Association of Combined Healthy Lifestyle Factors With Incident Dementia in Participants With and Without Multimorbidity: A Large Population-Based Prospective Cohort Study

Background The effect of a healthy lifestyle on dementia associated with multimorbidity is not well understood. Our objective is to examine whether the adoption of a healthy lifestyle could potentially reduce the elevated risk of dementia in individuals with and without multimorbidity.Methods We utilized data from the UK Biobank cohort. A comprehensive healthy lifestyle score, ranging from 0 to 6, was generated. Cox proportional hazards models were used to examine the associations between multimorbidity, the healthy lifestyle score, and the incidence risk of dementia.Results Over a median follow-up period of 12.5 years, 5 852 all-cause dementia were recorded. Multimorbidity including cardiovascular, metabolic, neuropsychiatric, and inflammation-related diseases was associated with a higher risk of subsequent dementia. Each additional chronic disease was associated with a hazard ratio (HR) of 1.38 (95% CI: 1.33, 1.44). Compared to individuals without multimorbidity and a healthy lifestyle score of 5-6, patients with multimorbidity and a lifestyle score of 0-1 had a significantly higher risk of dementia (HR: 3.13; 95% CI: 2.64, 3.72), but the risk was markedly attenuated among those with multimorbidity and a lifestyle score of 5-6. Among patients with 3 or more diseases, the HR for dementia was 0.53 (95%CI: 0.42, 0.68) when comparing a lifestyle score of 5-6 to 0-1. And we observed more pronounced association between them among people younger than 60 years old.Conclusions Adherence to a combination of healthy lifestyle factors, especially at a young age, was associated with a significantly lower risk of dementia among participants with multimorbidity.