Take a moment to consider how old you feel. Not your actual, biological age – but your own subjective feelings.
Abundant research during the past few decades has shown that this “subjective age” can be a powerful predictor of your health, including the risk of depression, diabetes and hypertension, dementia, and hospitalisation for illness and injury, and even mortality – better than your actual age. In each case, the younger you feel, the healthier you are.
The link probably goes in both directions. So while it’s true that ill-health may make you feel older, a higher subjective age could also limit your physical activity and increase feelings of vulnerability that make it hard to cope with stress – both of which could, independently, lead to illness. The result could even be a vicious cycle, where feelings of accelerated ageing lead you to become more inactive, and the resulting ill-health then further confirms your pessimistic views. And as I recently wrote for BBC Future, understanding this process could be essential for designing more effective health programmes.
Yannick Stephan at the University of Montpellier has led much of the work examining this phenomenon, and his latest paper, published with colleagues in the journal Intelligence, extends this understanding by revealing a surprising link with IQ. According to this research, the more intelligent we are in our late teens and early 20s, the younger we will feel in our 70s – and this may also be reflected in various markers of biological ageing.
Stephan’s team’s analysis is based on data from the Wisconsin Longitudinal Study, which for many years has tracked thousands of men and women born between 1937 and 1940. In 1957, each member of the study took an IQ test, which Stephan then compared to their estimated subjective age, taken more than 50 years later in 2011.
In line with other studies, the average participant felt about 17 per cent younger in their 70s than their actual age – but the precise difference depended on their adolescent intelligence (those participants who’d had higher teen IQ felt even younger), a link that remained even when the analysis controlled for the influence of demographic factors.
After establishing this basic correlation, Stephan’s team also looked for other personal characteristics, such as education level and different personality traits, that might mediate the relationship. They found that greater “openness to experience”, which is associated with havinga higher IQ, seemed to be important. Perhaps a higher IQ, which helps us to process complex information more easily, also increases our curiosity about the world, and it’s that sense of wonder and excitement that can make us feel more youthful.
Having higher intelligence might also make it easier to cope with the challenges that come with age, so that we don’t feel so vulnerable to our changing circumstances. And people with higher IQ may also be better able to deconstruct the negative age stereotypes that might otherwise place limits on our behaviour and lead to greater feelings of vulnerability.
The study chimes with others that have similarly linked a higher childhood IQ to various signs of biological ageing, including the length of our cells’ telomeres (the protective “caps” on the end of chromosomes that tend to shorten over the lifespan) and epigenetic markers.
Given that lower subjective age appears to encourage healthier behaviours, these new findings could help to explain these earlier IQ-ageing correlations. But once again, we should be wary of oversimplifying these relationships. A higher IQ could easily enhance our health through other pathways, such as the socioeconomic advantage that comes with better education.
Stephan’s paper can’t unpick all these mechanisms, but it could certainly provoke some fascinating future research on the ways our cognitive abilities influence the ageing process.
I’d be particularly interested to see similar studies that look beyond the reasoning found on traditional intelligence tests. As Research Digest explored last year, our critical thinking skills (such as how well we are able to dispassionately evaluate an argument), are more predictive than our basic IQ of the likelihood we will experience many life events – from the small stresses such as losing your passport to getting divorced, falling into debt, or catching a sexually transmitted diseases.
Might other measures of “good” thinking, prove to have an even closer link to the measures of subjective and biological ageing? It would be fascinating to see if these skills – which can be taught – could also help people cope with the challenges of old age, by reducing stressful mistakes and encouraging healthier behaviours, and by helping us to question age stereotypes.
In the meantime, Stephan’s paper provides one more fascinating example of the far-reaching effects of our thinking and reasoning abilities, far beyond their obvious influence over our academic and professional success.