(Reuters Health) - Hailing from the so-called stroke belt, a band of southern U.S. states with high stroke mortality rates, is associated with increased odds of developing dementia, even for people who relocate, a new study suggests.

Previous research has linked what are known as vascular risk factors, including obesity, diabetes, smoking, high cholesterol and elevated blood pressure, to higher odds of both dementia and stroke.

For the current study, researchers examined data on 7,423 adults living in Northern California, including 1,166 people born in high stroke-mortality states - all but one in the South: Alabama, Alaska, Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee, South Carolina and West Virginia.

At age 65, the risk of developing dementia in the next 20 years was 30 percent for people born in these states, compared to 21 percent for those born elsewhere, the study found.

“We know that where someone was born can influence how likely they are to have a stroke,” said lead study author Paola Gilsanz of the University of California, San Francisco and the Kaiser Permanente Northern California Division of Research in Oakland.

“But as far as we know this is the first paper to look at the association between the place of birth and dementia,” Gilsanz said by email.

All of the patients in the current study had insurance through Kaiser Permanente in Northern California. Researchers examined medical record data for these Kaiser members starting between 1964 and 1973, when they were middle aged, and continuing through 1996 to 2015, when they were elderly.

Overall, 2,254 people, or 30 percent, were diagnosed with dementia during the study period, researchers report in JAMA Neurology.

Dementia was more common in people born in the high stroke-mortality states, however, affecting 39 percent of people from those nine states, compared to 29 percent of adults born elsewhere.

After accounting for age, sex and race, the study authors calculate that having been born in one of the high stroke-mortality states is associated with 29 percent higher odds of dementia later in life compared to people born in other parts of the U.S.

Black people in the analysis were almost 10 times more likely to have been born in one of the stroke belt states, though, and had the highest dementia risk of all.

Black adults from the nine states with high stroke mortality rates were 67 percent more likely to develop dementia than non-black people born outside of the stroke belt. Black people born outside the stroke belt were 48 percent more likely to develop dementia than all others born outside the stroke belt.

Non-black adults born in the states with high stroke mortality rates were 46 percent more likely to develop dementia than non-black people born elsewhere, the study also found.

The study wasn’t a controlled experiment designed to prove whether or how birth in a state with high stroke mortality rates might influence the odds of dementia.

Researchers also lacked data on how long people lived in their state of birth or other places in the U.S., making it impossible to determine how long people might have lived in the stroke belt or whether their age when they moved away influenced their odds of dementia, the authors note.

Even so, people should be aware of the similar risk factors for stroke and dementia and focus early on prevention, especially if they’re from a region where stroke mortality rates are unusually high, said Daniel Lackland, author of an accompanying editorial and a researcher at the Medical University of South Carolina in Charleston

Among other things, people should check their blood pressure regularly and adopt healthy lifestyle habits like eating a low-salt diet and getting plenty of exercise, Lackland said by email.

Both the American Heart Association and the Alzheimer’s Association have good prevention guides online, Gilsanz said (bit.ly/1Owhr6f ).

“If you were born in a high risk state and move to a low risk state, you take the risk with you unless you modify your lifestyle and control your risk factors,” Lackland said. “The good news is that with a reduction in risk factors the risk of both stroke and dementia can be reduced.”

SOURCE: bit.ly/2f1vOWw and bit.ly/2tSgePw JAMA Neurology, online July 31, 2017.