Objectives
To examine the independent association of diabetes (and its duration and severity) with quadriceps strength, quadriceps power, and gait speed in a national population of older adults.
Design
Cross-sectional nationally representative survey.
Setting
U.S.
Participants
We examined 2573 adults ≥50 years of age in the National Health and Nutrition Examination Survey 1999–2002 who had assessment of quadriceps strength.
Methods
Diabetes was ascertained by questionnaire. Measurement of isokinetic knee extensors (quadriceps) strength was performed at 60 degrees/second. Gait speed was assessed using a 20-foot walk test. Multiple linear regression analyses were used to assess the association between diabetes status and outcomes, adjusting for potential confounders or mediators.
Results
Among older U.S. adults, those with versus without diabetes had significantly slower gait speed (0.96±0.02 versus 1.08±0.01 m/s; p<0.001). After adjusting for demographics, weight, and height, diabetes was also associated with significantly lower quadriceps strength (−4.6±1.9 Newton-meters; p=0.02), quadriceps power (−4.9±2.0 Watts; p=0.02), in addition to gait speed (−0.05±0.02 m/s; p=0.002). Associations remained significant after adjusting for physical activity and C-reactive protein. After accounting for comorbidities (cardiovascular disease, peripheral neuropathy, amputation, cancer, arthritis, fracture, COPD), diabetes was only independently associated with gait speed (−0.04±0.02 m/s; p=0.02). Diabetes duration in men and women was negatively associated with age-adjusted quadriceps strength (−5.7 and −3.5 Newton-meters/decade of diabetes, respectively) and power (−6.1 and −3.8 Watts/decade of diabetes, respectively) (all p≤0.001, no significant interactions by gender). Hemoglobin A1c was not associated with outcomes accounting for body weight.
Conclusion
Compared to persons without diabetes, older U.S. adults with diabetes have lower quadriceps strength and quadriceps power that is related to the presence of comorbidities. Persons with diabetes also walk slower. Future studies should investigate the relationship of hyperglycemia with subsequent declines in leg muscle function.