Going through divorce, losing a partner or work problems could lead to middle-aged women developing dementia in later life, a new study suggests.
Coping with a lot of stress in middle age may heighten the risk of developing the condition, researchers said.
Common stressful life events may have "severe and long standing physiological and psychological consequences" in the brain, they say.
The research, published in the online journal BMJ Open, gathered data from a long-term study of 800 Swedish women who underwent a battery of neuropsychiatric tests when they were first selected in 1968 and again in 1974, 1980, 1992, 2000 and 2005.
At the initial assessment the women, who were all born in 1914, 1918, 1922 and 1930, were quizzed about the psychological impact on them of 18 "stressors" including divorce, widowhood, work problems and illness in a relative.
One in four women had suffered at least one stressful event, 23 per cent reported two, one in five had suffered three stressors and 16 per cent had been through four or more.
During the assessment period, 19 per cent (153) women developed dementia with 104 of these being diagnosed with Alzheimer's disease.
The number of stressors reported in 1968 was associated with a 21 per cent heightened risk of developing Alzheimer's and a 15 per cent heightened risk of developing any type of dementia, the analysis showed.
While the authors stressed that more research is needed to confirm the results of the study, they suggested that "stress may cause a number of physiological reactions in the central nervous, endocrine, immune and cardiovascular systems".
They also called for more investigations to assess whether stress management and therapy should be given to people who suffer from stressful life events.
"Our study shows that common psychosocial stressors may have severe and long-standing physiological and psychological consequences," they said.
"The study shows that the number of psychosocial stressors, measured in middle-aged women, was related to distress and incidence of Alzheimer's disease almost four decades later."
