EXPERT REACTION: Putting a ring on it could be linked to lower dementia risk

Although the authors identify that in some studies there was no difference between genders, it would have been better to understand the overall make-up of the gender mix in relation to who had dementia in the studies involved, and who was the carer. This may be seen in the supplementary material but there was no access provided.

Just being married may reduce dementia risk but may only be because of delayed recognition, diagnosis and treatment because there may be shielding of their behaviour by either the person with dementia or their carer, which is something the authors hint at.

Also, although being married is a supportive strategy for those who have dementia, it may not be for the carer who later becomes the widow or widower.

As the authors suggest, the underlying factors within the marriage need to be explored more fully and described in relation to the impact of and effect on the caregiver before concluding that marriage is, in and of itself, a factor for reducing the onset of dementia. This is because the caregiver may actually get dementia after the caregiver has been widowed.

So, in these cases, is marriage linked to a higher risk for getting dementia for those caring for a spouse with dementia?

We have known for some time that social factors play a role dementia. People with rich social interaction networks have a lower risk of dementia than those who are socially isolated.

An example relevant to Australia is the Sydney Memory and Ageing Study, which found that married couples had a lower risk of developing dementia than single persons. The strength of the current study is that it is a meta-analysis of 15 studies worldwide, with over 800,000 people in them followed for between 3-21 years. While the vast majority of subjects were Swedish, the broad range of studies suggests that the results are likely to be generally applicable.

Why marriage lowers the risk of dementia is not clear. Risk factors for dementia include low physical activity, being overweight, smoking, high blood pressure, depression and social isolation. Married couples are likely to have more social interactions than single people, especially if there is interaction with other family members such as children and grandchildren. This may also translate to more physical activity.

Couples may also notice declines in health in the other partner, with corrective action taken, more readily than singles. Translating these findings information into lifestyle modifications will require better understanding of these factors.

People who have lost a partner are at significant risk of dementia, which may be related to stress, so putting in place support networks for the elderly bereaved may be an important public health goal.

We have some evidence that modifying lifestyle may be successful, data from the UK and the US show that the incidence of Alzheimer’s disease has fallen or the past decade, most likely due to reductions in smoking and high blood pressure - known risk factors.

Identify factors that contribute to married couples lower risk may translate into interventions to lower dementia risk further.

The message to take away from this study is that Alzheimer’s risk is modifiable by lifestyle. Given there is no cure for this insidious and common disease, we must look to lifestyle factors to provide indication if we can change the course of Alzheimer's.

This analysis of many studies suggests that being single or widowed (but not divorced persons) can increase dementia risk, compared with those that are married.

Factors associated with being widowed or single are stress and social isolation, both of which are known to increase the risk of dementia. There may be other varying factors that are associated with being married that can be beneficial, ranging from diet through to sleep patters, which are also known to impact dementia.

Above all, the important message, that the disease outcome is modifiable by lifestyle factors, suggests that ultimately the Alzheimer’s disease trajectory can be changed by lifestyle, which suggests the real hope that ultimately new therapies will be found that can also assist in this disease.

This systematic review and combined analysis of previously published studies suggests that married people are at reduced risk of dementia. As the authors suggest, the findings may reflect other health and lifestyle factors which are associated with marital status. These factors may include increased physical activity and a healthy diet, which are known to help delay onset of dementia.

Another aspect of marriage might be increased long-term social interaction, which is a form of cognitive stimulation also known to be protective with respect to dementia. However, it should be noted that this research involved ‘observational studies’ in participants from the general population, and not long-term studies of those people during their lifespans, so cause and effect is difficult to determine.

Furthermore, as this was a re-analysis of previous studies, it may reflect the lifestyles (and possibly other attributes) of those who were married or single in the 20th century, and these differences may not hold in the 21st century.

While more research is needed, I think it is generally consistent with the public health message that our ‘enviromes’ (total environmental exposures throughout life) and lifestyles (including physical activity and diet) not only affect our bodies, but also our brain health.