By Kathryn Doyle
NEW YORK (Reuters Health) - Middle-aged women with lots of stress are more likely to develop Alzheimer's disease down the road, a new study suggests.
Why that might be the case is still a mystery, lead author Lena Johansson from the Institute of Neuroscience and Physiology at Gothenburg University in Mölndal, Sweden, said.
It's also difficult to say how important stress may be in predicting dementia compared to many other influences like poverty, diet, smoking and blood pressure, she told Reuters Health. But the link remained after the researchers took those factors into account.
"I have no reason to think that this relation is not the same among men," Johansson added.
The new data come from a large study of Swedish women started in 1968, when participants were at least 38 years old. Researchers surveyed 800 of those women about their mental health and wellbeing at least once every decade until 2005.
For their study, Johansson and her colleagues looked at women's reporting of 18 stressful life events like divorce, widowhood or a relative's illness and how distressed they felt by those events.
They also consulted hospital records and results of neuropsychiatric exams to track which participants were diagnosed with dementia during the study.
By 2005, 153 women had developed dementia, including 104 with Alzheimer's disease, the researchers report in BMJ Open.
They found that for each additional stressor women reported in 1968, their risk of later developing Alzheimer's disease increased by about 20 percent.
Women who reported long-term distress also had a heightened risk of Alzheimer's, regardless of how many stressful life events they had experienced.
The study does not prove cause and effect, and some other factor common to the women might account for their risk of later dementia.
Still, Robert S. Wilson, who studies Alzheimer's disease at Rush University Medical Center in Chicago, said, "This is the best evidence by far to date linking psychosocial stressors with dementia. It's really astounding."
He said it was especially impressive that the study was able to link life events, not just how stressed women felt, to later dementia.
Everyone reacts to stressful events differently, but these events seemed to have a similar effect across the board, said Wilson, who was not involved in the study.
"These are low-level chronic stressors that affect virtually every family network," he told Reuters Health.
Still, people who have lost a spouse, been divorced or experienced other stressful events shouldn't necessarily be worried, he said.
"I think these are modest effects overall," Wilson said.
"Stress and stressors are just one of several risk factors," Johansson said. "Not everyone who had stress or stressors developed (dementia)."
By age 85, nearly half of people may have Alzheimer's disease, according to the U.S. Centers for Disease Control and Prevention.
"These problems are very common, and they are of definite public health importance," Wilson said. "I think we should be thinking about stress reduction as a more routine kind of healthcare option."
What many people think of as common life events may continue to cause distress for years, he said, and stress reduction techniques like "talking it out" or seeking professional help might be beneficial.
SOURCE: http://bit.ly/19J7pp0 BMJ Open, online September 30, 2013.