The acute effects of exercise on cigarette cravings, withdrawal symptoms, affect, and smoking behaviour: systematic review update and meta-analysis

RATIONALE: Smoking cessation is associated with cigarette cravings and tobacco withdrawal symptoms (TWS), and exercise appears to ameliorate many of these negative effects. A number of studies have examined the relationships between exercise, cigarette cravings, and TWS. OBJECTIVES: The objectives of this study were (a) to review and update the literature examining the effects of short bouts of exercise on cigarette cravings, TWS, affect, and smoking behaviour and (b) to conduct meta-analyses of the effect of exercise on cigarette cravings. METHODS: A systematic review of all studies published between January 2006 and June 2011 was conducted. RESULTS: Fifteen new studies were identified, 12 of which found a positive effect of exercise on cigarette cravings. The magnitude of statistically significant effect sizes for 'desire to smoke' and 'strength of desire to smoke' ranged from 0.4 to 1.98 in favour of exercise compared to passive control conditions, and peaked either during or soon after treatment. Effects were found up to 30 min post-exercise. Cigarette cravings were reduced following exercise with a wide range of intensities from isometric exercise and yoga to activity as high as 80-85 % heart rate reserve. Meta-analyses revealed weighted mean differences of -1.90 and -2.41 in 'desire to smoke' and 'strength of desire to smoke' outcomes, respectively. Measures of TWS and negative affect were reduced following light-moderate intensity exercise, but increased during vigorous exercise. CONCLUSIONS: Exercise can have a positive effect on cigarette cravings and TWS. However, the most effective exercise intensity to reduce cravings and the underlying mechanisms associated with this effect remain unclear.

Self-efficacy and social support as predictors of smoking after a quit attempt

Examined findings (e.g., A. J. Yates and J. Thain [see PA, Vol 73:28269]) that suggest that perceived social support for attempts to quit smoking is a determinant of self-efficacy (SE). 102 adults (aged 18–71 yrs) who participated in a trial of 4 smoking interventions were studied over a 10-mo follow-up period. The study attested to the validity of SE as a predictor of sustained success from an attempt to stop smoking. The tendency for SE theory to be more strongly supported in the longer term was highly consistent with the proposed mechanism for SE effects. The absence of a relationship with perceived social support might be an advantage for SE, since support was a poor predictor of outcomes during follow-up. Results suggest that perceived social influences had less utility than personal skills and SE in predicting sustained non-smoking outcomes.

Aberrations and pupil location under corneal topography and Hartmann-Shack illumination conditions

PURPOSE. This study was conducted to determine the magnitude of pupil center shift between the illumination conditions provided by corneal topography measurement (photopic illuminance) and by Hartmann-Shack aberrometry (mesopic illuminance) and to investigate the importance of this shift when calculating corneal aberrations and for the success of wavefront-guided surgical procedures. METHODS. Sixty-two subjects with emmetropia underwent corneal topography and Hartmann-Shack aberrometry. Corneal limbus and pupil edges were detected, and the differences between their respective centers were determined for both procedures. Corneal aberrations were calculated using the pupil centers for corneal topography and for Hartmann-Shack aberrometry. Bland-Altmann plots and paired t-tests were used to analyze the differences between corneal aberrations referenced to the two pupil centers. RESULTS. The mean magnitude (modulus) of the displacement of the pupil with the change of the illumination conditions was 0.21 ± 0.11 mm. The effect of this pupillary shift was manifest for coma corneal aberrations for 5-mm pupils, but the two sets of aberrations calculated with the two pupil positions were not significantly different. Sixty-eight percent of the population had differences in coma smaller than 0.05 µm, and only 4% had differences larger than 0.1 µm. Pupil displacement was not large enough to significantly affect other higher-order Zernike modes. CONCLUSIONS. Estimated corneal aberrations changed slightly between photopic and mesopic illumination conditions given by corneal topography and Hartmann-Shack aberrometry. However, this systematic pupil shift, according to the published tolerances ranges, is enough to deteriorate the optical quality below the theoretically predicted diffraction limit of wavefront-guided corneal surgery.

Corneal topography with Scheimpflug imaging and videokeratography : comparative study of normal eyes

PURPOSE: To compare the repeatability within anterior corneal topography measurements and agreement between measurements with the Pentacam HR rotating Scheimpflug camera and with a previously validated Placido disk–based videokeratoscope (Medmont E300). ------ SETTING: Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia. ----- METHODS: Normal eyes in 101 young adult subjects had corneal topography measured using the Scheimpflug camera (6 repeated measurements) and videokeratoscope (4 repeated measurements). The best-fitting axial power corneal spherocylinder was calculated and converted into power vectors. Corneal higher-order aberrations (HOAs) (up to the 8th Zernike order) were calculated using the corneal elevation data from each instrument. ----- RESULTS: Both instruments showed excellent repeatability for axial power spherocylinder measurements (repeatability coefficients <0.25 diopter; intraclass correlation coefficients >0.9) and good agreement for all power vectors. Agreement between the 2 instruments was closest when the mean of multiple measurements was used in analysis. For corneal HOAs, both instruments showed reasonable repeatability for most aberration terms and good correlation and agreement for many aberrations (eg, spherical aberration, coma, higher-order root mean square). For other aberrations (eg, trefoil and tetrafoil), the 2 instruments showed relatively poor agreement. ----- CONCLUSIONS: For normal corneas, the Scheimpflug system showed excellent repeatability and reasonable agreement with a previously validated videokeratoscope for the anterior corneal axial curvature best-fitting spherocylinder and several corneal HOAs. However, for certain aberrations with higher azimuthal frequencies, the Scheimpflug system had poor agreement with the videokeratoscope; thus, caution should be used when interpreting these corneal aberrations with the Scheimpflug system.

Sustained convergence, axial length, and corneal topography

Purpose: To investigate the influence of convergence on axial length and corneal topography in young adult subjects.---------- Methods: Fifteen emmetropic young adult subjects with normal binocular vision had axial length and corneal topography measured immediately before and after a 15-min period of base out (BO) prismatic spectacle lens wear. Two different magnitude prismatic spectacles were worn in turn (8 [DELTA] BO and 16 [DELTA] BO), and for both tasks, distance fixation was maintained for the duration of lens wear. Eight subjects returned on a separate day for further testing and had axial length measured before, during, and immediately after a 15-min convergence task.---------- Results: No significant change was found to occur in axial length either during or after the sustained convergence tasks (p > 0.6). Some small but significant changes in corneal topography were found to occur after sustained convergence. The most significant corneal change was observed after the 16 [DELTA] BO prism wear. The corneal refractive power spherocylinder power vector J0 was found to change by a small (mean change of 0.03 D after the 16 [DELTA] BO task) but statistically significant (p = 0.03) amount as a result of the convergence task (indicative of a reduction in with-the-rule corneal astigmatism after convergence). Corneal axial power was found to exhibit a significant flattening in superior regions. Conclusions: Axial length appears largely unchanged by a period of sustained convergence. However, small but significant changes occur in the topography of the cornea after convergence.