sensory difficulty (vision and hearing) reduced LEWL by up to 12 years in both countries. At the ages of 50 and 60 in England, hearing difficulty was associated with fewer years lived without ADL/IADL-limitations than vision difficulty. In contrast, in the US, vision difficulty led to fewer years lived without ADL/IADL-limitations than hearing difficulty. CONCLUSIONS: The implementation of strategies to reduce the prevalence and incidence of vision and hearing difficulties has the potential to increase the number of years spent without ADL/IADL-limitations