Effects of Acute Exercise on Anxiety Ratings in Patients With Coronary Heart Disease and Elevated Anxiety

Abstract

Purpose:

To explore individual differences in state anxiety following a single, acute bout of aerobic exercise among anxious patients with diagnosed coronary heart disease (CHD).

Methods:

One hundred eighteen CHD patients with elevated symptoms of anxiety enrolled in the UNderstanding the Benefits of Exercise and Escitalopram in Anxious Patients WIth coroNary Heart Disease (UNWIND) clinical trial rated their level of anxiety using a 100-mm visual analog scale before and after a symptom-limited exercise treadmill test. A number of exercise (eg, peak oxygen uptake, exercise duration, maximum heart rate, anaerobic threshold) and psychological variables were examined as potential predictors of exercise response. Changes in anxiety and their association with psychological variables were examined using general linear models.

Results:

Fifty patients (42%) rated a reduction in anxiety relative to their pre-exercise ratings following the exercise treadmill test. While a number of factors were examined, the only factor that distinguished those individuals who reported a reduction in anxiety symptoms compared with those who either remained the same or actually reported an increase in anxiety was a higher pre-exercise visual analog scale anxiety rating. No differences were observed as a function of sex, severity of trait anxiety, the presence of an anxiety disorder, exercise test duration, or age.

Conclusions:

Although many variables were examined, only higher baseline anxiety distinguished those who showed a reduction in their visual analog scale ratings from those whose anxiety remained the same or got worse. The extent to which the response to acute exercise predicts the anxiolytic effects of chronic exercise needs further study.

Over the past two decades, there has been growing evidence for the mental health benefits of physical exercise. A number of studies have documented improvements in depression^1–4 and, to a lesser extent, in anxiety^5,6 following chronic aerobic exercise or resistance training. Anxiety is common in patients with coronary heart disease (CHD)^7,8 and may have a bidirectional relationship as being both a cause and consequence of CHD events.^9,10 Furthermore, anxiety may serve as a deterrent to exercise participation and has been associated with premature dropout from cardiac rehabilitation programs.^11–14

The mechanisms responsible for the purported benefits of exercise are uncertain. The physiological symptoms of anxiety (eg, tachycardia, perspiration) are also provoked by exercise and thus could be interpreted as a normal reaction to physical exercise. Another possibility is that the improvements in anxiety may result from an accumulation of short-term benefits following repeated bouts of acute exercise. Indeed, the anxiolytic effects of acute exercise have been reported in a number of observational and interventional studies.^15–18 In an early review of the literature, Petruzzello and colleagues¹⁹ performed a meta-analysis of the chronic and acute effects of exercise on anxiety. They identified 104 studies and >3000 participants and concluded that acute bouts of aerobic exercise, but not anaerobic exercise, reduced state anxiety.¹⁹ In a subsequent meta-analysis of 36 randomized clinical trials involving >1233 participants, Ensari and colleagues²⁰ reported an overall effect size of Hedge’s g = 0.16, which was considered small but statistically significant. They noted that approximately half of study participants experienced a reduction in anxiety symptoms following an acute exercise session. There was significant heterogeneity across studies, however, with such factors as exercise modality and intensity, age, sex, and health status affecting exercise-related reductions in anxiety.²⁰

In this report, we sought to determine what factors might moderate the acute effects of exercise on symptoms of anxiety. Specifically, we examined the acute effects of a single bout of maximal exercise on self-ratings of anxiety among a sample of patients with CHD and elevated symptoms of anxiety. All participants underwent a symptom-limited cardiopulmonary exercise test (CPX), with self-ratings of anxiety obtained immediately before and following completion of the test. To identify potential moderators of exercise-related changes in anxiety, we examined characteristics of those individuals who reported a reduction in anxiety compared with those whose anxiety remained the same or worsened following exercise.

METHODS

All participants were enrolled in the UNderstanding the Benefits of Exercise and Escitalopram in Anxious Patients WIth coroNary Heart Disease (UNWIND) trial.²¹ Participants first underwent medical and psychiatric screening on the same day. They were considered eligible if they had stable CHD (ie, revascularization procedure, >70% blockage determined by coronary angiography, myocardial infarction, etc) and had significant anxiety defined as either obtaining a score of ≥8 on the anxiety component of the Hospital Anxiety and Depression Scale (HADS-A)²² or having a diagnosed anxiety disorder as determined by a trained clinical psychologist. Furthermore, participants were not taking any psychotropic medication that could alter their mood. The psychological screening procedures were completed within 1 wk prior to the exercise testing described later. Participants also had to be sedentary (exercising ≤1 d/wk) but able to exercise. The study was approved by the Institutional Review Board at Duke University Medical Center, where all assessments were performed. Written informed consent was obtained from all participants before their participation.

