Body mass index and trajectories of muscle strength and physical function over time in Mexican American older adults: Sex differences.

Background and aims: Worldwide, the prevalence of overweight and obesity has increased. We examined sex-specific patterns in the relationship of body mass index (BMI) with muscle strength and physical function among older Mexican Americans over time.

Methods and results: Participants (N = 1975) aged ≥65 years (mean = 72.4) were from a longitudinal study of Mexican American older adults (1993/94-2016). Measures collected at each interview included socio-demographics and health status; BMI (independent variable); short physical performance battery (SPPB) and handgrip strength (HGS) (outcomes). Participants were grouped into underweight (<18.5 kg/m²); normal weight (18.5-24.9 kg/m²); overweight (25-29.9 kg/m²); class I obesity (30-34.9 kg/m²); and class II/morbid obesity (≥35 kg/m²). Changes in SPPB and HGS by BMI and sex over time were estimated using general linear mixed models. Males deemed overweight (β = 0.46; Standard Error [SE] = 0.11; p-value = 0.0001), class I obesity (β = 0.43; SE = 0.15; p-value = 0.0037), and class II/morbid obesity (β = 0.66; SE = 0.29; p-value = 0.0246) scored higher in SPPB than those with normal weight. Females deemed overweight (β = 0.49; SE = 0.10; p-value = 0.0001) and class I obesity (β = 0.32; SE = 0.11; p-value = 0.0047) scored higher on the SPPB than those with normal weight. Males and females deemed overweight (β = 0.56; SE = 0.29; p-value = 0.0535 and β = 0.65; SE = 0.18; p-value = 0.0003, respectively) and class I obesity (β = 1.08; SE = 0.39; p-value = 0.0062 and β = 0.92; SE = 0.22; p-value = 0.0001, respectively) scored higher in HGS than those with normal weight.

Conclusion: We found no sex differences in the trajectories of decline for HGS and physical function. Females and males classed as overweight or class I obesity experienced slower decline in HGS and physical function.