BACKGROUND: Previous studies have revealed how single foods or nutrients affect dementia, but the evidence for a potential link between dietary diversity and dementia is inconsistent. OBJECTIVES: This study aimed to evaluate the association between dietary diversity and the risk of incident dementia. DESIGN, SETTING AND PARTICIPANTS: This prospective study included 104,572 white participants without dementia at baseline recruited between 2006 and 2010 from the UK Biobank. MEASUREMENTS: Dietary Diversity Score (DDS) was acquired through the Oxford WebQ's 24-hour dietary recall survey spanning from 2009 to 2012. Cox proportional hazards models were used to estimate the associations between DDS, diversity scores of food groups and the risk of incident dementia. Stratified analyses were subsequently conducted to assess the potential variations across different demographic, socioeconomic, and genetic risk groups. RESULTS: Over a median follow-up period of 10.44 years, 725 participants developed incident dementia. A higher DDS was associated with a lower risk of incident dementia (HR: 0.95
95 % CI: 0.93-0.97). Stratified analyses revealed statistical significance in this association for individuals under 65 years old (HR: 0.95
95 % CI: 0.92-0.98), and those with higher polygenic risk scores (PRS
HR: 0.92
95 % CI: 0.89-0.95). Among five food groups, a higher diversity score for meat and protein alternatives was associated with a lower risk of dementia (HR: 0.92
95 % CI: 0.86-0.99). CONCLUSION: Enhancing dietary diversity reduces dementia risk, and is potentially influenced by genetic predisposition. Consuming a diverse range of foods may be an effective strategy against dementia.