Subjects: Behavioral health
Martin Seligman is the originator of an increasingly mainstream theory of health and behavior known as Positive Health. His theory suggests that we should cultivate and maintain ‘positive health assets’ – things like optimism, connectedness, a stable marriage and so forth – because they contribute to a healthier, more fulfilling life and improved life expectancy as well.
In earlier posts on the matter, I reviewed 2 studies that support Seligman’s theory. In the first, Harvard scientists showed that emotional and cognitive well-being was associated with a reduced rate of coronary events. In the second, University of Michigan scientists showed that optimism was an independent predictor of short term stroke risk.
Recently, scientists at the Karolinska Institutet undertook to study this aspect of Positive Health. Once again, the findings support Seligman’s concept.
As was the case for the first 2 studies, support for the new study was provided by the Robert Wood Johnson’s Pioneer Portfolio.
In the new study, Francisco Ortega and colleagues set-out to study the association between psychological well-being and cardiorespiratory fitness, and their combined effects on survival.
The scientists used data from the Aerobics Center Longitudinal Study (ACLS), a prospective epidemiologic investigation of more than 5,000 volunteers that began in 1988. At the time of enrollment, participants had a thorough clinical evaluation including a history, physical exam, blood chemistry tests and an exercise test. Participants ranged in age from 20-81. They were followed annually until they died or the study ended, in 2003.
In ACLS, psychological well-being was evaluated at the time of enrollment using negative and positive emotion subscales from the Center for Epidemiologic Studies depression (CES-D) test. Questions in this test asked about how frequently respondents experienced certain feelings in the preceding week. The negative emotion subscale included things like ‘my life had been a failure’, ‘not able to shake off the blues’, and ‘depressed’. The positive emotion subscale included things like ‘feeling as good as other people’, ‘happy’ and ‘hopeful’.
What Did They Find?
After adjusting for traditional cardiovascular risk factors, the scientists found that participants with low levels of negative emotion had a 34% lower risk of death than peers reporting high levels of negative emotion. The protective effect was localized to those with high levels of cardiorespiratory fitness (CRF): high levels of CRF were themselves associated with a 46% reduction in mortality risk, but in the subset of participants that had both high levels of CRF and low levels of negative emotion, there was a 63% lower mortality risk.
These associations were present across all age groups and both genders. They persisted after adjusting for the presence of underlying diseases and the impact of positive emotion. Interestingly, high levels of positive emotion were not associated with mortality.
What Do We Make of This?
Ortega’s study suggests that low levels of negative emotion and high levels of cardiorespiratory fitness are independent predictors of long-term survival. What is more, these two parameters exerted a strong combined effect such that participants having both low-level negative emotion and high CRF experienced a 63% lower mortality risk than those with high negative emotion and low CRF.
This study should be considered in light of several limitations, as noted by the authors. For example, although they controlled for many risk factors for premature mortality, it may be that uncontrolled factors like dietary habits could also have played a role. These data were not available to Ortega’s group.
In addition, nearly 98% of the ACLS participants were well-educated, white, and in middle or high socioeconomic strata. It remains to be determined whether these findings will hold up in populations with more varied ethnicity and socioeconomic status. Also, the ACLS provided only a baseline assessment of negative and positive emotion. Although the authors cite previous studies suggesting that measures of psychological well-being remain stable over time, this assertion doesn’t necessarily jive with my anecdotal experiences (!).
Finally, the beneficial effect of low-level negative emotion on survival was seen only in participants with high levels of cardiovascular fitness. It did not impact those with low or moderate CRF levels…a strange, inexplicable finding that bears further scrutiny.
These limitations mean it’s unwise to recommend at this time that health professionals should routinely assess psychological health of their patients during, say, an annual physical examination, or that providers should intervene to reduce negative emotions (if that’s possible) in addition to encouraging increased physical activity. That said, the current study suggests a lot is at stake. If the findings do hold up in follow-up investigations, we might well have another compelling way to help people maintain health.
It’s worth mentioning in closing that Ortega’s group found only a modest correlation between positive and negative emotion scores: people with high levels of positive emotion do not necessarily have low levels of negative emotion, and vice versa. The group concluded that positive and negative emotion are distinct from each other and can impact survival in their own, unique ways.