These 10 U.S. states are predicted to have the most people with Alzheimer’s disease. Here’s why

Researchers from Rush University Medical Center in Chicago, Ill., used data from the Chicago Health and Aging Project and the U.S. Census to estimate the number of people aged 65 and older living with Alzheimer’s in every U.S. state, based on demographics.

They produced two lists: states with the largest number of people with Alzheimer’s, and states with the largest percentage of people with the disorder. As you’ll see, there’s a great deal of overlap between the two.

States with the highest prevalence of Alzheimer’s Disease (projected)

1. Maryland (12.9%)
2. New York (12.7%)
3. Mississippi (12.5%)
4. Florida (12.5%)
5. Louisiana (12.4%)
6. New Jersey (12.3%)
7. California (12%)
8. Illinois (12%)
9. Georgia (12%)
10. Connecticut (11.9%)

States with the largest number of Alzheimer’s Disease patients (projected)

1. California (719,700)
2. Florida (579,900)
3. Texas (459,300)
4. New York (426,500)
5. Pennsylvania (282,100)
6. Illinois (250,600)
7. Ohio (236,200)
8. North Carolina (210,500)
9. Michigan (202,800)
10. Georgia (188,300)

Why do some states have more Alzheimer’s patients than others? 

In the case of this analysis, the difference is just demographics, according to the authors. States with more people aged 85 and older, more women, and more non-white people (especially Black individuals) will have a greater incidence of Alzheimer’s, they write.

Why? The chance of developing Alzheimer’s disease increases with age. In fact, the risk of developing the disorder doubles every five years after the age of 65 and approaches nearly one in three by age 85, according to the Alzheimer’s Association. Women are also more likely to develop the condition; nearly two-thirds of those with it are female. And Black individuals are about two times more likely than white individuals to develop the disease and other dementias. (Hispanics are about 1.5 times more likely.)

Maryland tops the list of states with the highest prevalence of the disease because of the relatively large number of people ages 85 and older, as well as a relatively large number of Black individuals. California, Florida, and Texas top the list of states with the largest number of affected individuals because of their large senior populations.

In future studies, the research team hopes to look into the effect hearing and vision impairment, chronic health conditions, traumatic brain injury, and lifestyle factors like physical activity, social connections, and nutrition might have on these numbers, Kumar Rajan, director of the Rush Institute for Healthy Aging and author on the study, tells Fortune.

Knowing which states are prone to larger populations of Alzheimer’s disease patients helps public health officials and others put necessary resources in place, he says. If his team determines that certain factors like obesity or loneliness put seniors at a greater risk for the condition, preventative services can also be put into place.

“This is just the first step in understanding the variation of the disease across the U.S.,” he says of the study.