[Associations of lean body mass, fat mass, and their indexes with depressive symptoms among adults aged 65 years and above in 18 longevity areas of China].

Objective: To explore the association of lean body mass (LBM), lean body mass index(LBMI), fat mass (FM) and fat mass index(FMI) with depressive symptoms in adults aged 65 and above in 18 longevity areas in China. Methods: A cross-sectional study. The study participants were from the Chinese Longitudinal Healthy Longevity Biomarker Cohort Study, comprising elderly individuals aged 65 years and above. Demographic characteristics, lifestyle factors, physical function status, and disease history were collected. Depressive symptoms were assessed using the 9-item Patient Health Questionnaire (PHQ-9). LBM and FM were measured to calculate LBMI and FMI, respectively. Participants were categorized into the depressive group and non-depressive group based on whether the PHQ-9 score≥10 points, and the differences in LBM, LBMI, FM, and FMI between the two groups were compared. Restricted cubic spline models were used to illustrate exposure-response relationships between LBM, LBMI, FM, FMI and the presence of depressive symptoms. Participants were categorized into low, moderate, and high groups based on the tertiles of LBM, LBMI, FM and FMI, respectively, and multivariable logistic regressions were applied to examine the associations of LBM, LBMI, FM, and FMI with depressive symptoms. Results: A total of 4 246 older adults were included, with 2 034 males (47.9%) and a mean age of (81.8±10.2) years. In the non-depressive group (n=4 008), the mean age was (81.9±10.2) years, with 1 957 males (48.8%). In the depressive group (n=238), the mean age was (80.8±9.6) years, with 77 males (32.4%). The LBM of the depvessive group was lower than that of the non-depressive group [(36.8±6.8) kg vs (39.0±7.5) kg, P<0.001]. Restricted cubic spline analysis indicated no non-linear exposure-response relationships between LBM, LBMI, FM, FMI, and the presence of depressive symptoms (all P>0.05). Multifactor logistic regression analysis showed that LBM and LBMI were negatively associated with the risk of depression (all P<0.05). Compared with the low LBM (or LBMI) group, the high LBM group (OR=0.458, 95%CI: 0.291-0.715) and the high LBMI group (OR=0.646, 95%CI: 0.442-0.939) had a lower likelihood of experiencing depressive symptoms. No statistically significant associations were found between FM, FMI, and depressive symptoms (all P>0.05). Conclusion: Among adults aged 65 years and above in longevity regions of China, higher LBM and LBMI are negatively associated with the risk of depressive symptoms.