People who smoke or who have high blood pressure or diabetes in middle age are more likely to develop dementia, a new study has found.

The good news is that people who take steps to curb these risk factors in their 50s and 60s might have a better shot at avoiding Alzheimer’s disease and other forms of dementia in their 70s and 80s.

“People need to know that quitting smoking or controlling high blood pressure or diabetes is going to be beneficial not only for reducing the risk of heart attack, cancer, or stroke now, but also for reducing the risk of dementia later,” the study’s lead author, Dr. Alvaro Alonso, assistant professor of epidemiology at the University of Minnesota School of Public Health in Minneapolis, told Reuters Health in a telephone interview.

The study, published in the latest issue of the Journal of Neurology, Neurosurgery & Psychiatry, also showed that the link between the three risk factors and subsequent dementia holds true for African-Americans as well as for whites. Overall, African-Americans were 2.5 times more likely than whites to be hospitalized for dementia.

Similar studies conducted previously included African-Americans only in small numbers or excluded them entirely, Alonzo said.

Dementia is a growing problem in the US. One in six Americans over the age of 70 has dementia. By 2050, the number of Americans with dementia is projected to be three times higher than what it was in 2000.

The study involved 11,151 men and women who were between the ages of 46 and 70 when they joined the study in 1990-1992. At the start of the study, Alonso and his colleagues used physical exams and tests of memory and mental agility to assess each participant’s health. They followed each participant through December, 2004, during which time 203 people were hospitalized for dementia.

People who had diabetes in middle age were twice as likely as those without diabetes to develop dementia later in life. Middle-aged smokers were 70 percent more likely than people who had never smoked to develop dementia, and middle-aged people with high blood pressure were 60 percent more likely to develop dementia than people whose blood pressure was normal in middle age.

No increased risk of dementia was seen in people who were overweight or obese in middle age or for those who had High cholesterol in midlife.

In an accompanying editorial, Dr. Stephanie Debette of the Pasteur Institute in Lille, France, and Dr. Sudha Seshadri of Boston University School of Medicine said the study’s findings seem to support the notion that reducing risk factors in middle age could help prevent dementia - but that this hadn’t yet been proved.

Dr. Nikolaos Scarmeas, associate professor of neurology at Columbia University Medical Center in New York City, agreed, telling Reuters Health in an email that “whether control of such [risk] factors will lower dementia risks remains to be demonstrated in future clinical trials.”

The study was conducted as part of the ongoing Atherosclerosis Risk in Communities study. Begun in year 1987, the ARIC study is tracking the health of almost 16,000 residents of four US communities: Forsyth County, North Carolina; Jackson, Mississippi; Washington County, Maryland; and the suburbs of Minneapolis.

SOURCE: Journal of Neurology, Neurosurgery & Neuropsychiatry, November, 2009.