Results showed that positivity and psychological quality of life improved after stopping smoking. Christopher Meredith/Flickr

Experiencing severe stress during middle age can increase a woman's risk of developing Alzheimer's disease and dementia.

Alzheimer's disease is a brain disease that leads to the destruction of memory and other important functions of the brain, including thinking, communication and behaviour. According to Fisher Center for Alzheimer's Research Foundation in the US, the disease strikes every 68 seconds.

Alzheimer's disease is one of the most common causes of dementia, a syndrome related to the brain that leads to memory loss, difficulty in communicating, thinking, understanding, judgement, planning and the ability to perform daily routines. According to the World Health Organization, nearly 35.6 million people around the world are affected with dementia and nearly 7.7 million new cases are reported every year.

The new study followed 800 Swedish women for 40 years. The women were part of the larger Prospective Population Study of Women in Gothenburg, Sweden. Mental health status of the women was examined through various tests at regular periods. The first one was conducted in 1968, when the women were in their late 30s and later in their mid-40s, 50s and at regular intervals until the women reached their 70s.  

Researchers analysed prevalence of some stressful life events among the participants, including divorce, health issues of children, alcohol abuse in the family, unemployment issues, death of husband or child, mental illness in the family and lack of enough social support. Apart from these, during every examination, they noted down stress-related symptoms in the participants like fear, sleep deprivation, distress and irritability.

Apart from the 425 who died during the trial period, 153 developed dementia and another 104 developed Alzheimer's disease. Researchers found that exposure to severe stress during the 30s increased the risk of developing Alzheimer's disease by 21 percent or any other type of dementia by 15 percent.

The results didn't change even after some other factors that influence the brain diseases were taken into consideration.

The study published in the British Medical Journal found that stress can leave a lasting impact on the brain and supported previous studies that linked structural and functional brain damage and inflammation to stress.

While explaining their study, the authors said that "stress may cause a number of physiological reactions in the central nervous, endocrine, immune and cardiovascular systems."

Report shows that prevalence of both Alzheimer's disease and dementia is low in India compared to developed countries. Some factors that increase the risk of these brain diseases are excessive cleanliness, ageing, going through head trauma, family history of the disease, genetic mutations, unhealthy lifestyle including smoking, poor diet and lack of exercise.