DescriptionPersonality and inflammation in older people Extended abstract: There is an increasing amount of evidence that individual differences in stable personality traits relate to various health outcomes, including mortality. Much of the relevant research has been based on (often self-reported) broad health conditions such as presence of a cardiovascular disease or diabetes, general illness burden, or self-reported general health status. More recently, researchers have started to investigate whether and how personality traits relate to more specific and objectively-determined aspects of physical health. One such specific and objectively-measureable health variable is inflammation as indexed using various inflammatory biomarkers. In the short term, inflammation is an adaptive physiological response of the organism, helping it to cope with damage. In contrast, chronic inflammation—an increase in which characterizes older populations in particular—has been associated with a variety of negative outcomes such as cognitive decline, diabetes, cardiovascular disease and mortality. It is likely that knowing the associations between personality traits and inflammatory markers, and potential mechanisms of these associations, may help to better understand how and along which pathways personality traits relate to physical health. To date, however, only few reports on personality-inflammation associations are available and most of them have probably been underpowered to detect the presumably small effects. Nevertheless, there appears some consistency in linking elevated levels of inflammatory markers to low conscientiousness and openness. With respect to latter, it is unknown to which degree this association may be confounded by individual differences in cognitive ability, a correlate of both inflammation and openness. In this study, cross-sectional and longitudinal associations between the Five-Factor Model’s (FFM) personality traits and several inflammatory biomarkers were investigated in two large samples of older people: the Lothian Birth Cohort 1936 (LBC1936), and the Edinburgh Type 2 Diabetes Study (ET2DS). The FFM personality traits are Emotional Stability (reverse of Neuroticism), Extraversion, Intellect (often called Openness), Agreeableness and Conscientiousness. As possible mediators or counfounders of any personality-inflammation association, emotional distress (anxious and depressive tendencies), several health-related behaviours and adverse health conditions, and socioeconomic and cognitive variables were considered. In both samples, the FFM personality traits were measured with an International Personality Item Pool based 50-item measure that quantifies people’s standing on each of the FFM personality traits using ten items. In LBC1936 (N = 1091), personality traits, acute-phase proteins C-reactive protein (CRP) and fibrinogen were measured at ages around 70 and 73 years. In addition, an inflammatory cytokine interleukin-6 (IL-6) was measured at age around 73 years. In ET2DS (N = 921), personality traits, CRP, fibrinogen and two additional inflammatory cytokines (IL-6 and tumor necrosis factor-alpha (TNFα)) were measured cross-sectionally at a mean age of 68 years. In LBC1936, high CRP levels were associated with lower conscientiousness cross-sectionally and longitudinally, and fibrinogen at age 73 was negatively related to conscientiousness at both testing occasions. The associations were attenuated to varying degrees by adjusting for anxiety and depression and childhood cognitive ability, educational attainment, occupational social class, body mass index, and disease burden (count of self-reported cardiovascular disease, stroke history, high blood pressure, diabetes, and arthritis). Controlling for health-related behaviours such as smoking, alcohol consumption and physical activity had only negligible impact on the associations. Conscientiousness at ages 70 and 73 was also related to IL-6 at age 73, with largely similar attenuation effects than appeared for CRP and fibrinogen. Intellect at age 70 was significantly negatively correlated with CRP and fibrinogen at age 73. These correlations were notably attenuated after adjusting for covariates. In ET2DS, Intellect was significantly negatively correlated with IL-6, and the correlation was strongly attenuated by adjusting for educational level, body mass index and disease burden (count of high blood pressure and histories of heart attack, angina and stroke). The personality-inflammation associations that appeared as significant were consistent with the few available previous reports, although they were small in effect size (which, of course, is typical in the area of personality epidemiology and was therefore expected). The fact that none of the relationships found in LBC1936 replicated in ET2DS may potentially be caused by the fact that ET2DS sample is not a general community sample but consists of exclusively diabetics. Diabetes is a chronic condition which is characterized by many co-morbidities and often involves ongoing medication. As a result, it is possible that the mechanisms that link personality traits to inflammatory processes in people without this chronic condition may be irrelevant for diabetics. For instance, diabetics may have to, and therefore be motivated to, monitor their health and make efforts to maintain constant health condition irrespective of their general level of conscientiousness. Taken together, this study adds to the growing body of literature which shows that personality differences between people, especially in the traits broadly summarized as conscientiousness, are related to their physical health. The personality-health associations do not only appear with self-reported health-conditions but also with objective and specific biomarkers. The present study shows that the personality-inflammation associations may be moderated by general health condition: they may appear more strongly in more healthy people, whereas in those people characterized by chronic health conditions such as diabetes the links may broke. Further investigation of personality-inflammation association on various types of samples is warranted.
|Period||9 Sep 2011|