In contrast to the well-established scientific evidence linking negative emotional states (e.g., depression, anxiety, or anger) to increased risk for cardiovascular disease, much less is known about the association between positive emotional states (e.g., laughter, happiness) and cardiovascular health. We determined the effects of mirthful laughter, elicited by watching comic movies, on endothelial function and central artery compliance. Seventeen apparently healthy adults (23 to 42 years of age) watched 30 minutes of a comedy or a documentary (control) on separate days (crossover design). Heart rate and blood pressure increased significantly while watching the comedy, whereas no such changes were seen while watching the documentary. Ischemia-induced brachial artery flow-mediated vasodilation (by B-mode ultrasound imaging) increased significantly after watching the comedy (17%) and decreased with watching the documentary (−15%). Carotid arterial compliance (by simultaneous application of ultrasound imaging and applanation tonometry) increased (10%) significantly immediately after watching the comedy and returned to baseline 24 hours after the watching, whereas it did not change significantly throughout the documentary condition. Comedy-induced changes in arterial compliance were significantly associated with baseline flow-mediated dilation (r = 0.63). These results suggest that mirthful laughter elicited by comic movies induces beneficial impact on vascular function.
Not much is known about the association between positive emotional state (e.g., laughter, happiness) and cardiovascular health. The primary purpose of the present study was to determine the effect of mirthful laughter, elicited by watching comedy, on vascular function as determined by arterial stiffness and flow-mediated dilatation (FMD). Watching of a documentary was used as a control condition. In addition, to gain insight into the magnitude of cardiovascular changes during mirthful laughter, heart rate and blood pressure were continuously monitored using a beat-to-beat blood pressure device.
Methods
Seventeen sedentary or recreationally active adults (12 men and 5 women) 23 to 41 years of age (mean 26 ± 1 years) were studied. Participants were apparently healthy, normotensive, nonobese (body mass index 23.0 ± 0.5 kg/m 2 ), nonmedicated, nonsmokers, and free of overt cardiovascular disease ( Table 1 ). Susceptibility of subjects to laugh was evaluated using a cheerfulness questionnaire. Candidates who marked “strongly disagree” on the questions “Everyday life often gives me the occasion to laugh” and “I like to laugh and do it often” were excluded. This was done to ensure that watching a comedy would elicit mirthful laughter. The study was reviewed and approved by the institutional review board. All subjects gave their informed consent to participate.
| Variables | Session | Baseline | After 5 Minutes | After 30 Minutes | After 24 Hours |
|---|---|---|---|---|---|
| Heart rate (beats/min) | documentary | 51 ± 3 | 51 ± 4 | 53 ± 4 | 52 ± 3 |
| comedy | 54 ± 2 | 56 ± 2 | 55 ± 2 | 54 ± 2 | |
| Systolic blood pressure (mm Hg) | documentary | 114 ± 3 | 113 ± 3 | 112 ± 3 | 112 ± 3 |
| comedy | 112 ± 2 | 112 ± 2 | 110 ± 2 | 111 ± 2 | |
| Diastolic blood pressure (mm Hg) | documentary | 60 ± 2 | 59 ± 2 | 58 ± 2 | 59 ± 2 |
| comedy | 59 ± 2 | 60 ± 2 | 58 ± 2 | 59 ± 2 | |
| Mean blood pressure (mm Hg) | documentary | 78 ± 2 | 77 ± 2 | 77 ± 2 | 77 ± 2 |
| comedy | 77 ± 2 | 77 ± 2 | 75 ± 2 | 76 ± 2 | |
| Pulse pressure (mm Hg) | documentary | 54 ± 3 | 54 ± 3 | 55 ± 3 | 54 ± 3 |
| comedy | 52 ± 2 | 52 ± 2 | 52 ± 2 | 53 ± 2 |
Participants were required to fast and abstain from caffeinated beverages for ≥4 hours before experiments. Participants were instructed not to engage in any strenuous physical activity and drink alcohol for 24 hours before the study. In addition, testing was initiated at the same time of day for each subject throughout the study period to avoid potential diurnal variations. After 15 minutes of rest in a supine position, baseline measurements of heart rate, blood pressure, and vascular function were performed. Subsequently, each subject watched 30 minutes of a comedy or documentary from a digital video disk (DVD; crossover design) in the laboratory room alone. Because sense of humor differs, each subject selected a favorite comedy program from the laboratory DVD collection that includes stand-up comedy programs featuring Jerry Seinfeld, Ellen Degeneres, Bill Cosby, so on. Otherwise, subjects brought their favorite comedy programs. In the documentary session, each subject chose a documentary from the laboratory DVD collection (e.g., economy, history, natural science, so on).
