Flexitarian dietary patterns and neuropsychiatric multimorbidity among the oldest-old in China

Background Flexitarian dietary patterns, characterized by diets mainly based on plant foods with limited intake of animal-source foods, have attracted growing interest as a sustainable and potentially healthy eating approach. However, evidence on their associations with mental and cognitive health in the oldest-old remains limited. This study aimed to investigate the associations between flexitarian dietary patterns and neuropsychiatric outcomes among older Chinese adults. Methods Data were derived from 11,437 community-dwelling Chinese adults aged 65 years and older participating in the 2018 Chinese Longitudinal Healthy Longevity Survey. Dietary intake was assessed using a validated food frequency questionnaire, and participants were classified as omnivores or flexitarians, with flexitarians further categorized into pesco-flexitarian, ovo-lacto-flexitarian, and vegan-flexitarian subtypes. The co-occurrence of depression and cognitive impairment was defined as neuropsychiatric multimorbidity. Results After multiple imputation and adjustment for a wide range of sociodemographic, health-related, and lifestyle factors, flexitarian diets were associated with higher odds of neuropsychiatric multimorbidity compared with omnivorous diets (OR 1.42, 95% CI 1.16–1.74). Higher odds were mainly observed among pesco-flexitarians (OR 1.92, 95% CI 1.28–2.89) and vegan-flexitarians (OR 1.52, 95% CI 1.10–2.09). Flexitarian dietary patterns were also linked to increased odds of depression (OR 1.20, 95% CI 1.09–1.33) and cognitive impairment (OR 1.29, 95% CI 1.10–1.50) when examined separately, with the strongest associations seen in vegan-flexitarians. Interaction analyses indicated that the association between flexitarian diets and neuropsychiatric multimorbidity was stronger in men ( p = 0.006). These findings were consistent across multiple sensitivity analyses. Conclusion In this nationally representative sample of older Chinese adults, flexitarian dietary patterns were not associated with better neuropsychiatric health and were instead linked to higher odds of depression, cognitive impairment, and their co-occurrence. These results suggest that plant-forward diets in the oldest-old should place greater emphasis on overall dietary quality and nutrient adequacy.