Jerome F. Walker

Behaviours of pulmonary sensory receptors during development of acute lung injury in the rabbit

We tested the hypothesis that oleic acid‐induced acute lung injury activates pulmonary nociceptors, that is, C fibre receptors (CFRs) and high‐threshold Aδ fibre receptors (HTARs). Single‐unit activity was recorded in the cervical vagus nerve and assessed before and after injecting oleic acid (75 μl kg−1i.v.) into anaesthetized, open‐chest, mechanically ventilated rabbits. Unit activities increased within seconds and peaked within a few minutes (from 0.3 ± 0.1 to 1.4 ± 0.9 impulses s−1 for CFRs and from 0.5 ± 0.1 to 1.7 ± 0.3 impulses s−1 for HTARs, both n= 8 and P < 0.05). These activities were sustained while pulmonary oedema developed and dynamic lung compliance decreased over the 90 min observation period. Activities in slowly adapting receptors and rapidly adapting receptors were also increased; however, their responsiveness to airway pressure stimulation decreased progressively. We conclude that pulmonary nociceptors are stimulated during acute lung injury. The dual nociceptor system, consisting of both non‐myelinated CFRs and myelinated HTARs, may play an important role in the pathophysiological process of acute lung injury‐induced respiratory responses.

Association Between Physical Activity and Inflammatory Markers Among U.S. Adults With Chronic Obstructive Pulmonary Disease

Purpose. Chronic obstructive pulmonary disease (COPD) may cause not only inflammation in the lungs but also systemic effects. One potential strategy to reduce systemic inflammation and attenuate disease progression is physical activity (PA). However, no nationally representative studies, to our knowledge, have examined the association between objectively measured physical activity and inflammation among those with COPD. Design. Cross-sectional. Setting. National Health and Nutrition Examination Survey 2003–2006. Subjects. Two hundred thirty-eight former or current smokers with self-reported COPD who had complete data on study variables. Measures. Participants wore an accelerometer for ≥4 days to assess light-intensity PA (LPA), moderate-to-vigorous PA (MVPA), and total physical activity (TPA); completed questionnaires to assess self-reported COPD and smoking status; and had their blood taken to assess white blood cell (WBC) and neutrophil levels. Analysis. Multivariable linear regression analysis was used. Results. LPA (β = –.0004), MVPA (β = –.04), and TPA (β = –.0004) were significantly inversely associated with WBC level. Similarly, LPA (β = –.001) and TPA (β = –.001) were significantly inversely associated with neutrophils; however, MVPA was marginally associated with neutrophils (β = –.05; p =.06). Conclusion. These analyses demonstrate an inverse association between objectively measured PA and inflammation among current or former smokers with COPD. If these findings are confirmed elsewhere, then PA among those with COPD may serve as an anti-inflammatory strategy to possibly decrease cardiovascular and metabolic disease occurrence.

Development of a Conceptual Model for Smoking Cessation: Physical Activity, Neurocognition, and Executive Functioning

Purpose: Considerable research has shown adverse neurobiological effects of chronic alcohol use, including long-term and potentially permanent changes in the structure and function of the brain; however, much less is known about the neurobiological consequences of chronic smoking, as it has largely been ignored until recently. In this article, we present a conceptual model proposing the effects of smoking on neurocognition and the role that physical activity may play in this relationship as well as its role in smoking cessation. Methods: Pertinent published peer-reviewed articles deposited in PubMed delineating the pathways in the proposed model were reviewed. Results: The proposed model, which is supported by emerging research, demonstrates a bidirectional relationship between smoking and executive functioning. In support of our conceptual model, physical activity may moderate this relationship and indirectly influence smoking behavior through physical activity-induced changes in executive functioning. Conclusions: Our model may have implications for aiding smoking cessation efforts through the promotion of physical activity as a mechanism for preventing smoking-induced deficits in neurocognition and executive function.

