Depression increases risk of dementia

People who experience depression have more than a 50% increased risk of developing dementia or Alzheimer's disease later in life, according to a study published in Neurology, the medical journal of the American Academy of Neurology.1

Researchers examined data on 949 people with an average age of 79 from the Framingham Heart Study. At the start of the study, participants were free of dementia and were tested for depressive symptoms, based on questions about general depression, sleep complaints, social relationships, and other factors. A total of 125 people, or 13%, were classified as having depression at the start of the study.

The participants were followed for up to 17 years. At the end of the study, 164 people had developed dementia, with 136 specifically diagnosed with Alzheimer's disease. Nearly 22% of people who were depressed at the start of the study developed dementia compared to about 17% of those who were not depressed, a 70% increased risk in those who were depressed. The 10-year absolute risk for dementia was 0.21 in people without depressive symptoms and 0.34 in people with depressive symptoms. The results were the same regardless of a person's age, sex, education and whether they had the APOE gene that increases a person's risk of Alzheimer's disease.

Researchers point out that it is unclear if depression causes dementia, but there are ways that depression can impact the risk of dementia. Inflammation of the brain tissue, along with an increase in certain proteins in the brain that occurs in depression, might contribute to dementia, the authors suggest. Lifestyle factors affected by long-term depression, such as quality of diet and amount of exercise and social interaction, might also affect the risk of developing dementia, they point out.

Reference

Saczynski JS, Beiser A, Seshadri S, et al. Depressive symptoms and risk of dementia. Neurology 2010;75:35-41.