Brachial blood pressure was measured in triplicate from the right arm in a supine position with an automated oscillometric device (HEM-907XL, OMRON Healthcare, Vernon Hills, Illinois). Throughout viewing a movie, beat-to-beat finger blood pressure was continuously recorded with a photoplethysmograph (Portapres, TNO TPD Biomedical Instruments, Amsterdam, The Netherlands) and personal computing software (BeatScope 1.0, TNO TPD Biomedical Instruments, Amsterdam, The Netherlands).
Carotid artery compliance was obtained with a combination of ultrasound imaging of the common carotid artery (by B-mode ultrasound [iE 33, Philips, Bothell, Washington] equipped with a 15-MHz linear array transducer) and recording of contralateral carotid arterial pressure (by applanation tonometry; VP-2000, Colin Medical, San Antonio, Texas), as previously described. All scans were performed by the same investigator who was blinded to the order of sessions. Day-to-day coefficient of variation for arterial compliance measurements was 5 ± 2%. Carotid arterial augmentation index, an index of arterial wave reflection that is influenced by arterial stiffness, was also obtained with arterial applanation tonometry as previously described.
Brachial artery FMD measurements were performed according to an established procedure. A longitudinal image of the brachial artery was acquired 5 to 10 cm proximal to the antecubital fossa of the left arm using the ultrasound machine equipped with the compact linear array transducer and a customized transducer-holding device. The location of the transducer was clearly marked with a permanent marker to ensure measurement at the same location throughout testing. Brachial artery diameter was continuously monitored until 90 seconds after blood reperfusion and analyzed using image analysis software (Brachial Analyzer, Medical Imaging Applications, Coralville, Iowa). The same investigator, who was blinded to experimental sessions, performed all image analyses.
A stretch-sensitive strain gauge (Pneumotrace II, UFI, Morro Bay, California) was wrapped around a subject’s chest to quantify the number of laughs while watching the documentary and the comedy. The Pneumotrace analog signal was converted to a digital signal (WinDaq, DATAQ Instruments, Akron, Ohio) and recorded simultaneously on a computer for later analysis.
The Positive and Negative Affect Schedule score, a 20-item questionnaire with positive and negative affect subscales, was used to assess changes in mental and mood states.
Analysis of variance and multivariate analysis of variance with Fischer’s post hoc test were performed to compare mean values. Paired t test was applied to compare the number of laughs from the subjects. Wilcoxon matched-pairs test was used to evaluate changes in questionnaire-based psychological scales between before and after movie sessions. Pearson correlations and Spearman rank-order correlations were applied to determine relations.
Results
Number of laughs, as estimated by irregularity in respiration patterns, increased significantly while watching the comedy (97 ± 13 times), whereas watching the documentary did not disturb respiratory patterns significantly (5 ± 1 times). No significant correlations were observed between changes in vascular functions and number of laughs.
Watching comedy did not elicit significant changes in positive (16.8 ± 1.2 vs 17.3 ± 1.3) or negative (10.7 ± 0.3 vs 10.5 ± 0.2) mood scores. Watching a documentary significantly decreased positive mood (18.5 ± 1.3 vs 16.5 ± 1.5) but did not affect negative mood (10.8 ± 0.2 vs 10.9 ± 0.3). No significant correlations were observed between changes in vascular functions and positive or negative mood state.
While watching a documentary, heart rate and systolic blood pressure did not change significantly, but diastolic blood pressure increased slightly but significantly for the last 20 minutes ( Figure 1 ). While watching a comedy, heart rate increased significantly in the initial 20 minutes, and systolic and diastolic blood pressures remained increased (p <0.05) throughout the movie-watching session. Hear rate and blood pressure returned to baseline levels after watching the DVD.
Heart rate and brachial blood pressure did not change significantly throughout the protocol in either group ( Table 1 ). There were no significant differences in diastolic brachial artery diameters and FMD (documentary 8.4 ± 0.5%, comedy 8.6 ± 0.9%) at baseline between sessions. Brachial artery diameter did not change significantly throughout the protocol in the comedy or documentary sessions. FMD increased significantly 5 minutes after watching a comedy and remained increased (+12%) until 24 hours after watching ( Figure 2 ). While watching a documentary, FMD decreased, gradually reaching significance at 30 minutes after watching a movie, and returned to baseline at 24 hours.