Longitudinal Examination of Predictors of Smoking Cessation in a National Sample of U.S. Adolescent and Young Adult Smokers

INTRODUCTION To better inform the development of smoking cessation programs for adolescents and young adults, a prospective study was employed to systematically examine behavioral, demographic, health, and psychosocial determinants of smoking cessation. METHODS Data from the 2003-2005 National Youth Smoking Cessation Survey were used. Of 2,582 smokers aged 16-24 years sampled, 1,354 provided complete baseline telephone interview data on the study variables, and their self-reported smoking status at 2-year follow-up was known (currently smoking vs. not smoking). Multivariable logistic regression analysis was employed to examine independent predictors of smoking status (outcome variable) at the 2-year follow-up period. RESULTS Four of 5 participants remained smokers after 2 years. Of the high nicotine dependence smokers, 90% remained smokers at follow-up; of the low nicotine dependence smokers, 77% remained smokers at follow-up. Higher nicotine dependence smokers started smoking earlier in life (13.2 vs. 14.3 years; p < .05). Similarly, those not smoking at the 2-year follow-up period started smoking later in life than those still smoking (14.5 vs. 13.7 years). Along with nicotine dependence, various psychosocial and demographic variables at baseline predicted smoking status at the 2-year follow-up period. CONCLUSIONS Identifiable demographic and psychosocial factors influence smoking behavior among U.S. adolescents and young adults. Even low nicotine dependence is a strong predictor of follow-up smoking behavior. This, coupled with the early smoking age of high nicotine dependence smokers, underscores the importance of early nicotine avoidance among youth.

Combined association of physical activity and diet with C-reactive protein among smokers

BackgroundIn the general population, both physical activity and dietary behavior are independently associated with less systemic inflammation, with this relationship less examined among smokers. To our knowledge, no study has examined the combined association of both physical activity and dietary behavior on systemic inflammation among daily smokers, which was the purpose of this study.MethodsData from the 2003–2006 NHANES were employed. 810 adult smokers provided C-reactive protein data (CRP; a marker of inflammation), and sufficient physical activity (accelerometry) and dietary data (healthy eating index).ResultsThe fully adjusted model showed that participants meeting physical activity guidelines and eating a healthy diet (β = −0.34, p = 0.03) had lower CRP levels when compared to those not engaging in these health behaviors, but only having one health behavior was not a significant predictor of CRP (β = −0.19, p = 0.14).ConclusionsSmokers engaging in regular physical activity while consuming a healthy diet demonstrate lower CRP levels than their counterparts. When taken together, these behaviors may mitigate inflammation associated with various chronic diseases, which is of particular importance as very few smokers successfully quit smoking.

Physical Activity Moderates the Association Between Nicotine Dependence and Depression Among U.S. Smokers

Purpose. Research demonstrates that nicotine dependence and depression are associated and that physical activity is effective in reducing depression symptoms. However, our understanding of the potential beneficial effects of physical activity on depression in current smokers is more limited. The purpose of this study was to examine whether physical activity moderates the association between nicotine dependence and depression in U.S. smokers. Design. Cross-sectional. Setting. National Health and Nutrition Examination Survey 2005–2006. Subjects. Four hundred forty-one current adult smokers. Measures. Participants wore an accelerometer for at least 4 days and completed questionnaires to assess nicotine dependence and depression. Analysis. Effect modification and statistical interaction models were used. Results. Both models were significant. With regard to the statistical interaction model, and after controlling for age, gender, race/ethnicity, education, comorbidity index, homocysteine, cotinine, total cholesterol, sedentary behavior, and vitamins C, D, and E, objectively measured physical activity moderated the association between nicotine dependence and depression (interaction variable: odds ratio = 3.43; 95% confidence interval: 1.02–11.51; p = .04). Conclusion. In this national sample of current smokers, physical activity moderated the association between nicotine dependence and depression. These results suggest that those individuals with nicotine dependence and who are less physically active are more likely to be depressed than what would be expected on the basis of the individual effects of nicotine and physical inactivity separately.

Association between physical activity and major depressive disorder among current or former smokers with pulmonary disease

OBJECTIVE To examine the association between physical activity and major depressive disorder (MDD) in a nationally representative sample of current or former smokers with pulmonary impairments. METHODS The analyzed sample from the National Health and Nutrition Examination Survey (NHANES) 2007-2010 included 536 adults who indicated that they were current or former smokers, had at least mild pulmonary impairment (FEV1/FVC<0.70), and provided depression and physical activity data. RESULTS After controlling for asthma status, pulmonary impairment, age, poverty-to-income ratio (PIR), education, gender, marital status, body mass index (BMI), cotinine, comorbidity index, race-ethnicity, and smoking status, those who met physical activity guidelines had a 59% (odds ratio (OR)=0.41; 95% confidence interval (CI): 0.18-0.94) lower odds of having MDD. Using multivariate linear regression with depression symptoms as the outcome variable, and after adjustments, physical activity was inversely associated with depression symptoms in a dose-response manner; lowest tertile was the referent group, middle tertile coefficient: -1.06 (95% CI: -1.98 to -0.14), and highest tertile coefficient: -1.10 (95% CI: -1.84 to -0.34). CONCLUSIONS Physical activity inversely associates with MDD in adults with pulmonary impairments, and does so in a dose-response manner. This suggests that individuals with pulmonary impairments should be encouraged to engage in enjoyable, safe forms of physical activity in a progressive manner.