PSYCHIATRIC ASSESSMENT

All participants were assessed by a clinical psychologist who administered modules from the Structured Clinical Interview for DSM-V Disorders (SCID)²³ and the 14-item Hamilton Anxiety Rating Scale (HAM-A).²⁴ In addition, participants completed a series of self-report instruments including the State-Trait Anxiety Inventory (STAI-Trait)²⁵ and the Hospital Anxiety and Depression Scale (HADS).²²

PRE-POST CPX ANXIETY ASSESSMENT

The visual analog scale (VAS) has been shown to be a valid and reliable instrument to evaluate acute changes in acute anxiety.²⁶ Anxiety was assessed using a 100-mm VAS anchored by “0” (“completely calm and relaxed”) on one end and “100” (“as anxious and tense as I’ve ever been”) on the other. Participants completed the VAS in a seated position immediately before beginning a symptom-limited CPX and again approximately 8 min following the completion of the test, once their blood pressure and heart rate returned to a resting state. Upon completing the post-exercise VAS rating, we also provided the participants with their initial pre-CPX rating and then asked them to rate their current anxiety level viewing their previous pre-exercise rating.

ACUTE EXERCISE PROTOCOL

Participants completed a symptom-limited, graded CPX following the Duke-Wake Forest protocol²⁷ in which treadmill speed and incline were increased at a rate of 1 metabolic equivalent/min. Peak oxygen uptake $(\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}})$ was determined by the highest 15-sec average value. Patients exercised to exhaustion or other standard clinical end points (eg, abnormal blood pressure response, 1-mm ST-segment depression, chest pain symptoms) under continuous electrocardiographic monitoring; expired gas was collected by mouthpiece for quantification of minute ventilation, oxygen uptake, and carbon dioxide production with a TrueOne 2400 (Parvo Medics) metabolic cart.

STATISTICAL ANALYSIS

Data were analyzed using SAS 9.4. To compare individuals who showed, or did not show, a decrease in anxiety following the CPX, we first characterized group differences using χ² test for categorical variables and general linear models for continuous outcomes. To examine changes in anxiety, we also examined a multivariate linear regression model in which factors previously postulated to impact VAS ratings were incorporated, including pre-exercise VAS levels, age, gender, and ventilatory threshold (VT) time. Model assumptions regarding additivity, linearity, and normality of residuals were evaluated and found to be acceptable prior to analysis.

RESULTS

Background and clinical characteristics of the sample with VAS ratings are shown in the Table. Patients (n = 118) with documented CHD and elevated symptoms of anxiety were recruited. Participants were primarily White (70%) and male (72%), with an average age of 65 yr, and a history of diagnosed CHD, including myocardial infarction (57%) and coronary artery bypass grafting (24%). In addition, 93 participants (79%) were diagnosed with an anxiety disorder by a clinical psychologist.

Table.

Background and Clinical Characteristics Among Participants Showing Increase or Decrease in VAS Anxiety Ratings^a

Variable	Increase (n = 68)	Decrease (n = 50)	P Value
Pre-exercise VAS rating	19 ± 14	33 ± 21	<.001
BDI-II	16 ± 8	16 ± 8	.917
STAI-T	42 ± 7	42 ± 7	.678
Age, yr	64 ± 9	65 ± 10	.281
Ventilatory threshold time, min	4.4 ± 1.5	4.1 ± 1.4	.237
Exercise duration, min	8.1 ± 2.4	7.3 ± 2.6	.195
Sex (male)	51 (75)	34 (68)	.403
Race (White)	47 (69)	36 (72)	.904
Prior MI	39 (57)	29 (58)	.944
Prior CABG	16 (23)	12 (24)	.953
Past smoking	33 (49)	23 (46)	.786
Hypertension	50 (74)	37 (74)	.954
Diabetes	24 (35)	20 (40)	.604

Abbreviations: BDI-II, Beck Depression Inventory-II; CABG, coronary artery bypass grafting; MI, myocardial infarction; STAI-T, State-Trait Anxiety Inventory-Trait; VAS, visual analog scale.

^aData are presented as mean ± SD or n (%).

