Factors related to muscle strength in postmenopausal women aged younger than 65 years with normal vitamin D status.

Objective: The study aimed to determine the impact of age, age at menopause, body mass index (BMI), and lumbar and hip bone mineral density (BMD) on muscle strength in young postmenopausal women with normal vitamin D levels. Methods: This was a cross-sectional study performed in 392 postmenopausal women aged <65 years with normal serum 25-hydroxyvitamin D levels (≥30 ng/ml) and no physical disabilities. The following variables were recorded: age, age at menopause, BMI, BMD (measured by dual-energy X-ray absorptiometry [DXA] scanning and expressed as lumbar and hip T -scores), and dominant hand grip strength (measured with a digital dynamometer). Results are reported as mean ± standard deviation or odds ratio (OR) and 95% confidence interval (CI) as appropriate. Results: The mean age of the whole sample was 57.30 ± 3.69 years with a mean age at menopause of 50.46 ± 2.16 years and a mean BMI of 24.93 ± 3.78. Mean DXA results were lumbar T -score of -1.16 ± 1.18 and hip T -score of -0.98 ± 0.93. The mean dominant hand grip force was 24.10 kg. A total of 12.2% (48/392) of women were diagnosed with dynapenia using a cut-off value of <20 kg. A weak but significant inverse correlation was found between grip strength in the dominant hand and age ( r  = -0.131, p  = 0.009). Multivariable logistic regression analysis determined that earlier age at menopause (50 years or younger) was significantly associated with a higher risk of dynapenia (OR 2.741, 95% CI 1.23-6.11, p  = 0.014). No other significant association was found with the other variables. Conclusions: A total of 12.2% of the studied young postmenopausal women with normal vitamin D status had dynapenia. There was a weak inverse correlation between grip strength and age, and earlier age at menopause was associated with an increased dynapenia risk.