The associations of dietary fibre and fibre-rich foods with the prevalence and incidence of neuropsychological health outcomes in older adults

Neuropsychological disorders, including anxiety, depression, and dementia, are significant public health problems among older adults. While psychotropics are effective treatments, long-term treatment often has adverse side effects (1) . Many patients often seek healthy food consumption as an alternative preventive strategy. Dietary fibre has been suggested for many health benefits, including cardiometabolic health and anti-inflammation, which may influence neurological health through the gut-brain axis (2) . However, fibre’s role in neuropsychological health outcomes in older people is unclear. This study examined the potential role of dietary fibre intake and consumption of fibre-rich foods in neurological health outcomes in older Australians. We utilised data from the Ageing Study (MAS) of 1,037 participants aged 70–90 (3) . At baseline, dietary fibre, whole grains, fresh fruit, vegetables, and nuts and legumes consumption was estimated using the Cancer Council of Victoria food frequency questionnaire. The intake amount was further derived into tertiles (T), with T1 in the lower 33rd%tile and T3 in the upper 33rd%tile. Depressive symptoms (Geriatric Depression Scale), anxiety symptoms (Goldberg Anxiety Scale), and psychological distress (Kessler Psychological Distress Scale) were assessed. Linear regression models were used to estimate beta coefficients for the associations cross-sectionally. Incident dementia was defined using diagnostic criteria, clinical assessments, and a consensus panel review. Nine hundred and sixty-three participants were followed up from the baseline (2005) until wave 4 (2011) [median: 5.8 (IQR: 3.1–5.9) years; 97 incident cases). Incident depression was defined as diagnoses by healthcare professionals and treatments for depression. Eight hundred and nine participants were followed up from the baseline (2005) until wave 3 (2009) [median: 3.9 (IQR: 1.9–4.0) years; 109 incident cases). Cox proportional hazard models were used to estimate hazard ratios (95% CIs). All models were adjusted for demographic characteristics, lifestyle factors, and health history. Among 963 participants (mean age: 78.5; 5.8% females) in the cross-sectional analysis, compared with T1, higher vegetable intake was associated with fewer depressive symptoms (T2: β = 0.52; T3: β= −0.53; both p < 0.05), psychological distress (T2: β = −0.59; T3: β = −1.13; both p < 0.05), and anxiety symptoms (T3: β = −0.37; p = 0.03). Combined intake of vegetables and fruit was inversely associated with fewer psychological distress symptoms (T2: β = −0.55; p = 0.06; T3: β = −1.3; p < 0.05). In the highest tertile, dietary fibre was associated with fewer depressive symptoms (T3: β = −0.47; p = 0.04). In the longitudinal analysis, dietary fibre intake was associated with a 43–56% lower risk of incident dementia (T2 vs T1: adj.HR = 0.57; 95% CI: 0.31–1.03; T3 vs T1: adj.HR = 0.44; 95% CI: 0.19–1.01). Intakes of whole grains, fruit, nuts and legumes were not associated with the outcomes assessed. In a cohort of older Australians, dietary fibre intake appeared to be protective in reducing depressive symptoms cross-sectionally and the risk of incident dementia longitudinally. Additionally, vegetable consumption was associated with fewer symptoms related to depression, anxiety, and distress cross-sectionally.