Combined association of dietary fibre and cognitive function with all-cause and cause-specific mortality in older adults

BACKGROUND: Dietary fibre and cognitive function are associated with the risk of mortality, respectively. Inadequate dietary fibre intake and cognitive impairment frequently co-occur in older adults, but the combined effect of dietary fibre and cognitive function on mortality remains unknown. The study was to investigate the combined effect of dietary fibre and cognitive function on mortality over a 13-year follow-up in a representative of older adults from the U.S. METHODS: We analyzed data from two cycles of the National Health and Nutrition Examination Survey (NHANES) 1999-2000 and 2001-2002 with mortality follow-up data through 13 December 2015 obtained from Public-use Linked Mortality Files. Low dietary fibre intake was defined as the lowest quartile of dietary fibre intake. Cognitive impairment was defined as below the median of Digit Symbol Substitution Test. The separate and combined effects of low dietary fibre intake and cognitive impairment on all-cause and cause-specific mortality were assessed in older adults using weighted Cox proportional hazard models adjusting for potential confounders. RESULTS: A total of 2012 participants (weighted sample was 32,765,094) aged 60 years and older were enrolled in the study. After a median follow-up of 13.4 years, 1017 participants (50.4%) were identified as all-cause deaths, including 183 (9.1%) participants dying from cancer, 199 (9.9%) participants dying from cardiovascular disease, and 635 (31.5%) participants dying from non-cancer/non-cardiovascular disease. Participants with low dietary fibre intake and cognitive impairment had nearly twice the risk of all-cause (HR, 2.030; 95% CI, 1.406-2.931) and non-cancer/non-cardiovascular (HR, 2.057; 95% CI, 1.297-3.262) mortality, and over triple cancer (HR, 3.334; 95% CI, 1.685-6.599) mortality, compared to those without both. CONCLUSIONS: The combination of low dietary fibre intake and cognitive impairment was associated with an increased risk of all-cause, cancer and non-cancer/non- cardiovascular mortality in older adults.