Incidence of Young Onset Dementia in Central Norway: A Population-Based Study.

BACKGROUND: The epidemiology of young onset dementia is little researched compared to late onset dementia. Information on incidence rates is vital for medical professionals, and for government planning purposes. OBJECTIVE: To determine the incidence of young onset dementia in a defined catchment area of central Norway. METHODS: The target area was Trondelag county in central Norway with a total population of 449,796 inhabitants per January 1, 2016. We applied multiple case ascertainment strategies with sources from both primary and secondary healthcare facilities. Included patients received a diagnosis of dementia according to DSM-IV in the ages 30 to 64 years during the years 2015-2017. Subtypes of dementia were diagnosed according to standardized criteria. Incidence rates for dementia and Alzheimer's disease with dementia were calculated according to age and sex. RESULTS: A total of 89 incident cases were included. Incidence rates for dementia were 14.8 and 25.0 per 100,000 person-years for the age range 30-64 and 45-64, respectively. Corresponding incidence rates for Alzheimer's disease were 6.7 and 11.8. Alzheimer's disease represented half of all dementias. A majority of patients above the age of 50 had neurodegenerative disease, whereas non-degenerative disorders were more prevalent in younger patients. CONCLUSION: Young onset dementia is a significant contributor to the overall occurrence of dementia in central Norway, and Alzheimer's disease is by far the most common diagnosis.