Heterogeneity of Frailty Trajectories and Associated Factors in the Lothian Birth Cohort 1936

<b><i>Introduction:</i></b> Recent research suggests that the experience of frailty progression may be heterogeneous, with latent subpopulations of older adults following distinct trajectories of frailty. We aimed to investigate this notion and determine whether certain factors are associated with the membership of these subpopulations. <b><i>Methods:</i></b> Data from 5 data waves collected over 12 years in participants of the Lothian Birth Cohort 1936, aged 70 at baseline, were used to derive the frailty index (FI) (NW1 = 1,091, NW5 = 431). These were used in latent class mixed modelling to estimate subpopulations of frailty trajectories. <b><i>Results:</i></b> A quadratic latent class mixed model found 3 distinct groupings, which followed a low (61%, <i>n</i> = 632), medium (36%, <i>n</i> = 368), or high (3%, <i>n</i> = 28) FI trajectory. Each grouping had different intercepts and slopes, with the high grouping following the steepest trajectory indicating a rapid increase in frailty. Findings showed that in general, those in the low grouping were younger, had higher education, higher age 11 cognitive ability, and were from a higher social class than those in the medium and high groupings. <b><i>Discussion/Conclusion:</i></b> Our findings demonstrate heterogeneity in frailty trajectories over 12 years in individuals aged 70 years at baseline. Membership of higher frailty trajectory groupings was associated with lower social class, less education, and lower childhood cognitive ability, indicating the potential for future interventions to target individuals who are at the greatest risk of belonging to the high frailty trajectory. Future research is required to continue this line of inquiry by exploring other risk and protective factors, and importantly, to assess whether it is possible to realign an individual’s membership to a less detrimental grouping of frailty trajectory.

Influence of childhood socioeconomic position and ability on mid-life cognitive function: evidence from three British birth cohorts

BackgroundChildhood socioeconomic position (SEP) is robustly associated with cognitive function later in life. However, it is unclear whether this reflects a direct relationship, or an indirect association via modifiable factors such as educational attainment and occupation. We sought to clarify these associations using retrospectively harmonised data from three ongoing British birth cohorts.MethodsWe analysed data from the 1946 National Survey of Health and Development (n=2283), the 1958 National Child Development Study (n=9385) and the 1970 British Cohort Study (n=7631). Retrospective harmonisation was used to derive equivalent indicators of cognition, SEP, education and occupation across the three cohorts. Structural equation modelling was used to examine the association between childhood SEP and mid-life cognitive function, via childhood cognitive ability, educational attainment and mid-life occupation.ResultsAcross all three cohorts, no direct pathways were observed between childhood SEP and mid-life cognitive function. Rather, this association was indirect via the three temporally ordered mediators. In addition, the direct pathway between childhood cognition and adult cognitive function was weaker in the two younger studies.ConclusionsAcross three British birth cohorts, we found that the association between early life SEP and mid-life cognitive function was fully mediated by childhood cognitive ability, educational attainment and occupational status. Furthermore, the association between early cognitive ability and mid-life cognitive function has decreased in younger generations. Therefore, cognitive function in adulthood may be influenced by modifiable factors and societal change.

Do childhood socioeconomic circumstances moderate the association between childhood cognitive ability and all-cause mortality across the life course? Prospective observational study of the 36-day sample of the Scottish Mental Survey 1947

BackgroundThere is growing evidence that higher childhood cognitive ability predicts lower all-cause mortality risk across the life course. Whereas this association does not appear to be mediated by childhood socioeconomic circumstances, it is unclear whether socioeconomic circumstances moderate this association.MethodsThe moderating role of childhood socioeconomic circumstances was assessed in 5318 members of the 36-day sample of the Scottish Mental Survey 1947. Univariate, sex-adjusted and age-adjusted, and mutually adjusted Cox models predicting all-cause mortality risk up to age 79 years were created using childhood IQ scores and childhood social class as predictors. Moderation was assessed by adding an interaction term between IQ scores and social class and comparing model fit.ResultsAn SD advantage in childhood IQ scores (HR=0.83, 95% CI 0.79 to 0.86, p<0.001) and a single-class advantage in childhood social class (HR=0.92, 95% CI 0.88 to 0.97, p<0.001) independently predicted lower mortality risk. Adding the IQ–social class interaction effect did not improve model fit (χ2Δ=1.36, p=0.24), and the interaction effect did not predict mortality risk (HR=1.03, 95% CI 0.98 to 1.07, p=0.25).ConclusionsThe present study demonstrated that the association between higher childhood cognitive ability and lower all-cause mortality risk is not conditional on childhood social class. Whereas other measures of socioeconomic circumstances may play a moderating role, these findings suggest that the benefits of higher childhood cognitive ability for longevity apply regardless of the material socioeconomic circumstances experienced in childhood.

