19 July 2021
Summary
García-Alfaro et al [1] published the results of a cross-sectional study that aimed at determining the impact of age, age at menopause, body mass index (BMI), and lumbar and hip bone mineral density (BMD) on muscle strength of 392 young postmenopausal women (65 or less years), with no physical disabilities and normal serum 25-hydroxyvitamin D levels (≥30 ng/ml). They analyzed variables such as age, age at menopause onset, BMI, BMD (measured with DXA scanning and expressed as lumbar and hip T-scores), and dominant hand grip strength (measured with a digital dynamometer). Mean age of the whole sample was 57.30 ± 3.69 years with a mean age at menopause onset of 50.46 ± 2.16 years and a mean BMI of 24.93 ± 3.78 k/m2. Mean DXA results were lumbar T-score of -1.16 ± 1.18 and a mean hip T-score of -0.98 ± 0.93. Mean grip force of the dominant hand was 24.10 kg, with 12.2% (48/392) of women diagnosed as having dynapenia (cut-off value of <20 kg). There was a weak but significant inverse correlation between grip strength in the dominant hand and age (r = -0.131, p = 0.009). Multivariate logistic regression analysis determined that earlier age at menopause onset (50 or less years) 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. The authors conclude that 12.2% of the studied young postmenopausal population with normal vitamin D status had dynapenia. Female age and age at menopause were significantly correlated with an increased dynapenia risk.
Commentary
During the menopausal transition and the early postmenopausal years, progressive estrogen depletion causes loss of bone mass due to an imbalance between bone resorption and bone formation. In addition, there is a reduction of muscle mass and strength and a redistribution of body fat from the periphery to the abdominal region [2,3]. There is a growing interest in recent years regarding the association of dynapenia, defined as the loss of muscle strength related to age, and BMI and nutrition. Indeed, a direct correlation has been observed between muscle strength and bone mass, that is, lower hand grip strength correlating with lower BMD, and hence higher rates of vertebral fractures [4]. Hand grip strength can be measured with a hand dynamometer, being an easy/simple and quick test to be performed in the clinical scenario, and most importantly is the fact that hand grip force correlates with leg strength. Although BMI has been used to assess nutritional status, this index is not as appropriate as DXA for the evaluation of body composition. As the authors state, although body weight is related to BMD, when body composition is analyzed with DXA, total body fat is the best predictor of bone status. Vitamin D status is another important factor correlating with muscle function, strength, balance, not to mention its role over bone status of elder women.