Overall, participants averaged 7.8 ± 2.5 min with an average $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$ of 18.9 ± 5.8 mL/kg/min on the CPX. Males achieved a higher $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$ (20.7 [19.5–21.9] mL/kg/min) than females (14.2 [12.9–15.6] mL/kg/min) (P < .001) and also had longer treadmill duration times (males = 8.5 [8.0–9.0] min; females = 6.0 [5.3–6.7] min) (P < .001).

The average baseline VAS score was 24.8 ± 18.3 mm, while the average post-exercise score was 25.5 ± 18.7 mm. Pre-CPX VAS ratings were negatively correlated with exercise duration (r = −0.024, P = .010) and exercise time beyond their VT (r = −0.024, P = .010), but pre-CPX VAS ratings were not significantly correlated with the time patients reached their VT (r = −0.014, P = .132).

Fifty participants (42%) indicated a decrease in anxiety, whereas 68 participants (58%) reported increased VAS anxiety ratings. Changes in VAS ratings from pre-to-post-exercise revealed notable individual variations, with an average increase of 2.0 ± 20.9 mm. The average reduction in VAS ratings for those patients who showed a post-CPX reduction in anxiety was 15.8 ± 14.6 mm, and the average increase in VAS ratings for those patients who showed an increase in anxiety was 15.0 ± 14.1 mm (Figure). Comparison of characteristics of individuals who reported a reduction in anxiety with those who showed an increase or no change revealed that only baseline VAS ratings distinguished the 2 groups (P < .001), with higher baseline VAS scores associated with greater reductions in VAS scores after exercise. We also compared the independent post-CPX VAS ratings (ie, those ratings made immediately following exercise without knowledge of their pre-CPX ratings) with the relative ratings (ie, ratings made after the participant was provided with his or her pre-exercise ratings). Results were highly related (P < .001), with 86% of participants classified as having shown a reduction in anxiety post-exercise also indicating that their anxiety was lower after exercise when provided with their pre-exercise values. Only five participants who initially reported a reduction in VAS scores indicated that they did not experience a reduction in anxiety after they were presented with their initial VAS ratings.

Figure.

Mean VAS scores (± SE) are displayed pre- and post-CPX for both groups. Comparison of individuals who showed decreased anxiety post-CPX (n = 50) with those who showed increased anxiety post-CPX (n = 68). Participants who showed decreased anxiety had higher baseline VAS scores than those who showed increased anxiety (P < .001). Following acute exercise, those with higher VAS ratings reported less anxiety than those with lower baseline VAS ratings. Abbreviations: CPX, cardiopulmonary exercise test; VAS, visual analog scale.

DISCUSSION

Our findings indicate that a single bout of maximal aerobic exercise can produce significant reductions in self-reported anxiety in a significant subgroup of CHD patients with high anxiety, including some patients with a diagnosed anxiety disorder. These findings are consistent with several prior studies that showed that acute exercise may have anxiolytic effects in healthy adults.^17,28,29 In this study, 42% of participants indicated a decrease in anxiety after a symptom-limited CPX. The proportion of patients reporting a decrease in anxiety is consistent with data reported by Ensari and colleagues,²⁰ in which they observed that 54% of participants reported a reduction in state anxiety following an acute bout of exercise.

In an effort to identify characteristics that might distinguish those who showed reduced anxiety compared with those who showed no change or an increase in anxiety, we found that those patients with higher pre-exercise VAS scores, compared with those with lower scores, showed greater reductions in anxiety post-exercise. These data support the findings by Lucibello and colleagues,³⁰ who concluded that participants aged 18–30 yr exercising ≤1 d/wk with higher baseline anxiety levels experienced a greater decrease in anxiety symptoms after an acute exercise session than those starting with lower anxiety levels.³⁰ Furthermore, the present results extend these findings by showing that a significant subgroup of older adults with CHD and high pre-exercise state anxiety may also report a reduction in anxiety after an acute bout of exercise.

In addition to heightened pre-exercise anxiety, several other factors have been considered as possible modifiers of the acute effects of exercise on anxiety. A number of studies have reported sex differences in response to exercise. For example, Herring et al³¹ found that females were more likely to show a significant reduction in state anxiety than males after 30 min of exercise at 65–85% heart rate reserve. McDowell and colleagues¹⁸ reported a greater improvement in mood, including state anxiety, among females who completed a 30-min intense exercise session than among males who completed the same session. However, the improvement in state anxiety for the females was not significant (d = 0.51, 95% CI: −0.07 to 1.08).¹⁰ In this study, we found that on average females exercised for less time than males and had lower $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$ but did not show greater reductions in VAS scores before or after completion of maximal exercise compared with males.

