According to researchers from Finland and Sweden, people who live alone have twice the risk of developing dementia and Alzheimer's disease in later life compared with married or cohabiting people.

Being widowed or divorced in mid-life carries three times the risk of developing dementia, says study author Miia Kivipelto.

As life expectancy increases in various regions of the world, dementia is becoming a growing health concern. In 2005 an estimated 25 million people had dementia, and the number is expected to reach 81.1 million by 2040. Alzheimer’s disease is the most common form of dementia and is the sixth-leading cause of death in the United States.

Dementia is a word for a group of symptoms caused by disorders that affect the brain. Memory loss is a common symptom of dementia. However, memory loss by itself does not mean you have dementia. People with dementia have serious problems with two or more brain functions, such as memory and language.

While there have been a number of studies linking being in a couple to good health and longevity this is the first study to focus on marital status and the risk of dementia.

The researchers interviewed a random sample of men and women derived from a group of 2000 adults. The participants came from two regions in Eastern Finland. They were initially surveyed at around 50 years of age and again around 21 years later. Participants were divided into the following groups: married/cohabitant, single, divorced or widowed. The team also investigated whether there was a link between living alone and being a carrier of the ApoE4 gene variant (or allele), the known genetic risk factor for Alzheimer's.

The results reveal that people living without a partner during middle age had a higher risk of developing cognitive impairment in late life compared to those living with a partner. Individuals who become widowed at this age are three times more likely to develop dementia. The study also concluded that carriers of ApoE4 gene variant who lose their partners and remain living alone have the highest risk of developing Alzheimer's disease.

These results are important for preventing dementia and cognitive impairment. As Kivipelto explains, we now know that it would be worth offering supportive intervention for individuals who have lost a partner.
References:
1. Miia Kivipelto, et al. Association between mid-life marital status and cognitive function in later life: population based cohort study. BMJ 2009;339:b2462.
2. National Institute of Neurological Disorders and Stroke.