Associations of dietary intake for gut microbiota with frailty risk and mortality in older adults

The associations between a diet that associated with a healthy gut microbiota and the risk of frailty, as well as mortality in older adults with frailty, remains unclear. Therefore, this study aimed to examine the associations of dietary index for gut microbiota (DI-GM) with frailty risk, as well as the all-cause mortality and cause-specific mortality in frail participants. A total of 6,104 participants aged 65 and older from six cycles of the National Health and Nutrition Examination Survey (2007–2018) were included in this study. DI-GM was calculated based on the intake of 13 dietary components, with a higher score reflecting a diet that associated with a more favorable gut microbiota profile. Frailty was assessed using the 48-item frailty index, and participants with a frailty index exceeding 0.21 were classified as having frailty. Mortality status and cause of death were determined through linkage to the National Death Index records until December 31, 2019. Weighted multivariable logistic regression was conducted to investigate the associations between DI-GM and the risk of frailty. Weighted multivariable Cox proportional hazards regression models were used to examine the associations of DI-GM with all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality in frail participants. Compared with participants in the lowest DI-GM quintile, those in the highest quintile were associated with a 32% (95% confidence interval [CI]: 14% to 46%) reduced risk of frailty. Over a median 5.3 years follow-up, 778 deaths occurred among participants with frailty, including 258 deaths due to cardiovascular disease and 139 deaths due to cancer. The hazard ratios and 95% CI for all-cause mortality, CVD mortality, and cancer mortality were 0.73 (0.57, 0.93), 0.59 (0.36, 0.97), and 1.41 (0.76, 2.62), respectively, when comparing the extreme DI-GM quintiles. DI-GM was inversely associated with the risk of frailty in older adults. Additionally, a higher DI-GM was associated with a reduced risk of all-cause mortality and CVD mortality in individuals with frailty. Diet linked to a healthy gut microbiota might be associated with a reduced risk of frailty in older adults and a decreased risk of premature mortality in individuals with frailty.