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Introduction: Tobacco smoking is the leading preventable cause of death globally, with nearly six million tobacco-attributable deaths each year. Approximately 17% of the New Zealand (NZ) population smoke tobacco daily. Smoking cessation in NZ is therefore an important public health challenge. Despite the proven efficacy of the various cessation approaches, long-term cessation rates are still below 25%, and new approaches are needed to increase these. Exercise has been proposed as one potential aid to smoking cessation that, if effective, could be relatively inexpensive, acceptable and easy to introduce on a wide scale. Objectives: To investigate if exercise has potential to assist with smoking cessation and the underlying psychological and physiological mechanisms explaining the relationship. Design and results: Five complementary studies were undertaken. A systematic review of studies of the acute effects of exercise on cigarette cravings, tobacco withdrawal symptoms, affect, and smoking behaviour was conducted, to explore possible psychological and physiological mechanisms in the relationship between exercise and cigarette cravings. Fifteen studies published between 2006 and 2012 were identified. Meta-analyses of the effects of exercise and passive control conditions on cigarette cravings post–cessation treatment found that exercise significantly reduced cravings on average by 2 points on a 7-point scale. The review of possible mechanisms highlighted the need for further laboratory-based research on appetite suppression, affect, and neurobiological mechanisms including cortisol, noradrenaline, adrenaline, and heart rate variability. The first empirical study was a small randomised crossover trial (n=40) that aimed to examine the effect of three different intensities of exercise on cigarette cravings, tobacco withdrawal symptoms, peripheral markers of neurobiological changes, and heart rate variability during temporary smoking abstinence. Statistically significant treatment effects were observed for cigarette cravings [desire to smoke (F[2, 91] = 7.94, p = .0007), strength of desire to smoke (F[2,98] = 5.51, p = .005)], and some tobacco withdrawal symptoms [restlessness (F[2,123] = 3.27, p = .04), hunger (F[2,103] = 6.38, p = .002), and composite mood and physical symptoms score (F[2,117] = 3.62, p = .03)]. There was a statistically significant interaction effect for noradrenaline (F[8, 72] = 2.23, p = .03), with significant differences in least square means observed between light and vigorous conditions (Least squares mean difference [SE] = 2850 [592], p <.0001). However, no statistically significant interaction or main effects for plasma cortisol, salivary cortisol, adrenaline, glucose or insulin were observed. There were statistically significant interaction effects for time and frequency domain measures of heart rate variability. A systematic review of studies of exercise interventions for smoking cessation was conducted. The review identified 20 studies published between 1985 and 2012. Metaanalyses of the effects of exercise and control conditions on point-prevalence and continuous abstinence at end of treatment, 6 months, and 12 months, revealed statistically significant differences in point-prevalence abstinence at end of treatment and 6 months, but no differences at 12 months or for continuous abstinence at any time point. Only one study found a statistically significant difference between exercise and control groups on smoking abstinence at 12 months’ follow-up. The review concluded that larger trials were needed, with sufficiently intense exercise interventions. The second empirical study was a large (n=906), pragmatic randomised controlled trial (Fit2Quit), of the effectiveness and cost-effectiveness on smoking abstinence rates at six months of a telephone counselling exercise intervention when added to usual smoking cessation support delivered by the New Zealand Quitline, compared with usual smoking cessation support alone. No statistically significant differences were found between groups for smoking abstinence. However, a treatment effect for leisure time physical activity in favour of the intervention group (difference = 219.11 minutes per week; 95% CI 52.65, 385.58) was detected. The number of intervention calls delivered significantly decreased the probability of smoking (OR 0.89, 95% CI 0.81, 0.97, p-value 0.011) in the intervention group. Overall, the intervention was not cost-effective in the short-term, but was cost-effective for those that adhered to the intervention. There were no differences between groups for any of the psychological or anthropometric outcomes measured in the face-to-face sub-study. A subsample (n=219) of Fit2Quit participants completed additional face-to-face measures. Qualitative exit interviews (n=20) were also conducted with intervention group participants to explore their perspectives on the acceptability of the intervention. The intervention was well-received by most participants interviewed in the qualitative subsample, with the provision of support and encouragement from the participant support person considered the most beneficial aspect. Modifying future interventions to include greater tailoring of the call schedule, greater face-to-face contact, and an exercise support group may enhance effectiveness. Conclusions: A short bout of vigorous intensity exercise reduces cigarette cravings during temporary smoking abstinence. This effect may be explained by autonomic nervous system responses and post-exercise increases in noradrenaline. However, further research with a larger sample is required to determine this. A six-month telephone-delivered exercise intervention combined with usual cessation support does not improve quit rates compared with usual cessation care alone, but appears to be an acceptable intervention approach. Findings suggest that the effectiveness of this approach may be enhanced if only those motivated to change their exercise behaviour are recruited and poor adherence rates can be addressed Recommendations for future research include exploring changes in heart rate variability, noradrenaline, and cortisol after vigorous exercise, increasing translation of the acute-effects of exercise observed in the laboratory to the real-world setting, and increasing adherence to existing intervention strategies. Exercise does appear to have a role to play as a smoking cessation aid, but only for those willing, motivated and ready to make a change to their exercise behaviour. Thus, offering exercise to motivated individuals as one of a range of treatment options for smoking cessation could be a helpful approach. |
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