Association of blood selenium levels with frailty in the older adults aged 65 years and above in nine longevity areas of China

Objective To explore the relationship between blood selenium levels and the risk of prevalent frailty in old adults aged 65 years and above in longevity areas of China.

Methods The data were obtained from the 2017-2018 cross-sectional study of the Healthy Aging and Biomarkers Cohort Study. A total of 2 464 older adults aged 65 years and above were included from 9 longevity areas of China. A questionnaire survey was conducted to investigate the demographic variables, life style, eating habits, health status and other information. The frailty index was used to assess the degree of frailty of the participants. The fasting venous blood was collected and measured by ICP-MS to obtain the internal exposure level of selenium. According to the quartiles of blood selenium levels, the participants were divided into 4 groups (Q₁-Q₄). A multivariate logistic regression model was used to analyze the relationship between blood selenium and frailty, and the restricted cubic spline was used to investigate the exposure-response relationship between blood selenium and frailty.

Results The 2 464 participants were aged 84.55±11.38 years, with 1 180(47.89%) males and 1 284(52.11%) females, of whom 1 866(75.73%) were non-frail and 598 (24.27%) were frail. The geometric mean blood selenium levels of men and women were 109.73 μg/L and 108.33 μg/L, respectively; the geometric mean blood selenium levels of older adults aged 65-79, 80-89, 90-99, and ≥ 100 were 119.15, 106.54, 102.12, and 98.04 μg/L, respectively. After adjusting the confounding factors using a multivariate logistic regression model, the results showed that compared with the older adults in the Q₁ group, those in the Q₂, Q₃, and Q₄ groups with higher blood selenium concentrations had lower odds of prevalent frailty (odds ratios were 0.68, 0.65, and 0.59, respectively, 95% CI: 0.49-0.96, 0.46-0.92, and 0.40-0.87, respectively). The restricted cubic spline model showed that there was a nonlinear exposure-response relationship between blood selenium concentration and the risk of prevalent frailty in the older adults aged 65 and above (P_nonlinearity < 0.01).

Conclusion There is a negative association between blood selenium levels and the risk of prevalent frailty in the older adults aged 65 and above in 9 longevity areas of China.