A Meta-Analysis of Stressors from the Total Environment Associated with Children’s General Cognitive Ability

General cognitive ability, often referred to as ‘general intelligence’, comprises a variety of correlated abilities. Childhood general cognitive ability is a well-studied area of research and can be used to predict social outcomes and perceived success. Early life stage (e.g., prenatal, postnatal, toddler) exposures to stressors (i.e., chemical and non-chemical stressors from the total (built, natural, social) environment) can impact the development of childhood cognitive ability. Building from our systematic scoping review (Ruiz et al., 2016), we conducted a meta-analysis to evaluate more than 100 stressors related to cognitive development. Our meta-analysis identified 23 stressors with a significant increase in their likelihood to influence childhood cognitive ability by 10% or more, and 80 stressors were observed to have a statistically significant effect on cognitive ability. Stressors most impactful to cognition during the prenatal period were related to maternal health and the mother’s ability to access information relevant to a healthy pregnancy (e.g., diet, lifestyle). Stressors most impactful to cognition during the early childhood period were dietary nutrients (infancy), quality of social interaction (toddler), and exposure to toxic substances (throughout early childhood). In conducting this analysis, we examined the relative impact of real-world exposures on cognitive development to attempt to understand the inter-relationships between exposures to both chemical and non-chemical stressors and early developmental life stages. Our findings suggest that the stressors observed to be the most influential to childhood cognitive ability are not permanent and can be broadly categorized as activities/behaviors which can be modified to improve childhood cognition. This meta-analysis supports the idea that there are complex relationships between a child’s total environment and early cognitive development.

Early-life circumstances and the risk of function-limiting long-term conditions in later life

Older adults are particularly prone to function-limiting health issues that adversely affect their well-being. Previous work has identified factors from across the life course –childhood socio-economic status, childhood cognitive ability and education – that predict later-life functional outcomes. However, the independence of these contributions is unclear as later-in-the-life-course predictors are themselves affected by earlier ones. The present study capitalised on the recent linkage of the Scottish Mental Survey 1947 with the Scottish Longitudinal Study, using path analyses to examine the direct and indirect associations between life-course predictors and the risk of functional limitation at ages 55 (N = 2,374), 65 (N = 1,971) and 75 (N = 1,534). The odds of reporting a function-limiting long-term condition increased across later life. At age 55, reporting a functional limitation was significantly less likely in those with higher childhood socio-economic status, higher childhood cognitive ability and higher educational attainment; these associations were only partly mediated by other predictors. At age 65, adult socio-economic status emerged as a mediator of several associations, although direct associations with childhood socio-economic status and childhood cognitive ability were still observed. At age 75, only childhood socio-economic status and adult socio-economic status directly predicted the risk of a functional limitation, particularly those associated with disease or illness. A consistent pattern and direction of associations was observed with self-rated health more generally. These results demonstrate that early-life and adult circumstances are associated with functional limitations later in life, but that these associations are partly a product of complex mediation between life-course factors.

Childhood socio-economic circumstances, cognitive function and education and later-life economic activity: linking the Scottish Mental Survey 1947 to administrative data

As the population ages, older adults are expected to work for longer into the life course. However, older adults experience particular problems staying economically active, even prior to reaching statutory retirement. Recent work has suggested that economic activity in midlife can be predicted by the far-reaching effects of early life, such as childhood socio-economic circumstances, cognitive ability and education. The present study investigates whether these same early-life factors predict the odds of being economically active much later in life, from age 55 to age 75. We capitalise on data linkage conducted between a subsample of the Scottish Mental Survey 1947 cohort and the Scottish Longitudinal Study, which includes three waves of national census data (1991, 2001 and 2011). The structural association between early-life factors and later-life economic activity was assessed using latent growth curve analyses conducted for males and females separately. In both males and females, the odds of being economically active decreased non-linearly across the 20-year follow-up period. For males, greater odds of being economically active at age 55 were predicted by higher childhood cognitive ability and higher educational attainment. For females, greater odds of being economically active at age 55 were predicted by higher childhood socio-economic status and higher childhood cognitive ability. In contrast, early-life factors did not predict the odds of becoming inactive over the 20-year follow-up period. We suggest that early-life advantage may contribute to the capacity for work in later life, but that it does not necessarily protect from subsequent decline in this capacity.