Disturbing dreams and dementia incidence across diverse cohort studies: A COSMIC collaboration study

Distressing dreams were previously reported to predict future all-cause dementia among predominantly white US participants aged 79-89 years, particularly in men. We investigated whether disturbing dreams (nightmares and bad dreams) were associated with all-cause and Alzheimer dementia (AD) among individuals aged 60-89 years from diverse international regions.

Data were from six longitudinal cohort studies across Brazil, China, France, Italy, South Korea, and Taiwan (n = 10,238, 42.5% men). Cox regressions with a random effect for study investigated associations between disturbing dreams and incident dementia, with all participants and stratified separately by sex and baseline age. Analyses examined (i) any disturbing dreams and (ii) disturbing dreams at least once a week. Fully adjusted analyses included three studies with covariates for sleep problems, medications, mental and physical health, cognition, and APOE ε4 status.

Disturbing dreams were reported by 24.2% overall and all-cause dementia, and AD incidence was 10.8 and 5.3 per 1000 person-years, respectively. In fully adjusted analyses, having any disturbing dreams was associated with increased incidence of all-cause dementia among 60-69-year-olds (hazard ratio [HR] 3.93, 95% confidence interval [CI] 1.32-11.67). There were no significant effects for older individuals. In fully adjusted sex-stratified analyses, having disturbing dreams at least once a week was associated with AD only among men (HR 3.59, 95% CI 1.44-8.96).

We found some evidence for disturbing dreams being associated with incident all-cause dementia among individuals aged 60-69 years and with AD among men. The mechanisms potentially underlying these associations remain to be clarified.