Exercise Facilitates Smoking Cessation Indirectly via Improvements In Smoking-Specific Self-Efficacy: Prospective Cohort Study Among a National Sample of Young Smokers

OBJECTIVE The purpose of this study was to examine whether exercise is associated with 2-year follow-up smoking status through its influence on smoking-specific self-efficacy. METHODS Longitudinal data from the 2003-2005 National Youth Smoking Cessation Survey were used, including 1,228 participants (16-24 years). A questionnaire was used to examine baseline exercise levels, baseline smoking-specific self-efficacy, follow-up smoking status, and the covariates. RESULTS Baseline exercise was associated with baseline self-efficacy (β=0.04, p<0.001) after adjusting for age category, sex, race-ethnicity, education, and nicotine dependence. Baseline self-efficacy, in turn, was associated with 2-year smoking status (β=0.23, p<0.001) after adjustments. There was no adjusted direct effect of baseline exercise on 2-year smoking status (β=0.001, p=0.95); however, the adjusted indirect effect of baseline self-efficacy on the relationship between exercise and 2-year smoking status was significant (β=0.008, bootstrapped lower and upper CI: 0.002-0.02; p<0.05). The mediation ratio was 0.837, which indicates that smoking-specific self-efficacy mediates 84% of the total effect of exercise on smoking status. CONCLUSIONS Among daily smokers, exercise may help to facilitate smoking cessation via exercise-induced increases in smoking-specific self-efficacy.

Association of Longitudinal Changes of Physical Activity on Smoking Cessation Among Young Daily Smokers

OBJECTIVE To our knowledge, no longitudinal epidemiological study among daily smokers has examined the effects of physical activity change/ trajectory on smoking cessation. The purpose of this study was to examine the longitudinal effects of changes in physical activity on smoking cessation among a national sample of young (16-24 y) daily smokers. METHODS Data from the 2003-2005 National Youth Smoking Cessation Survey were used (N = 1178). Using hierarchical agglomerative cluster analysis, 5 distinct self-reported physical activity trajectories over 3 time periods (baseline, 12-month, and 24-month follow-up) were observed, including stable low physical activity, decreasing physical activity, curvilinear physical activity, stable high physical activity, and increasing physical activity. Nicotine dependence (Heaviness of Smoking Index) and demographic parameters were assessed via survey. RESULTS With stable low physical activity (16.2% quit smoking) serving as the referent group, those in the stable high physical activity (24.8% quit smoking) group had 1.8 greater odds of not smoking at the 24-month follow-up period (odds ratio = 1.81; 95% confidence interval, 1.12-2.91) after adjusting for nicotine dependence, age, gender, race-ethnicity, and education. CONCLUSIONS Maintenance of regular physical activity among young daily smokers may help to facilitate smoking cessation.

Muscle strengthening activity associates with reduced all-cause mortality in COPD:

Objective Emerging research suggests that aerobic-based physical activity may help to promote survival among chronic obstructive pulmonary disease patients. However, the extent to which engagement in resistance training on survival among chronic obstructive pulmonary disease patients is relatively unknown. Therefore, the purpose of this study was to examine the independent associations of muscle strengthening activities on all-cause mortality among a national sample of U.S. adults with chronic obstructive pulmonary disease. We hypothesize that muscle strengthening activities will be inversely associated with all-cause mortality. Methods Data from the 2003–2006 NHANES were employed, with follow-up through 2011. Aerobic-based physical activity was objectively measured via accelerometry, muscle strengthening activities engagement was assessed via self-report, and chronic obstructive pulmonary disease was assessed via physician-diagnosis. Results Analysis included 385 adults (20 + yrs) with chronic obstructive pulmonary disease, who represent 13.3 million chronic obstructive pulmonary disease patients in the USA. The median follow-up period was 78 months (IQR=64–90), with 82 chronic obstructive pulmonary disease patients dying during this period. For a two muscle strengthening activity sessions/week increase (consistent with national guidelines), chronic obstructive pulmonary disease patients had a 29% reduced risk of all-cause mortality (HR=0.71; 95% CI: 0.51–0.99; P = 0.04). Conclusion Participation in muscle strengthening activities, independent of aerobic-based physical activity and other potential confounders, is associated with greater survival among chronic obstructive pulmonary disease patients.