Andrew Sommerlad and Marko Elovainio
Dementia is the most feared aspect of ageing and is a major global health challenge, so identifying lifestyle factors that can reduce memory decline, and possibly prevent dementia from occurring, is a research priority. In our study, recently published in the IJE, we explored whether having more frequent contact with friends and family, or being married, is linked to better memory and language in older age.
We found that having more social contact and being married in mid-life were both linked to having better cognitive performance over the next 20 years. In particular, we found that verbal fluency was the cognitive area with the strongest link to social contact.
Our study cannot tell us the direction of the relationship — whether social contact is the cause of better cognitive performance, or its effect. To do this, we would need to test whether active measures to increase people’s social contact in their middle-aged years strengthen cognition in later life. Considering that nearly three-quarters of older people report feeling lonely, taking such measures may make a difference to their quality of life as well as their cognition.
For our study, we used the Whitehall II cohort of 10,000 London-based civil servants (including manual and clerical staff and those from higher professional grades) who were first interviewed in the mid 1980s and continue to have their physical, mental and cognitive health assessed at 5-yearly intervals. Whitehall is one of the UK-based research studies that were originally set up to examine influences on general physical health, and it is now being used to examine the priority research areas of cognition and dementia risk.
We used data from Whitehall interviews between 1985 and 1990 in which participants were asked:
- how often they saw family and friends and how often they participated in social and religious activities (scored on a 28-point scale), and
- whether they were married — we saw this as another way of measuring social contact, as other studies have suggested that being married leads to more lifetime social contact.
To assess cognition, we used three different tests, measured on five occasions over the subsequent 20 years. To assess memory, we showed participants 20 words and asked them to recall as many as possible 2 minutes later. For verbal fluency, we asked people to think of as many animals and then as many words beginning with “s” as possible in 1 minute. Finally, to assess verbal and mathematical reasoning, we used a timed test in which we asked a series of increasingly difficult reasoning questions.
From the results of these tests, we identified three distinct subgroups of study participants who had similar patterns of cognitive change throughout the study period, which we classified as high, intermediate or low cognitive performance. The graph below shows the average cognitive change in the three groups across the 20 years. From the initial average performance results, there was a slight increase in performance at the second test for the high and intermediate cognitive performance groups, which we believe was because the participants were more familiar with the test on the second sitting (the “practice effect”). All groups then had a gradual decline in cognitive performance over the next 15 years.
We then analysed whether people’s previous social contacts influenced their cognitive trajectory and found that each extra point scored on the social contact scale (such as seeing family weekly rather than monthly) was linked to a 4% lower chance of being in the low cognitive performance group. People who were married had a 30% lower risk than those who were unmarried. These findings held true even when we took into account a range of other health and lifestyle factors, such as age, sex, ethnicity, weight and alcohol consumption.
Although other research studies have previously found a link between infrequent social contact and lower cognitive ability, our study had the advantage of using data with a long follow-up and multiple measurements of cognition, which helped us to better understand the long-term outcomes. As well as testing whether these results hold true in other populations, a potential next step is to test whether improving social contact can have benefits for cognition. However, finding effective ways to do this that would be acceptable to the most socially isolated groups, many of whom may be reluctant to make changes, is a major challenge. Overcoming this challenge could have substantial benefits for individuals and society.
Elovainio M, Sommerlad A, Hakulinen C, et al. Structural social relations and cognitive aging trajectories: evidence from the Whitehall II cohort study. International Journal of Epidemiology, dyx209, https://doi.org/10.1093/ije/dyx209.
Andrew Sommerlad is a Wellcome Trust Research Fellow at the UCL Division of Psychiatry and an old-age psychiatrist at Camden and Islington NHS Foundation Trust. His research focuses on social engagement and dementia, including whether social contact protects against the disorder, and the effect of social isolation on the likelihood of receiving a dementia diagnosis. (Twitter: @atsommerlad)
Marko Elovainio has tenure as a professor of psychology at the University of Helsinki and part-time tenure as a research professor at the Finnish National Institute for Health and Welfare. His research has focused on social epidemiology, intergenerational transmission of health, occupational health psychology and the risk factors for depression, cardiovascular diseases and type 2 diabetes.