Digit (2D:4D) ratio is associated with muscle mass (MM) and strength (MS) in older adults: Possible effect of in utero androgen exposure

Abstract

Decline in MM and MS with aging, defined as sarcopenia, is related with physical disability, poor quality of life and death. Its mechanisms are not fully understood. Testosterone increases muscle protein synthesis. However, the effects of in utero androgen exposure to MM and MS in older adults have not been studied. In utero androgen exposure is inversely related with 2D:4D ratio. The aim of this study was to investigate the relationship between 2D:4D ratio as an indicator of in utero androgen exposure and MM and MS in elderly patients. A total of 151 older adults were included. Calf-circumference (CC) and skeletal muscle mass index (SMI) were used for the assessment of MM and hand grip strength for the assessment of MS. Mean age±SD of the patients was 73.72±6.23. Fifty-two (34.4%) of patients were male, 99 (65.6%) were female. Right and left 2D:4D were significantly and negatively correlated with hand grip strength (r=−0.365, p=0.018 and r=−0.434, p=0.005, respectively), CC (r=−0.422, p=0.002 and r=−0.459, p=0.001, respectively) and SMI (r=−0.354, p=0.018 and r=−0.348, p=0.022, respectively) in men. In women, right and left 2D:4D were significantly and negatively correlated with hand grip strength (r=−0.252, p=0.022 and r=−0.234, p=0.033, respectively), CC (r=−0.229, p=0.024 and r=−0.302, p=0.003, respectively) and SMI (r=−0.382, p<0.001 and r=−0.431, p<0.001, respectively). In this study, we found that 2D:4D ratio was significantly and negatively correlated with parameters depicting MM and MS which may suggest the possible role of in utero androgen exposure in the development of MM and MS loss in the elderly.