Two main measures are used in epidemiological studies: incidence and prevalence. Incidence is the number of new cases per unit of person-time at risk (usually number of new cases per thousand person-years); while prevalence is the total number of cases of the<unk>  in the population at any given time. Deaths per million persons in 2012 due to dementias including<unk>  Regarding incidence, cohort longitudinal studies (studies where a<unk> -free population is followed over the years) provide rates between 10 and 15 per thousand person-years for all dementias and 5–8 for<unk> , which means that half of new dementia cases each year are<unk> .<unk> vancing age is a primary risk factor for the<unk>  and incidence rates are not equal for all ages: every 5 years after the age of 65, the risk of acquiring the<unk>  approximately doubles, increasing from 3 to as much as 69 per thousand person years. Females with<unk>  are more common than males, but this difference is likely due to women's' longer life spans. When<unk> justed for age, both sexes are affected by<unk> 's at equal rates. In the United States, the risk of dying from<unk>  in 2010 was 26% higher among the non-Hispanic white population than among the non-Hispanic black population, and the Hispanic population had a 30% lower risk than the non-Hispanic white population. The prevalence of<unk>  in populations is dependent upon factors including incidence and survival. Since the incidence of<unk>  increases with age, prevalence depends on the mean age of the population for which prevalence is given. In the United States in 2020,<unk> 's dementia prevalence was estimated to be 5.3% for those in the 60–74 age group, with the rate increasing to 13.8% in the 74–84 group and to 34.6% in those greater than 85. Prevalence rates in some less developed regions around the globe are lower. As the incidence and prevalence are steadily increasing, the prevalence itself is projected to triple by 2050. As of 2020, 50 million people globally have<unk> , with this number expected to increase to 152 million by 2050.
Alzheimer's disease
Lewy body dementias
Parkinson's disease dementia
Down syndrome
Vascular dementia
Aging brain
Alcohol-related dementia
Chronic traumatic encephalopathy