The build up of psychological stress in middle age, a new research from the University of Gothenburg, Sweden, has found, could lead to the development of dementia later in life.
Based on data from a study, which followed women for 35 years, this is the first research in Sweden to indicate a link between stress and dementia.
The research is based on a major population study of women from Gothenburg. A representative sample of women were examined for the first time in 1968 when aged between 38 and 60, and then re-examined in 1974, 1980, 1992 and 2000.
A question about psychological stress was included in the 1968, 1974 and 1980 surveys and was answered by 1,415 women.
"Stress was defined as a sense of irritation, tension, nervousness, anxiety, fear or sleeping problems lasting a month or more due to work, health, family or other problems," said Lena Johansson, a researcher from the Neuropsychiatric Epidemiology Unit at the Sahlgrenska Academy's Department of Psychiatry and Neurochemistry at the University of Gothenburg.
During the 35 years of the study, 161 of the participants developed dementia, mainly in the form of Alzheimer's disease.
The risk of dementia was about 65 percent higher in women who reported repeated periods of stress in middle age than in those who did not. In women who reported stress in all three surveys, the risk more than doubled.
"This is the first study to show that stress in middle age can lead to dementia in old age, and confirms similar findings from studies of animals. Stress has previously been shown to increase the risk of cardiovascular diseases such as stroke, heart attack and hypertension," said Johansson, who also refers to earlier research at the Sahlgrenska Academy showing that cardiovascular disease can lead to Alzheimer's.
"This study could result in a better understanding of the risk factors for dementia, but our results need to be confirmed by other studies, and further research is needed in the area. Most of those who said that they were stressed did not develop dementia, so it's not currently possible to advise people to be less stressed or warn about the dangers of high stress levels due to an increased risk of developing dementia."
The study has been published in prestigious scientific journal Brain.