How does positive affect reduce mortality? Int.J. Behav. Med. Feb.2015

Positive affect is associated with lower mortality and morbidity.Prospective studies have found that positive affect (PA) and other positive traits (e.g., optimism, hopefulness, life satisfaction, sense of humor) predicted a reliable reduction in mortality of 28 % in healthy individuals (Chida Y, Steptoe A,2008)

How does positive affect lead to less mortality? There are likely to be multiple pathways. One biological pathway is likely to be via HRV ( Heart Rate Variability= cardiac vagal tone). Greater Positive Affect is associated with high HRV and this has shown to have beneficial effects.

Andreas R. Schwerdtfeger, Peter Friedrich-Mai & Ann Kathrin S. Gerteis from Austria looked at relationship between PA and nocturnal cardiac activation.

Participants  rated various affective states several times a day via mobile electronic devices and this was related to the aggregated ratings to nocturnal cardiac activity. A small device attached to chest measured HRV and HR. Body movements were also monitored.

Results

PA ( specifically:  relaxed, content, even-tempered, calm) throughout the day was positively associated with HRV and negatively associated with HR throughout a time interval between 1 am and 5 a.m. Daily affect accounted for approximately 12–13 % of the variance in nocturnal cardiac activation.

Other studies have shown that attenuated nocturnal HRV and elevated HR is linked to  increased risk for all-cause mortality. PA experienced throughout the day might constitute a buffer against cardiac morbidity and mortality.

Previous study has  found that daily worry (a component of Negative Affect) to be accompanied by lower HRV during sleep. NA failed to show any effect in this study.

Limitations: It is possible that quality of sleep may explain the observed association. i.e. more relaxing sleep as evidenced by lower HR and higher HRV could impact affect. Poor subjective sleep quality has been found to be associated with lower ambulatory PA the next day.Physical exercise can lead to both elevated HRV and PA. Sleep and physical exercise measures are required to understand such possibilities. Directionality of association is not clear in this study.

Conclusion: Positive affect  may have beneficial effects on heart that is exerted via HRV. Mental health risk factors to morbidity and mortality are emerging topics where investigation like this adds to the evidence base.

Daily positive affect and nocturnal cardiac activation.

Schwerdtfeger AR, Friedrich-Mai P, Gerteis AK.

Int J Behav Med. 2015 Feb;22(1):132-8.

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