In their post-hoc analysis of the Study of Women’s Health Across the Nation (SWAN) , Woods et al. assessed the relationship between lean body mass (LBM) and vasomotor symptoms (VMS) in 2,533 women aged 42–52 years, based on follow-up data over a 10-year period. Cross-sectionally, the presence of any VMS (hot flashes or night sweats) was negatively associated with baseline LBM (adjusted odds ratio, 0.93; 95% confidence interval, 0.87–0.99; p = 0.036). Longitudinally, they were negatively associated with the percent change in LBM from baseline (0.12 [0.04–0.33], p < 0.001) and from a prior visit (0.17 [0.06–0.49], p < 0.003), adjusted for concurrent LBM. The estimated probability of developing VMS decreased significantly as LBM increased (from 71% in women with skeletal mass index [SMI] of 4 to 37% in those with SMI of 14). These results suggest that maintaining muscle mass through resistance training may protect against the development of VMS in women transitioning through menopause.
Sarcopenia, defined as an age-related loss in muscle mass and strength, is associated with functional impairment (with limitations in mobility performance such as walking and climbing stairs) and physical disability (difficulty in performing activities of daily living) . Its prevalence has been reported to increase from 37% in women in their 40s to 57% in those in their 50s, suggesting a link between menopause and the pathogenesis of this disease . Although sarcopenia is regarded as one of the most critical health problems in the elderly, recent studies have revealed that muscle mass also plays an important role in improving the quality of life in younger women.
Berin et al. assigned 65 Swedish postmenopausal women with moderate to severe VMS to either resistance training (e.g., chest press, leg press, seated row, and leg curls) or unchanged physical activity. After 15 weeks, they found that working out three times per week significantly reduced VMS frequency (-43.6% vs. -2.0%) . This is not in line with previous studies that showed no or only modest effects of exercise on VMS, which could be explained by the difference between aerobic and resistance exercise in terms of induction of central β-endorphin. A known stabilizer of thermoregulation released during exercise, this opioid neuropeptide is known to decrease in concentration in the cerebrospinal fluid after menopause, which could partly contribute to the pathogenesis of menopausal VMS.
In their recent analysis of SWAN data, enrolling more than 2,500 middle-aged women, Woods et al. showed that the presence of any VMS (hot flashes or night sweats) was negatively associated, both cross-sectionally and longitudinally, with LBM represented by SMI measured with a bioelectrical impedance analyzer. This suggests that women with higher muscle mass are at lower risk of being bothered by VMS, and those who maintain muscle mass are less likely to develop symptoms as they transition through menopause . The former supports the recent finding by Zhou et al. that the lean trunk mass is negatively associated with moderate to severe menopausal symptoms , and the latter was reported for the first time in the present paper. The authors speculated that loss of muscle mass induced by estrogen deficiency diminishes protection against oxidative stress, leading to VMS development.
The study adds to the existing literature that has proved the beneficial role of exercise, either aerobic or resistance, to women’s well-being during their middle age and beyond. To corroborate the current finding, randomized controlled trials evaluating the effects of resistance training on VMS are warranted. These could help acquire more information to determine which is more important to reduce the symptoms, exercise per se or maintenance of muscle mass.
Professor, Department of Women’s Health, Tokyo Medical and Dental University, Tokyo, Japan
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