Life course socioeconomic adversity and its implications for musculoskeletal ageing

Yusuf, Mohammed A. (2023) Life course socioeconomic adversity and its implications for musculoskeletal ageing. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Developing good musculoskeletal health and function into mid-adulthood, and maintaining it into later adulthood, can help people live independent and healthy lives, with grip strength and standing balance performance serving as important markers. However, associations between life course socioeconomic position (SEP) and these markers remain unclear. The literature on the associations between life course SEP, grip strength, and standing balance performance has gaps and limitations, such as inconsistent patterns of associations at younger ages, insufficient evidence on underlying pathways, a scarcity of studies using prospectively ascertained SEP indicators, and a lack of examination of ethnic differences where feasible. To address these limitations, the body of work set out in this thesis took a life course epidemiological perspective to examine the associations of SEP across life with grip strength and standing balance performance, utilising data from the 1970 British Cohort Study (BCS70) and the UK Biobank (UKB). In women, lower SEP in childhood and adulthood were robustly associated with weaker grip strength at age 46 years in the BCS70, and lower adulthood SEP was associated with weaker grip strength between ages 37 and 69 in UKB. In men, there were no associations between indicators of childhood SEP and grip strength at age 46 years in the BCS70, but lower adulthood SEP was linked to stronger grip strength in both BCS70 and UKB, possibly due to higher levels of occupational activity related to manual occupations among middle-aged men. Associations between adulthood SEP and grip strength varied by age and ethnicity in men, with men of South Asian heritage not experiencing the same occupational activity advantage as men of other ethnic groups. Additionally, in the UKB, South Asian men were generally weaker than White men, while Black men and women were stronger than their White counterparts, independent of height, adiposity, and health and behavioural factors. Lower childhood SEP was associated with poorer balance performance at age 46 years in the BCS70, primarily explained by adulthood SEP. The association of lower adulthood SEP with poorer standing balance performance was largely unexplained by the potential mediators examined. These findings have relevance for interventions aimed at improving strength and balance outcomes and promoting healthy ageing. Such interventions should encompass policy measures to address socioeconomic inequalities across the lifespan and ethnic differences in adulthood, along with targeted messaging for strength and balance training.