Relationship between Serum Vitamin D Levels and Muscle Strength in Older Adults: Results of Amirkola Elderly Cohort

Background and purpose: Population aging is a global phenomenon and increase in the number of people over 60 yeas of age proves that the world is aging. An important component of successful aging is maintaining muscle mass and its function throughout life. This study investigated the relationship between vitamin D serum level and muscle strength in the elderly as one of the important components of successful aging. Materials and methods: In this cross-sectional study, out of 1,616 people who participated in the Amirkla Elderly Cohort, 720 people were randomly selected by considering eligibility criteria. The participants were divided according to their Vitamin D serum concentrations: Vitamin D deficiency (20ng/ml>), inadequate (30ng/ml>Vitamin D>20ng/ml), and sufficient (30ng/ml<). Hand muscle strength was measured using DIGI Hand Dynamometer, and quadriceps muscle strength was measured by the MMT clinical grading system that was divided into weak and sufficient according to the standard cut-off point. SPSS V17 was used and data were analyzed using One-way ANOVA, Chi-square, and Spearman's correlation. Results: This study was conducted in 720 elderly people (360 men and 360 women) in Amirkola, north of Iran. Mean arm muscle strength was 25.84±9.8 and mean quadriceps muscle strength was 22.55±10.4. The average level of vitamin D was 35.15±33.73. There was no significant difference between the three groups in terms of arm and quadriceps muscle strength (P=0.272, P=0.370, respectively). In men, there was a positive correlation between BMI and arm muscle strength and quadriceps muscle strength (r=0.161, P=0.002 and r=0.168, P=0.0001). In women, there was a positive correlation between physical activity and arm muscle strength and quadriceps muscle strength (r=0.19, P=0.0001 and r=0.22, P=0.0001, respectively). Conclusion: This study showed no significant relationship between serum vitamin D levels and muscle strength.