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 Trøndelag 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.