Alzheimer’s dementia;223 in fact, the oldest members of the baby-boom generation turned aged 75 in 2021. The incidence rate of Alzheimer’s — the number of people per 100,000 who newly develop this condition per year — appears to be declining, which has been attributed to improvements over the 20th century in Alzheimer’s risk factors, such as hypertension and low educational attainment. However, even with this potentially lower incidence rate, the number of people with Alzheimer’s is expected to continue growing because of an increase in the number of adults age 65 and over, the age group that is at increased risk of Alzheimer’s. It is unknown how COVID-19, including infection with SARS-CoV-2 (the virus that causes COVID-19), mortality from COVID-19, and changes in health care access resulting from the COVID-19 pandemic, will influence the number and proportion of people in the U.S. with Alzheimer’s. This section reports on the number and proportion of people with Alzheimer’s dementia to describe the magnitude of the burden of Alzheimer’s on communities and health care systems. The prevalence of Alzheimer’s dementia refers to the number and proportion of people in a population who have Alzheimer’s dementia at a given point in time. Incidence refers to the number or rate of new cases per year. Estimates from several studies of the number and proportion of people with Alzheimer’s or other dementias are used in this section. Those estimates vary depending on how each study was conducted. Millions of Americans are living with Alzheimer’s or other dementias. As the size of the U.S. population age 65 and older continues to grow, so too will the number and proportion of Americans with Alzheimer’s or other dementias. Prevalence of Alzheimer’s and Other Dementias in the United States An estimated 6.5 million Americans age 65 and older are living with Alzheimer’s dementia in 2022.A2,224 Seventy-three percent are age 75 or older (Figure 2).224 Of the total U.S. population: • About 1 in 9 people (10.7%) age 65 and older has Alzheimer’s dementia.A2,224 • The percentage of people with Alzheimer’s dementia increases with age: 5.0% of people age 65 to 74, 13.1% of people age 75 to 84, and 33.2% of people age 85 and older have Alzheimer’s dementia.A2,224 People younger than 65 can also develop Alzheimer's dementia. Although prevalence studies for youngeronset dementia in the United States are limited, researchers believe about 110 of every 100,000 people, about 200,000 Americans, have youngeronset dementia.225 *Percentages do not total 100 due to rounding. Created from data from Rajan et al.A2,224 65-74 years: 1.75 million (27.0%) 75-84 years: 2.41 million (37.2%) 85+ years: 2.31 million (35.7%) Number and Ages of People 65 or Older with Alzheimer's Dementia, 2022* Total: 6.5 Million 20 Alzheimer’s Association. 2022 Alzheimer’s Disease Facts and Figures. Alzheimers Dement 2022;18. Prevalence Estimates The prevalence numbers included in this report are based on an estimate of how many people in the United States are living with dementia (prevalence) and the pace at which people newly develop the condition (incidence). The estimate of 6.5 million older adults who have Alzheimer’s dementia comes from a single longitudinal study in which participants were systematically evaluated and then re-evaluated on a regular basis; those who exhibited the clinical symptoms of Alzheimer’s were classified as having Alzheimer’s dementia. A major advantage of this approach is that it attempts to capture all individuals living with the condition and does not rely on the diagnosis of people living with Alzheimer’s by the health care system, a process that has resulted in a large underdiagnosis of the Alzheimer’s population. The disadvantage is that the longitudinal study is located in a single, small geographic area and may not be nationally representative (although the modeling estimates attempt to account for the demographics of the entire U.S. population). Furthermore, it is still based on the identification of clinical symptoms to classify an individual as having Alzheimer’s instead of relying on the brain changes responsible for Alzheimer’s disease across the continuum of the disease. As data sources, methods and scientific knowledge improve, estimates of prevalence may change. First, a prevalence estimate based on the brain changes involved with Alzheimer’s, rather than clinical symptoms, is likely to be lower than the 6.5 million figure reported here. Evidence from biomarker-based studies21,69,229-231 indicates that some individuals counted as having Alzheimer’s dementia based on symptoms do not have the biological brain changes of Alzheimer’s disease; that is, their dementia is caused by something other than Alzheimer’s disease. Both autopsy studies and clinical trials have found that 15% to 30% of individuals who met the criteria for Alzheimer’s dementia based on symptoms did not have Alzheimer’s-related brain changes. Thus, these studies indicate that, compared with prevalence estimates based on the symptoms of Alzheimer’s dementia, estimates based on the biomarkers of Alzheimer’s disease could be up to 30% lower than current figures. Another potential contributor to a decrease in prevalence estimates of Alzheimer’s dementia is the use of multiple symptombased