A large, long-term study reveals that dealing with stress during middle age may trigger lasting physiological brain changes, increasing the risk of developing dementia later in life.

This finding comes from the Prospective Population Study of Women in Gothenburg, Sweden, which started in 1968 and followed over 800 Swedish women for around 40 years. Results of the study were published online in the journal BMJ Open.

Researchers from the study looked at previous studies showing how stress can cause both structural and functional brain damage, as well as promote inflammation.

They say stress hormones can remain at high levels, long after a traumatic event has passed.

Previous studies looked at the effect of severe psychological stressors in adulthood, such as combat, natural disasters and the Holocaust, and they revealed that mental and physical health were affected decades later.

However, the researchers say that although mild psychosocial stressors are a regular part of life, the “long-term consequences of these more common stressors” have remained unclear.

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Women who experienced certain stressors during middle age had a 21% increased risk for Alzheimer’s and a 15% increased risk for dementia, according to the study.

The women who were part of this recent study were all born in 1914, 1918, 1922 and 1930. They underwent neuropsychiatric tests and exams in 1968, and then again in 1974, 1980, 1992, 2000 and 2005.

In 1968, at the start of the study, the women were asked about the psychological impact of 18 common stressors, including divorce, widowhood, illness or death of a child, mental illness or alcoholism in a family member, unemployment and poor social support.

At each follow-up visit, researchers documented how many symptoms of distress – irritability, fear or sleep disturbances – each woman had experienced in the preceding 5 years.

One in four of the women had experienced a minimum of one stressful event at the start of the study. The most common stressor was mental illness in a close family member (sibling 32%, mother 27%, father 19%).

Between the monitoring period of 1968 and 2006, about one in five – 153 in total – of the women developed dementia, and 104 of them developed Alzheimer’s disease.

Dementia was diagnosed at an average age of 79, and it took 29 years for it to develop, the researchers say.

The number of stressors the women reported in 1968 was associated with a 21% increased risk of developing Alzheimer’s disease and a 15% increased risk of developing any kind of dementia, according to the study.

The researchers note that these findings remained the same, even after factoring in elements that could influence the results, such as a family history of mental health problems.

Though the study concludes the research does indeed show that common psychosocial stressors have long-term consequences, the authors say that more studies are needed to confirm the results.

They also recommend further study of interventions, such as stress management and behavioral therapy, to see whether these could be useful for people who have experienced the contributing stressors.

Dr. Lena Johansson, co-author of the study, told Medical News Today that she and her colleagues are planning to continue the research project and extend it to a sample of men in a study taking place in Gothenburg, in order to further analyze the relationship between stressors and dementia.