Dementia rates vary sharply across U.S. regions

A study of older U.S. veterans found that dementia incidence was lowest in the Mid-Atlantic region (11.2 cases per 1,000 person-years) and highest in the Southeast (14.0 cases per 1,000 person-years). The paper was published in JAMA Neurology.

Dementia is a broad term for a group of symptoms affecting memory, thinking, and social abilities severely enough to interfere with daily life. It is most commonly caused by Alzheimer’s disease, but other types include vascular dementia, Lewy body dementia, and frontotemporal dementia. Dementia is progressive, meaning symptoms worsen over time.

Early signs can include forgetfulness, difficulty finding words, and trouble with problem-solving or planning. As the condition advances, individuals may struggle to recognize familiar people, perform routine tasks, or regulate emotions. Although aging is the greatest risk factor, dementia is not a normal part of aging. Genetics, cardiovascular health, head injuries, and lifestyle factors also contribute to risk. Research suggests that maintaining physical activity, cognitive engagement, and a healthy diet may help reduce the likelihood of developing dementia.

Study author Christina S. Dintica and colleagues sought to investigate whether dementia incidence varies across U.S. regions. They focused on older veterans enrolled in the Veterans Health Administration (VHA), the largest integrated healthcare system in the United States.

The analysis included 1,268,599 veterans aged 65 years or older who received care at VHA medical centers between October 1999 and September 2021. This group represented a randomly selected sample of about 5% of older veterans who used VHA services during those years. The average age was 73.9 years, and 2% were women.

To be included, participants had to have known zip code information so that researchers could determine their geographic location. Those without a zip code were excluded. Dementia diagnoses were identified using medical records.

Based on their zip codes, participants were classified into one of 10 U.S. regions, each composed of 4 to 7 states: Southeast (Kentucky, Tennessee, Alabama, and Mississippi); Southwest (Arizona, California, Hawai‘i, and Nevada); South Atlantic (North Carolina, South Carolina, Georgia, and Florida); South (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas); Rocky Mountains (Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming); Northwest (Alaska, Idaho, Oregon, and Washington); Northeast (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, and New York); Midwest (Iowa, Kansas, Missouri, and Nebraska); Mid-Atlantic (Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia, and New Jersey); and Great Lakes (Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin).

The lowest dementia incidence was observed in the Mid-Atlantic (11.2 per 1,000 person-years) and the highest in the Southeast (14.0 per 1,000 person-years). Compared with the Mid-Atlantic, dementia risk was 25% higher in the Southeast, 23% higher in both the Northwest and Rocky Mountains, 18% higher in the South, and 12% higher in the Midwest and South Atlantic. In the remaining regions, rates were less than 10% higher than in the Mid-Atlantic.

“Among older adults in the VHA, dementia incidence varied significantly across US regions, independent of key covariates. These findings highlight the need for targeted health care planning, public health interventions, and policy development,” the study authors concluded.

The study sheds light on the regional variation in dementia incidence rates. However, it should be noted that the design of the study does not allow any causal inferences to be derived from the results. While the study reported differences between geographical regions, the specific factors underlying these regional variations remain unknown.

The paper, “Regional Differences in Dementia Incidence Among US Veterans,” was authored by Christina S. Dintica, Amber L. Bahorik, Feng Xia, John Boscardin, and Kristine Yaffe.