What moderates salivary markers of inflammation reactivity to stress? A descriptive report and meta-regression

As the assessment of salivary markers of inflammation gains popularity in stress research, understanding factors that influence these markers' reactivity to stress is important. A recent meta-analysis synthesized literature on changes in salivary markers of inflammation in response to acute stressors in adults. As a supplement to this, we present pre-registered moderator analyses of salivary markers of inflammation responses to acute stress. Analyses included data from 27 studies (35 unique study samples). Outcomes were Cohen's d effect sizes for salivary biomarkers interleukin-1 beta (IL-1β), IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α), from pre- to post-stress. Moderators included: college education levels of the study sample; percent of the study sample that identified as African-American; body mass index (BMI); use of a resting baseline saliva sample; and use of a social evaluative stressor. Descriptive results on saliva sample timing were also examined. Biomarkers peaked 0-60 minutes after the end of the stressor. Before removing influential outliers, no moderators of salivary inflammation reactivity emerged, though not all moderators could be tested due to missing data. After removing one influential outlier study, higher study sample average BMI was associated with greater salivary IL-1β reactivity to stress (b = 0.41, p=.007). For every 1-unit increase in study sample average BMI, effect sizes for IL-1β increased by 0.41 units. These findings suggest BMI may be important to examine when assessing salivary markers of inflammation in response to stress. As this field expands, it is important to replicate these results and consider the role of other moderators of salivary markers of inflammation reactivity to stress.