Friday, April 17, 2015

Your friends know how long you will live.

An interesting study from Jackson et al. analyzing data from an east coast cohort of 600 people observed in the 1930s through 2013:
Although self-rated personality traits predict mortality risk, no study has examined whether one’s friends can perceive personality characteristics that predict one’s mortality risk. Moreover, it is unclear whether observers’ reports (compared with self-reports) provide better or unique information concerning the personal characteristics that result in longer and healthier lives. To test whether friends’ reports of personality predict mortality risk, we used data from a 75-year longitudinal study (the Kelly/Connolly Longitudinal Study on Personality and Aging). In that study, 600 participants were observed beginning in 1935 through 1938, when they were in their mid-20s, and continuing through 2013. Male participants seen by their friends as more conscientious and open lived longer, whereas friend-rated emotional stability and agreeableness were protective for women. Friends’ ratings were better predictors of longevity than were self-reports of personality, in part because friends’ ratings could be aggregated to provide a more reliable assessment. Our findings demonstrate the utility of observers’ reports in the study of health and provide insights concerning the pathways by which personality traits influence health.
Some details from the text of the article:
Between 1935 and 1938, 600 individuals (300 engaged heterosexual couples) began participating in the KCLS, a longitudinal study on personality and newly formed marriages. Participants were recruited through newspaper advertisements, other advertisements, and word of mouth in the state of Connecticut. The participants were primarily from middle-class backgrounds...Peer ratings were obtained from people that participants identified as knowing them well enough to provide accurate ratings; most of these friends had been in the participants’ wedding parties. Each participant named three to eight friends, and the majority of participants were rated by five friends...Self-ratings and peer ratings of personality were obtained using the 36-item Kelly Personality Rating Scale..we conducted a study to validate the PRS using more modern personality measures: the Big Five Inventory, the Iowa Personality Questionnaire, and the Mini International Personality Item Pool...The resulting five-factor solution reflected the Big Five factor structure. Extraversion was assessed with five items (e.g., quiet, popular), agreeableness with six items (e.g., courteous, sincere), conscientiousness with five items (e.g., persistent, reliable), emotional stability with four items (e.g., nervous, temperamental), and openness with four items (e.g., cultured, intelligent). Analyses indicated that the model adequately captured variation in modern Big Five composite scores...The average life span for men was 75.2 years (range = 23–98 years, SD = 15.5). The average life span for women was 81.3 years (range = 23–102 years, SD = 13.4). The 21 surviving participants had an average age of 97.2 years (SD = 2.1) in 2013.

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