Posted on 3 January 2022
Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.
Why is this research important: There is a well established relationship between lack of social relationships and mortality. On average, people with more social relationships tend to live longer, and research suggests that this relationship is very strong – comparable even to risk factors such as smoking or physical inactivity. Yet proving that lack of social relationships causes a shorter lifespan is not easy. Since we can’t randomly assign people to have no social contact and record how long they live, the relationship could be explained by debilitating diseases causing a decline in social activities, rather than the other way around.
What did the researchers do: Here, researchers performed a meta-analysis of 148 prospective studies (with an average follow-up of 7.5 years) on mortality as a function of social relationships. These included a total of 308 849 participants, mostly from North America (51%) and Europe (37%). Prospective studies examine factors of interest (in this case social relationships) at the start of the study period, then follow participants over time in order to observe outcomes (in this case mortality). In this meta-analysis, researchers extracted the data from each study and used it to calculate the odds ratio – the ratio between the probability of death in people with stronger social relationships compared to those with weaker social relationships.
Not all studies within the meta-analysis used the same measurements of social integration. Some used simple criteria such as whether participants ‘lived alone’, which doesn’t necessarily correspond to social isolation, while others used more complex measurements such as the size, diversity and level of participation in social networks. The authors of the meta-analysis studied whether the complexity of these measurements influenced the strength of the observed relationship between social connections and mortality.
Key takeaway(s) from this research: The researchers report an average odds ratio of 1.5 – that is to say that people with stronger social relationships were 50% more likely to still be alive at the end of a study period than those with weaker social relationships when all of the studies are considered as a whole. When researchers broke the studies down according to how social relationships were measured, they found that more complex measurements correlated more strongly with mortality. Simple, binary measurements (such as whether participants lived alone) were the least predictive of mortality, while multidimensional assessments of social integration yielded the strongest association: a 91% increase in odds of survival.
These are very strong reductions in mortality, comparable to that of quitting smoking. As already mentioned, this doesn’t prove that lack of social relationships causes increased mortality. However, the authors argue that a relationship of this size is unlikely to be explained by illnesses restricting social relationships, because they found no significant relationship between initial health status and the effects of social connections on mortality. In other words, a person with strong social connections was still 50% more likely to survive than someone with weak social connections, regardless of how healthy they were at the start of the study.
There are other confounding factors that could be responsible for this relationship, such as age, sex, and economic status. While most of the included studies did control for these factors, different studies used different approaches to do so, and it’s impossible to perfectly control for every single confounding factor.
Even if not all of the observed association is causal, this study still suggests that the importance of social relationships when it comes to health is undervalued compared to more tangible risk factors such as exercise and diet. Social relationships may influence health through ‘stress buffering’, providing forms of support that help people adapt in the face of stressful life events or illness. Being part of a social network also provides self-esteem and may promote other healthy behaviours and self-care.
Social Relationships and Mortality Risk: A Meta-analytic Review: https://doi.org/10.1371/journal.pmed.1000316