Adolescent childbirth and mobility disability among women ages 15-49: an analysis of population health surveys from 14 low-income and middle-income countries

Pregnancy is linked to faster epigenetic aging in young women

A central prediction of evolutionary theory is that energy invested into reproduction comes at the expense of somatic maintenance and repair, accelerating biological aging. Supporting this prediction are findings that high fertility among women predicts shorter lifespan and poorer health later in life. However, biological aging is thought to begin before age-related health declines, limiting the applicability of morbidity and mortality for studying the aging process earlier in life. Here, we examine the relationship between reproductive history and biological aging in a sample of young (20 to 22yo) men and women from the Cebu Longitudinal Health and Nutrition Survey, located in the Philippines (n = 1,735). We quantify biological aging using six measures, collectively known as epigenetic clocks, reflecting various facets of cellular aging, health, and mortality risk. In a subset of women, we test whether longitudinal changes in gravidity between young and early-middle adulthood (25 to 31yo) are associated with changes in epigenetic aging during that time. Cross-sectionally, gravidity was associated with all six measures of accelerated epigenetic aging in women (n = 825). Furthermore, longitudinal increases in gravidity were linked to accelerated epigenetic aging in two epigenetic clocks (n = 331). In contrast, the number of pregnancies a man reported fathering was not associated with epigenetic aging among same-aged cohort men (n = 910). These effects were robust to socioecological, environmental, and immunological factors, consistent with the hypothesis that pregnancy accelerates biological aging and that these effects can be detected in young women in a high-fertility context.

The contributions of fertility during adolescence to disability across the life-course: hypothesized causal pathways, research gaps, and future directions

CONTEXT

Robust associations have been identified between fertility during adolescence and the disablement process, including pathologies, impairments, functional limitations and disability. Limited theoretical or empirical research considers how and why such relationships exist generally or with the individual associated components of disablement.

OBJECTIVE

To consolidate and critically evaluate literature to describe testable, theory-based hypotheses to guide future research on the mechanisms by which fertility during adolescence contributes to disablement.

METHODS

Targeted literature review of research from diverse global settings contextualised in two well-accepted theoretical frameworks in life-course epidemiology: the cumulative risk model and the critical period approach.

RESULTS

Five hypothesised causal pathways linking adolescent fertility to disablement in later life are described: 1) Causal relationship initiated by fertility during adolescence; 2) Common cause(s) for both, such as adverse childhood experiences; 3) Contributing cause(s) to adolescent fertility; 4) Interaction between adolescent fertility and other risk factors; and 5) Critical period effects unique to adolescence. Most research on the topic is on pathologies versus functional limitations and disability.

CONCLUSION

We highlight promising research avenues to inform future research and interventions on adolescent fertility and the disablement process. This work provides theoretical clarity, identifies research gaps, and offers hypotheses-testing opportunities for future research.