Julia K. Boehm

Who they are

Boehm is a health psychologist whose research concerns positive psychological wellbeing and cardiovascular health. Her 2018 paper in Circulation Research is the meta-analytic test of the behavioural explanation for why optimists appear to live longer, and it is unusual in being conducted by researchers who take the association seriously and still reporting the pathway as thin.

The samples are not small. The physical activity meta-analysis pooled 34 effect sizes across 90,845 participants, diet 15 effect sizes across 47,931, and cigarette smoking 15 effect sizes across 15,052, from PubMed and PsycINFO to November 2017, with random-effects models. The findings, in the abstract's own words, suggested that more optimistic individuals tended to engage in healthier behaviours compared with less optimistic individuals, but effect sizes were modest: 0.07 for activity, 0.12 for diet and 0.07 for smoking.

Then the quality grading, which is hers and not ours. Most evidence was cross-sectional, at 53 per cent or more of effect sizes, and most did not consider sociodemographic characteristics as potential confounders, with fewer than 27 per cent considering psychological distress. The abstract concludes that optimism is associated with healthier behaviours that protect against cardiovascular disease, although most evidence was relatively low quality. Her team also states the open question directly: it is unclear whether optimism temporally precedes health behaviours or whether the relationship is because of shared common causes.

Why this matters for the rest of the literature is arithmetic. Formal mediation in 159,255 women puts the lifestyle-mediated share of the optimism and life-span association at 24 per cent, and model comparison in the nurses' cohort puts it at roughly two fifths. Those are shares of a pathway whose component correlations, measured here, sit between 0.07 and 0.12 and are mostly cross-sectional. A pathway that mediates a quarter of an effect while correlating at 0.07 with its own components is a thin thread to hang a mechanism on, and the article places this paper immediately after the mediation numbers for that reason.

One structural observation, which is about the size of the field rather than about anybody's conduct. Boehm's paper shares authors with the cohort papers it bears on: Hayami Koga is third author here and led the 2022 cohort study, and Laura Kubzansky is last author on this paper, on the 2022 cohort paper and on the 2019 nurses' paper. Specialised fields look like this, and it does mean the evidence is less independent than a citation count suggests.

Our read of this paper is its abstract, read in full at a repository that prints it entire. The full text was not reached, and nothing beyond the abstract's own figures and wording is attributed to it here.

Key papers

Boehm is an academic psychologist whose relevant output is journal articles rather than books.

Boehm, J. K., Chen, Y., Koga, H., Mathur, M. B., Vie, L. L., & Kubzansky, L. D. (2018). "Is Optimism Associated With Healthier Cardiovascular-Related Behavior? Meta-Analyses of 3 Health Behaviors." Circulation Research 122(8), 1119-1134, doi:10.1161/CIRCRESAHA.117.310828. Abstract read in full for this article; full text not read.

Key ideas

Optimism is associated with healthier physical activity, diet and smoking behaviour, at correlations of 0.07, 0.12 and 0.07.

Most of that evidence is cross-sectional, and most of it does not adjust for socio-economic position or psychological distress.

The quality grading, relatively low quality, is the authors' own published judgement of their own field's evidence.

Whether optimism precedes health behaviour or shares a common cause with it is unresolved, and her team says so.

A behavioural pathway this weak sets a ceiling on how much of the longevity association behaviour can plausibly carry, whatever the mediation percentage says.

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