A gradient risk of cognitive impairment with vegetarian diets in older adults: highest for vegan and potential benefit for pescatarian

BACKGROUND: With global ageing accelerating, cognitive impairment has emerged as a critical public health challenge. Although vegetarian diets are often promoted for their health benefits, their specific impact on cognitive function in older adults remains scientifically controversial and insufficiently studied, particularly across diverse populations. METHODS: This multi-national study analyzed data from China, Europe and the United States. Using logistic regression and mixed-effects models, we examined graded vegetarian diets' association with cognitive impairment in older adults, adjusting for key covariates. Findings were validated through sensitivity analyses and cross-cohort verification. RESULTS: Both lacto-ovo vegetarian (28% higher risk) and vegan (33% higher risk) diets showed significantly increased cognitive impairment risk compared to omnivorous diets. A pronounced gradient effect was observed, with stricter vegetarian diets associated with greater risk. This association was particularly strong in rural populations. Validation analyses confirmed these patterns in European cohorts and showed consistent trends in U.S. CONCLUSION: Strict vegetarian diets are associated with elevated cognitive impairment risk in older adults, especially in rural areas. These findings highlight the need for careful consideration of dietary patterns in ageing populations and suggest that less restrictive vegetarian diets may be preferable for cognitive health.