OBJECTIVE: High neuroticism has been associated with a greater risk of dementia, 
and an active/socially integrated lifestyle with a lower risk of dementia. The 
aim of the current study was to explore the separate and combined effects of 
neuroticism and extraversion on the risk of dementia, and to examine whether 
lifestyle factors may modify this association.
METHODS: A population-based cohort of 506 older people with no dementia from the 
Kungsholmen Project, Stockholm, Sweden, was followed up for an average of 6 
years. Personality traits were assessed using the Eysenck Personality Inventory. 
Dementia was diagnosed by specialists according to DSM-III-R criteria.
RESULTS: Neither high neuroticism nor low extraversion alone was related to 
significantly higher incidence of dementia. However, among people with an 
inactive or socially isolated lifestyle, low neuroticism was associated with a 
decreased dementia risk (hazard ratio [HR] = 0.51, 95% confidence interval [CI] 
= 0.27-0.96). When compared to persons with high neuroticism and high 
extraversion, a decreased risk of dementia was detected in individuals with low 
neuroticism and high extraversion (HR = 0.51, 95% CI = 0.28-0.94), but not among 
persons with low neuroticism and low extraversion (HR = 0.95, 95% CI = 
0.57-1.60), nor high neuroticism and low extraversion (HR = 0.97 95% CI = 
0.57-1.65). Stratified analysis by lifestyle showed that the inverse association 
of low neuroticism and high extraversion in combination was present only among 
the inactive or socially isolated persons.
CONCLUSION: Low neuroticism in combination with high extraversion is the 
personality trait associated with the lowest dementia risk; however, among 
socially isolated individuals even low neuroticism alone seems to decrease 
dementia risk.