Intensity of exercise is another factor that may influence anxiety levels following exercise. In a comparison of low-intensity exercise (~57% $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$) and high-intensity exercise (~81% $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$) with a resting control condition in eight male obese adolescents, Lofrano-Prado and colleagues³² reported that state and trait anxiety were increased following exercise in both exercise conditions and that the higher-intensity session yielded higher average anxiety scores compared with both the low intensity and control conditions. The authors concluded that the higher-intensity session resulted in higher post-exercise anxiety than the lower-intensity session, suggesting that there may be an inflection point, such as the anaerobic threshold, which may determine the extent to which a bout of exercise affects mood.³²

Ekkekakis and colleagues³³ reviewed 33 publications that examined the relationship between exercise intensity and pleasure, with >1000 total participants ranging from 12–68 yr of age. They concluded that the VT may represent an inflection point, in which exercising above this point yields less enjoyment, while exercising at sub-maximal levels may elicit greater feelings of pleasure. Ekkekakis et al³³ suggest that sedentary or overweight individuals tend to report lower scores of pleasure sooner, including during a CPX, compared with physically active individuals. We found that those who showed a reduction in VAS scores did not differ from those who reported increased VAS scores in their VT or $\stackrel{.}{\text{V}}{\text{o}}_{2\text{peak}}$; however, higher pre-exercise anxiety was associated with shorter exercise duration and less time spent exercising beyond their VT, which may have contributed to their lower VAS ratings.

Older age also has been suggested as potentially enhancing the benefits of acute exercise on anxiety. In their analysis of 36 studies, Ensari et al²⁰ concluded that participants ≥25 yrs have a greater benefit from an acute exercise session than those who are younger. However, many studies in this area have relied on college students and younger adults, with relatively few studies with truly “older” individuals. Most would not consider 25 yr of age to be old, and there is no obvious explanation of why older adults would benefit more from acute exercise than their younger counterparts. Indeed, in our study of older adults, we found that age was not a predictor of anxiety response to acute exercise.

LIMITATIONS

Because all patients were instructed to exercise to their maximum and we did not assess anxiety at submaximal workloads, it is possible that more participants may have experienced a reduction in anxiety if they had been assessed at submaximal workloads. It is possible that as exercise progressed, they may have become more anxious. Because several studies have shown that some individuals benefit more from a lower-intensity exercise session, it is possible that the high level of exercise intensity may have attenuated the anxiolytic effects of exercise for many participants.^32–34 In addition, because patients knew that exercise testing may elicit cardiac abnormalities, it is possible that some patients may have been more apprehensive about developing potential symptoms at the start of the test. If these patients did not experience symptoms during exercise, their heightened anxiety may have been reduced. All patients were sedentary and reported high levels of anxiety, which may limit the generalizability of our findings. Importantly, regression to the mean is another potential explanation for our finding that individuals with higher pre-CPX anxiety levels had greater VAS reductions than those with lower pre-CPX anxiety. We cannot rule out regression to the mean as an explanation for our findings; however, the fact that participants were consistently classified using two different methods as either showing a decrease or increase in anxiety following CPX testing suggests that their response to acute exercise was reliable. Finally, the clinical significance of these findings remains uncertain. While heightened anxiety is undoubtedly highly prevalent among CHD patients, is often a barrier to exercise participation, and may attenuate the antidepressant effects of exercise,³⁵ only half of our sample reported anxiolytic benefits from a single bout of maximal exercise. It is not clear whether those individuals who showed a reduction in anxiety after acute exercise will maintain benefits over time with chronic exercise. For those individuals who do not experience reduced anxiety with exercise, other strategies to reduce anxiety may be needed.

CONCLUSIONS

Results from this study indicate that a significant subset of patients with stable CHD and high anxiety showed significant reductions in self-reported anxiety after completion of a single bout of maximal aerobic exercise. Although many variables were examined, only higher baseline anxiety distinguished those who showed a reduction in their VAS scores from those whose anxiety remained the same or got worse. To our knowledge, this is the first study to have examined the effects of acute exercise on anxiety in anxious CHD patients. However, our sample was small and our study is in need of replication. Future research should examine how different exercise intensities might differentially affect anxiety during exercise. The extent to which the acute anxiolytic effects of exercise might predict the accumulated effects of chronic exercise also needs further study.