Understanding the Risks of Frailty and Change in Physical Functioning in Mid- to Later-life

Abstract

Maintaining functional independence in older adults reduces the societal and individual costs of an aging population. Over the past decades, there has been a significant increase in the amount of research that focus on understanding functional independence in older adults. However, the etiology for an accelerated functional decline remains unclear. Further, a convenient public health intervention for preventing the loss of functional independence is still lacking. In this dissertation, I examine two issues related to functional change in adults: 1) the potential etiological roles of early life deprivation in the development of frailty and poor physical functioning (Chapters 2 and 3), and 2) the association of regular nut consumption with frailty risks in older adults (Chapter 4). In the first study (Chapter 2), I investigate the associations of early life factors with the risk of incident frailty in women aged 60 years old or above. I find that maternal smoking during pregnancy is associated with a higher risk of frailty after controlling for other early life variables. The adjusted hazard ratio (95% confidence interval [CI]) is 1.38 (1.28, 1.49). This association remains after additionally adjusting for adult health risk behaviors. In addition, I report that being breastfed during infancy is inversely associated with the risk of frailty. I do not find clear relations of childhood socioeconomic status (SES) and birthweight with frailty. In the second study (Chapter 3), I assess the associations of early life factors with the trajectories of physical function in mid-aged women. I identify poor childhood SES as a predictor of accelerated physical function decline in midlife. Participants in the lowest childhood SES category experience physical function decline at a rate that is approximately one third faster than their counterparts in the highest childhood SES category. This association remains, albeit slightly attenuated, after further adjustment for adult health risk behaviors. By contrast, I find that being breastfed during infancy is only modestly associated with a faster decline in physical function, whereas smaller size at birth and prenatal exposure to smoking are not related to physical function in midlife. The findings in the first two studies suggest that some aspects of functional capacity may be established even in early life. Identifying potential biological mechanisms linking early life exposures to functional change later in life may contribute to the understanding of the aging process. In the third study (Chapter 4), I investigate the associations of regular nut consumption with the risk of incident frailty in older women. I find a strong and consistent association between higher total nut consumption levels and reduced risks of frailty with a clear linear trend. Consuming 5 or more servings of nuts per week has an adjusted hazard ratio (95% CI) of 0.80 (0.75, 0.94), compared with consuming less than 1 serving of nuts per week. For individual nut types, I report a similar finding for the relations of peanut and walnut with frailty. By contrast, I do not find an association between peanut butter consumption levels and frailty. These findings suggest that nut consumption should be further tested as a convenient public health intervention for the preservation of functional independence in older adults.