Changes and major determinants of relative muscle power loss in older adults: results from an 8-year longitudinal study.

OBJECTIVES

This study aimed to evaluate longitudinal changes in relative sit-to-stand power (STSpower) in older adults and investigate contributing factors to its decline.

METHODS

565 older adults (143 men and 422 women; ≥ 65 years) were tested at baseline and after 8 years of follow-up. Relative STSpower was estimated from the 30-s STS test using the Alcazar equation while body composition was assessed using bioelectrical impedance analysis. The basic components of relative STSpower (specific STSpower, leg muscle mass, body fat mass and fat-free mass) were calculated. Factors such as medication intake and daily walking and sitting time were recorded.

RESULTS

Relative STSpower declined significantly in both sexes, with greater reductions in men than women (11.8 vs 8.0%, p = 0.024). Losses were greater in men and women aged ≥75 years (- 2.0% and - 2.0%∙year-1, respectively) compared to those aged 65-69 years (- 1.1% and - 0.7% year-1, respectively). Approximately 95% of the average decline in relative STSpower was attributed to reductions in specific STSpower, while the remaining 5% was explained by the loss of leg muscle mass. Medication intake was associated with an increased risk of decreasing power in women (OR = 1.87, p = 0.049), while a trend was shown in men (OR = 2.58; p = 0.052). Sedentary time showed a tendency only in women (OR = 1.73; p = 0.085).

CONCLUSION

Relative STSpower decreased progressively with aging, but differently in older men and women. This decline was primarily driven by reductions in specific STSpower, while the loss in leg muscle mass contributed to a lesser extent. Medication and sedentary time may influence power loss.