Dominik Spira, Nikolaus Buchmann, Maximilian Koenig, Adrian Rosada, Elisabeth Steinhagen-Thiessen, Ilja Demuth, Kristina Norman

• Background: Sex-specific differences in factors associated with aging and lifespan, such as sarcopenia and disease development, are increasingly recognized. The study aims to assess sex-specific aspects of the association between vitamin D insufficiency and low lean mass as well as between vitamin D insufficiency and the frailty phenotype. Methods: A total of 1102 participants (51% women) from the Berlin Aging Study II were included in this cross-sectional study. Vitamin D insufficiency was defined as a 25(OH)D level <50 nmol/L. Lean mass was assessed with dual-energy x-ray absorptiometry and corrected by body mass index. Low lean mass was defined according to the Foundations for the National Institutes of Health Sarcopenia Project criteria (appendicular lean mass/body mass index <0.789 in men and <0.512 in women) and frailty defined according to the Fried criteria. Results: In a risk factor adjusted analysis, the association of vitamin D insufficiency was significantly influenced by sex (P for interaction < 0.001). Men withBackground: Sex-specific differences in factors associated with aging and lifespan, such as sarcopenia and disease development, are increasingly recognized. The study aims to assess sex-specific aspects of the association between vitamin D insufficiency and low lean mass as well as between vitamin D insufficiency and the frailty phenotype. Methods: A total of 1102 participants (51% women) from the Berlin Aging Study II were included in this cross-sectional study. Vitamin D insufficiency was defined as a 25(OH)D level <50 nmol/L. Lean mass was assessed with dual-energy x-ray absorptiometry and corrected by body mass index. Low lean mass was defined according to the Foundations for the National Institutes of Health Sarcopenia Project criteria (appendicular lean mass/body mass index <0.789 in men and <0.512 in women) and frailty defined according to the Fried criteria. Results: In a risk factor adjusted analysis, the association of vitamin D insufficiency was significantly influenced by sex (P for interaction < 0.001). Men with vitamin D insufficiency had 1.8 times higher odds of having low lean mass, with no association between vitamin D insufficiency and low lean mass in women. Participants with vitamin D insufficiency had 1.5 higher odds of being prefrail/frail with no significant effect modification by sex. Conclusions: We found notable sex-specific differences in the association of vitamin D insufficiency with low lean mass but not of vitamin D insufficiency with frailty. Vitamin D might play a relevant role in the loss of lean mass in men but not women and might be a biological marker of an unfavorable aging process associated with early development of frailty regardless of sex.…