Predictors of Sexual Desire and Sexual Function in Sedentary Middle-Aged Adults: The Role of Lean Mass Index and S-Klotho Plasma Levels. The FIT-AGEING Study

Abstract

BackgroundUnhealthy lifestyle and aging negatively impact sexuality; consequently, the prevalence of sexual problems increases sharply in middle-aged adults, but the determinants of low sexual desire and sexual dysfunction are not fully elucidated. AimsTo investigate the association of cardiometabolic profile, free testosterone plasma levels, body composition, physical fitness, and S-Klotho plasma levels with sexual desire and sexual function in middle-aged sedentary adults. MethodsSeventy-four (39 women) sedentary middle-aged adults (45–65 years old) were recruited for the present cross-sectional study. OutcomesThe blood samples were collected in the morning (12 h of fasting) to determine cardiometabolic biomarkers and free testosterone and S-Klotho plasma levels. The cardiometabolic risk score was calculated based on the International Diabetes Federation's clinical criteria, quantitative insulin sensitivity check index, and homeostatic model assessment of insulin resistance index. A dual-energy X-ray absorptiometry scanner was used to determine the lean mass index (LMI) and the fat mass index. Maximal oxygen uptake was determined by a maximum treadmill test using indirect calorimetry. Muscular strength was measured with knee extensor isokinetic dynamometry (60° s−1). Sexual desire was assessed with the Sexual Desire Inventory 2. Sexual function was assessed with the Massachusetts General Hospital-Sexual Functioning Questionnaire. ResultsAfter age adjustment, free testosterone plasma levels were associated with solitary sexual desire in women (R2 = 0.193, β = 0.342, P = .044). The LMI was associated with solitary sexual desire in men (R2 = 0.258, β = 0.445, P = .024) and sexual function in women (R2 = 0.470, β = −0.607, P < .001). S-Klotho plasma levels were associated with solitary sexual desire and sexual function in men (R2 = 0.412, β = 0.817, P = .001; R2 = 0.193, β = −0.659, P = .021, respectively) and with dyadic sexual desire and sexual function in women (R2 = 0.270, β = 0.508, P = .020; R2 = 0.467, β = −0.676, P < .001, respectively). Clinical ImplicationsS-Klotho plasma levels may represent a potential new biomarker for sexual desire and sexual function. Lean body mass development may benefit sexual desire and sexual function. Strengths and LimitationsStrengths include the analysis of novel and diverse biomarkers of health for sexual desire and sexual function. Limitations include the cross-sectional design and a relatively small sample size; thus, results should be interpreted cautiously and in the study population context. ConclusionS-Klotho plasma levels were strongly associated with dyadic sexual desire, solitary sexual desire, and sexual function in sedentary middle-aged adults. The LMI was also positively associated with solitary sexual desire and sexual function in men and women, respectively.Dote-Montero M, De-la-O A, Castillo MJ, et al. Predictors of Sexual Desire and Sexual Function in Sedentary Middle-Aged Adults: The Role of Lean Mass Index and S-Klotho Plasma Levels. The FIT-AGEING Study. J Sex Med 2020;17:665–677.