# Grip strength as a mediator in the relationship between physical activity and osteoporosis in older adults: Evidence from two longitudinal cohort studies

## TL;DR

Physical activity reduces osteoporosis risk in older adults, partly by improving grip strength, especially in women.

## Contribution

This study identifies grip strength as a key mediator linking physical activity to reduced osteoporosis risk in older adults.

## Key findings

- Physical activity significantly reduces osteoporosis risk in both ELSA and HRS cohorts.
- Grip strength mediates 28.3% of the protective effect of physical activity against osteoporosis.
- Older women benefit more from physical activity in reducing osteoporosis risk.

## Abstract

Osteoporosis is a skeletal disorder characterized by reduced bone mass and increased fracture risk. With the aging global population, its prevalence is rising, posing a significant public health challenge. Physical activity is considered an effective intervention to reduce osteoporosis risk, but the role of grip strength as a mediator remains underexplored.

Data from the English Longitudinal Study of Ageing (ELSA) and the Health and Retirement Study (HRS) were analyzed using generalized linear mixed models (GLMM) and mediation analysis to explore the impact of physical activity on osteoporosis and the role of grip strength. Subgroup analyses accounted for age, gender, and confounding factors.

The prevalence of osteoporosis was 6.3% in ELSA and 14.1% in HRS. A significant negative correlation was found between physical activity and osteoporosis in both groups (ELSA: OR = 0.234, P < 0.001; HRS: OR = 0.638, P = 0.028). In those aged ≥65, physical activity had a more pronounced effect (OR = 0.478, P < 0.001). Women showed greater benefit. Mediation analysis in the ELSA group revealed that grip strength mediated 28.3% of the effect of physical activity on osteoporosis (ACME = −0.007, P < 0.001).

Physical activity, especially resistance training, reduces osteoporosis incidence by enhancing muscle strength, with grip strength playing a mediating role. These findings highlight the importance of physical activity, particularly in older women, for osteoporosis prevention.