Lower extremity muscular strength, sedentary behavior, and mortality

Area of Science:

• Gerontology
• Public Health
• Exercise Physiology

Background:

• Sedentary behavior is a growing public health concern, linked to increased mortality.
• Physical activity is known to mitigate mortality risks.
• The independent role of muscle strength, specifically lower extremity strength (LES), in mortality prediction requires further elucidation, especially considering varying sedentary behavior patterns.

Purpose of the Study:

• To investigate if lower extremity strength (LES) predicts all-cause mortality.
• To determine if this association is independent of physical activity levels.
• To assess the influence of different levels of sedentary behavior on the LES-mortality relationship.

Main Methods:

• Utilized data from the 1999-2002 National Health and Nutrition Examination Survey (N=2768, ages 50-85).
• Objectively measured peak isokinetic knee extensor strength.
• Self-reported physical activity and sedentary behavior; mortality assessed via National Death Index with follow-up through 2011.

Main Results:

• A 15 N increase in LES was associated with a 7% reduced risk of all-cause mortality (HR=0.93; P<0.001), even after adjusting for physical activity.
• This inverse association between LES and mortality remained consistent when sedentary behavior was included as a categorical or continuous variable.
• No statistical interaction was found between LES and sedentary behavior concerning all-cause mortality (HRinteraction=1.01; P=0.88).

Conclusions:

• Lower extremity strength is a significant independent predictor of reduced all-cause mortality in older adults.
• The protective effect of LES on mortality is not diminished by high levels of sedentary behavior.
• Maintaining or improving lower extremity strength may be a crucial strategy for longevity, irrespective of other lifestyle factors.