Combined Effects of Diet Quality Scores and Frailty on All-Cause Mortality and Life Expectancy in Middle-Aged and Older Adults

<b>Background:</b> Frailty is known to elevate the risk of all-cause mortality and shorten life expectancy. Although the effects of diet on health are well documented, the specific interaction between diet quality and frailty remains unexplored. This research aims to examine the combined effects of various diet quality scores and frailty on all-cause mortality and life expectancy among middle-aged and older adults. <b>Methods:</b> A total of 151,628 participants were sourced from the UK Biobank for analysis. Frailty phenotype (FP) and frailty index (FI), as two different approaches, were used to assess frailty status. Diet quality was evaluated through seven diet quality scores: the Alternate Healthy Eating Index (AHEI), Dietary Approaches to Stop Hypertension (DASH) score, Mediterranean diet (MED) score, Dietary Inflammatory Index (DII), and three plant-based diet indices (overall PDI, healthful PDI, and unhealthful PDI). Cox proportional hazards models were applied to calculate adjusted hazard ratios (HRs) for overall mortality and predict life expectancy differences. <b>Results:</b> Over a median follow-up period of 12.2 years, 8231 deaths were identified. After accounting for potential confounding factors, frail individuals in the unhealthier tertile of diet scores exhibited markedly elevated mortality risks, ranging from 1.99 to 2.07 based on the frailty index and 2.79 to 3.06 based on the frailty phenotype, compared to their robust counterparts in the healthier tertile. Regardless of frailty categories, a healthier diet was associated with longer life expectancy and with lower mortality risk in a dose-response relationship. <b>Conclusions:</b> The healthier tertile of diet scores was found to mitigate the detrimental effects of frailty, emphasizing diet quality as a modifiable factor in promoting healthier aging. Evidence suggests that it is never too late to adopt healthier dietary habits for significant health benefits.