Slow- Versus Normal-Paced Breathing During an Emotional Task: Limited Evidence for Greater RMSSD Change or State-Affect Benefits

Slow-paced breathing (SPB) is widely promoted for stress regulation, but its incremental benefit over an active paced-breathing control across age groups remains uncertain. We compared SPB (prescribed 6 cycles/min) with normal-paced breathing (NPB; prescribed 12 cycles/min) during an emotional picture-rating task in 82 younger and 84 older adults. Outcomes were baseline-to-task changes in heart rate variability indexed by the root mean square of successive differences (RMSSD) and mean heart rate, and pre–post changes in state anxiety and affect. The primary RMSSD analysis included 162 participants after the ± 3 median absolute deviation exclusion rule. RMSSD was higher during the task than during the preceding baseline in both protocols. The primary Time × Breathing condition interaction did not establish a larger change under SPB, β = 0.090, 95% CI [− 0.022, 0.203], p = .116, and was sensitive to outlier handling. A secondary task-period contrast showed higher RMSSD under SPB than NPB (ratio = 1.23, p = .009). Mean heart rate decreased without a reliable protocol difference in change. State anxiety and affect showed no robust advantage of SPB. Mixed-model sensitivity analyses likewise did not establish overall protocol differences in change. No reliable age moderation was detected. Respiration was not recorded directly, and adherence to 6 cycles/min or comparable respiratory exposure across ages could not be verified. Overall, the primary analyses provided no reliable evidence of a greater RMSSD change or of an acute state-affect benefit under SPB in this task context; they neither establish equivalence nor isolate the effect of breathing frequency.