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

The prevalence of osteoporosis differed substantially between the two cohorts studied.

• Osteoporosis prevalence was 6.3% in the English Longitudinal Study of Ageing (ELSA) cohort.
• Osteoporosis prevalence was 14.1% in the Health and Retirement Study (HRS) cohort.
• Both cohorts consisted of older adults, analyzed using generalized linear mixed models (GLMM).

Physical activity was significantly negatively associated with osteoporosis in both cohorts.

• In the ELSA cohort, physical activity was associated with reduced osteoporosis risk (OR = 0.234, P < 0.001).
• In the HRS cohort, physical activity was also associated with reduced osteoporosis risk (OR = 0.638, P = 0.028).
• The association was statistically significant in both independent longitudinal datasets.

Physical activity had a more pronounced protective effect against osteoporosis in adults aged 65 and older.

• In the subgroup aged ≥65, physical activity showed a stronger effect on osteoporosis (OR = 0.478, P < 0.001).
• Subgroup analyses accounted for age, gender, and confounding factors.
• The effect was more pronounced in older adults compared to the overall cohort estimates.

Women showed greater benefit from physical activity in terms of osteoporosis reduction compared to men.

• Subgroup analyses by gender revealed that women demonstrated greater benefit from physical activity.
• The analysis accounted for gender as a potential effect modifier.
• This finding was derived from subgroup analyses within the ELSA and HRS datasets.

Grip strength mediated a significant portion of the relationship between physical activity and osteoporosis.

• Mediation analysis in the ELSA group revealed that grip strength mediated 28.3% of the effect of physical activity on osteoporosis.
• The average causal mediation effect (ACME) was -0.007 (P < 0.001).
• This finding indicates that a meaningful part of physical activity's protective effect operates through improvements in muscle strength as measured by grip strength.
• The mediation analysis was conducted specifically in the ELSA cohort.

Physical activity, especially resistance training, reduces osteoporosis incidence by enhancing muscle strength.

• The authors specifically highlight resistance training as a particularly relevant form of physical activity for osteoporosis prevention.
• The mechanism proposed involves physical activity enhancing muscle strength, with grip strength serving as an indicator of this pathway.
• These findings were interpreted as highlighting the importance of physical activity particularly in older women for osteoporosis prevention.