Dynapenic Abdominal Obesity – Falls, Fractures, Muscle Function, and miRNA Profile

Older adults have the highest risk of falls. Dynapenia and abdominal obesity (AO) are associated with increased risk of falls and (site-specific) fractures; a cumulative risk is hypothesised in older adults with both dynapenia and AO (DAO). Aims: To identify (i) if older women with DAO have higher risk of falls and fall-related injury compared with normal weight, dynapenic, and AO, (ii) potential mechanisms (muscle size, strength, and fatigue) for increased falls risk, and (iii) whether microRNAs are implicated in the pathogenesis of DAO. In the UK Biobank, dynapenia (OR 0.86; 95%CI 0.83-0.89) and AO (1.14; 1.09-1.18) Z-scores independently associated with retrospective falls. In women with obesity, dynapenia exacerbated the risk of lower extremity fractures (2.78; 1.77, 4.37) and negated protection against other fractures (1.06; 0.82, 1.38). In the English Longitudinal Study of Ageing, older women with DAO had increased risk of prospective falls (1.5; 1.1, 2.1) related to dynapenia (1.4; 1.1, 1.7) but not AO (1.1; 0.9, 1.4). Women with AO had greater knee extensor force per unit muscle (median ± IQR; 0.347 ± 0.048 N/cm3) than normal weight women (0.270 ± 0.085) and DAO women (0.278 ± 0.170). DAO women had reduced knee flexor force per unit muscle (0.321 ± 0.131) compared to women with obesity (0.405 ± 0.107). Muscle volumes were similar between obese and DAO groups. Systematic review identified 24 miRNAs potentially associated with sarcopenic obesity. However, a panel of differentially expressed miRNAs could not be identified in women with DAO. Women with DAO have a higher risk of falls and fractures and impaired knee extensor and flexor strength which may relate to differences in muscle quality. A distinct panel of microRNAs could not be identified in women with DAO. The utility of categorising older women as DAO at an individual level requires further consideration.