The incidence of dementia: a meta-analysis.

OBJECTIVE

To carry out a meta-analysis of the age-specific incidence of all dementias, including AD and vascular dementia.

BACKGROUND

Several meta-analyses have been carried out on dementia prevalence, but none on its incidence.

METHODS

We used loess-curve fitting to analyze data from 23 published studies reporting age-specific incidence data.

RESULTS

The incidence of both dementia and AD rose exponentially up to the age of 90 years, with no sign of leveling off. The incidence rates for vascular dementia varied greatly from study to study, but the trend was also for an exponential rise with age. There was no sex difference in dementia incidence (p = 0.21), but women tended to have a higher incidence of AD in very old age, and men tended to have a higher incidence of vascular dementia at younger ages. East Asian countries had a lower incidence of dementia than Europe (p = 0.0004), and also tended to have a lower incidence of AD.

CONCLUSIONS

The incidence of dementia rises exponentially to the age of 90 years. Any sex differences are small, and incidence is lower in East Asia than in Europe.