By Makiko Kitamura

Stress in middle age may contribute to development of Alzheimer’s disease later in life, according to a Swedish study spanning almost 40 years.

imagesPsychological stress was associated with a 21 percent greater risk of developing Alzheimer’s disease, according to a study of 800 Swedish women born between 1914 and 1930 who underwent neuropsychiatric tests periodically between 1968 and 2005. The research, led by Lena Johansson at the Sahlgrenska Academy at the University of Gothenburg was published today in the journal BMJ Open.

“This suggests that common psychosocial stressors may have severe and long-standing physiological and psychological consequences,” the authors said in the published paper.

The research points to a potential non-medical approach to preventing some cases of dementia, which afflicts at least 35.6 million people globally, according to the Geneva-based World Health Organization. No drugs on the market have been shown to slow progression of the disease. While more studies are needed to confirm the results, interventions such as stress management and behavioral therapy should be investigated, the authors said.

During the monitoring period, 153 women, about a fifth of the total, developed dementia, diagnosed at the average age of 78. About half the women died, at the average age of 79.

Biological Mechanisms

A quarter of the women reported at least one stressor, with mental illness in a family member the most common. The link between psychological stressors and dementia can be explained through a variety of biological mechanisms, such as causing structural and functional damage to the hippocampus, which plays a role in memory and spatial navigation, as well as increasing build-up of beta amyloid plaque and tau protein, typical signs of Alzheimer’s, according to the study’s authors.

“From this study, it is hard to know whether stress contributes directly to the development of dementia, whether it is purely an indicator of another underlying risk in this population of women, or whether the link is due to any entirely different factor,” said Simon Ridley, head of research at Alzheimer’s Research U.K., a Cambridge-based charity.

“An important next step will be to investigate the potential reasons for the observed association between midlife stress and dementia risk.”

The research was funded by organizations including the Swedish Medical Research Council, the Swedish Council for Working Life and Social Research and the U.S. National Institutes on Aging.