- Several studies have found an association between personality, immune system biomarkers, and long-term health outcomes.
- The immune system-related biomarker interleukin 6 (IL-6) and the acute phase protein C-reactive protein (CRP) are an integral part of the immune response, playing both pro- and anti-inflammatory roles.
- Conscientiousness — a tendency to be responsible, organized, and capable of self-control — is one personality trait linked to a lower risk of mortality
- In a new study, researchers found that those with higher conscientiousness as a personality trait also had lower IL-6 levels and a reduced risk of death.
- This finding is significant because it establishes a biomarker as the direct link in a pathway between a personality trait and the risk of mortality.
Personality traits make up how a person navigates through life, with some characteristics having a more positive effect than others.
Aside from their psychological impact on a person’s life, studies show that these traits are also associated with long-term health outcomes and mortality.
According to Dr. Páraic Ó Súilleabháin, of the Department of Psychology and the Health Research Institute at the University of Limerick: “Our personality is critically important throughout our lives, from early stages in our development to the accumulation of the impact of how we think, feel, and behave across our lives and in the years preceding our death. It is also becoming increasingly apparent how important personality actually is for our long-term health and resulting longevity.”
Many studies link conscientiousness to beneficial health-related behaviors, including lower alcohol consumption, less smoking, healthier eating habits, and more physical activity.
Additionally, a meta-analysis found that those who scored the lowest in this trait had a risk of death that was 1.4 times higher than that of those who scored highly, even after adjusting for health behaviors, marital status, and education.
Another study found that conscientiousness is also linked to lower IL-6 levels circulating the body, which researchers have shown to be a contributing factor in long-term health outcomes and risk of premature mortality.
Although scientists understand that conscientiousness tends to promote longevity, it is unknown how this happens.
Research that the University of Limerick led in partnership with West Virginia University, Humboldt University, and Florida State University sought to uncover how this personality trait affects CRP and IL-6 and what overall effect it has on longevity.
The results of the study appear in the journal Brain, Behavior, and Immunity.
Working with 957 adult participants from the Midlife in the United States (MIDUS) study, researchers investigated the pathways between personality traits, IL-6 and CRP, and mortality risk.
The team assessed personality traits using the Midlife Development Inventory (MIDI) Personality Scales, where participants indicated their tendency toward specific personality characteristics by answering questions on a four-point Likert scale.
The researchers then took blood samples from the participants and measured their levels of CRP and IL-6 inflammatory biomarkers. They also noted characteristics and variables with the potential to affect the study outcomes, including age, sex, race, education, smoking status, chronic conditions, medications, and physical activity.
The research team found that the participants who had higher conscientiousness scores also had a lower risk of mortality. Data showed that each standard deviation of higher conscientiousness was associated with a 35% lower risk of death.
However, after fully adjusting the model, IL-6 accounted for 18% of this association. The investigators also found no evidence that CRP acted as a direct mediator between conscientiousness and mortality risk.
After the research team adjusted the findings to take sociodemographic variables into account, other personality traits — including extraversion, openness, neuroticism, and agreeableness — did not show the same association as conscientiousness.
This discovery suggests that higher conscientiousness and its potential to lower IL-6 levels in the body may lead to a longer lifespan.
“We found that part of the reason why people who score higher on the personality trait of conscientiousness live longer is as a result of their immune system, specifically due to lower levels of a biological marker called interleukin-6. There are likely further biological mechanisms that are yet to be discovered, which will give a clearer picture of all the different ways that our personalities are so critical to our long-term health.”
– Dr. Ó Súilleabháin
The researchers note a few limitations of their research, including the need to examine other potentially relevant pro- and anti-inflammatory biomarkers further.
They also note that a more comprehensive personality scale that considers underlying personality facets could better tease out the nuances between biological markers and conscientiousness.
Additionally, looking at cause-specific mortality in a larger group of participants could help determine whether any of those causes are responsible for the associations that this study has uncovered.
Despite the limitations, Dr. Ó Súilleabháin and his colleagues believe that these findings are significant because they show, for the first time, that underlying biological markers link directly to personality and mortality risk.
If researchers can replicate these results in future studies, the information could provide new ways to improve personality-related health interventions.