Is there a relationship between smoking and asthma in adults?

Effects of body mass index, tobacco smoking, alcohol drinking and solid fuel use on the risk of asthma: Individual Participant Data (IPD) meta-analysis of 175 000 individuals from 51 nationally representative surveys

Background

We assessed the relationship of body mass index (BMI), smoking, drinking and solid fuel use (r; SFU), and the individual and combined effects of these factors on wheezing symptoms (WS) and on diagnosed asthma (DA).

Methods

We analysed 175 000 individuals from 51 nationally representative surveys, using self-reports of WS and DA as the measures of asthma. The fixed-effects and random-effects estimates of the pooled ORs between asthma and underweight (BMI <18.5 kg/m²), obesity (BMI ≥30 kg/m²), smoking, drinking and SFU were reported.

Results

The pooled risks of all individual risk factors were significantly associated with WS and DA (with the exception of current smoking with DA in women and SFU with DA in both genders). Stronger dose–response relationships were seen in women for smoking amounts and duration; BMI showed stronger quadratic relationships. The combined risks were generally larger in women than in men, with significant risks for underweight (OR=2.73) as well as obese (OR=2.00) smokers for WS (OR=2.13 and OR=1.58 for DA, respectively). The magnitude of the combined effects from low/high BMI, smoking and drinking were also consistently higher among women than among men in WS and DA. SFU among underweight smokers also had positive association with WS (men and women) and DA (women).

Conclusions

BMI, smoking, drinking and SFU—in combination—are associated with double or triple the risk of development of asthma. These risk factors might help explain the wide variation in asthma burden across countries.

Effect of indoor air pollution from biomass and solid fuel combustion on prevalence of self-reported asthma among adult men and women in India: findings from a nationwide large-scale cross-sectional survey

OBJECTIVES

Increasing prevalence of asthma in developing countries has been a significant challenge for public health in recent decades. A number of studies have suggested that ambient air pollution can trigger asthma attacks. Biomass and solid fuels are a major source of indoor air pollution, but in developing countries the health effects of indoor air pollution are poorly understood. In this study we examined the effect of cooking smoke produced by biomass and solid fuel combustion on the reported prevalence of asthma among adult men and women in India.

METHODS

The analysis is based on 99,574 women and 56,742 men aged between 20 and 49 years included in India's third National Family Health Survey conducted in 2005-2006. Effects of exposure to cooking smoke, determined by the type of fuel used for cooking such as biomass and solid fuels versus cleaner fuels, on the reported prevalence of asthma were estimated using multivariate logistic regression. Since the effects of cooking smoke are likely to be confounded with effects of tobacco smoking, age, and other such factors, the analysis was carried out after statistically controlling for such factors.

RESULTS

The results indicate that adult women living in households using biomass and solid fuels have a significantly higher risk of asthma than those living in households using cleaner fuels (OR: 1.26; 95%CI: 1.06-1.49; p = .010), even after controlling for the effects of a number of potentially confounding factors. Interestingly, this effect was not found among men (OR: 0.98; 95%CI: 0.77-1.24; p = .846). However, tobacco smoking was associated with higher asthma prevalence among both women (OR: 1.72; 95%CI: 1.34-2.21; p < .0001) and men (OR: 1.35; 95%CI: 1.49-2.25; p < .0001). Combined effects of biomass and solid fuel use and tobacco smoke on the risk of asthma were greater and more significant in women (OR: 2.16; 95%CI: 1.58-2.94; p < .0001) than they were in men (OR: 1.34; 95%CI: 1.04-1.72; p = .024).

CONCLUSIONS

The findings have important program and policy implications for countries such as India, where large proportions of the population still rely on polluting biomass fuels for cooking and heating. Decreasing household biomass and solid fuel use and increasing use of improved stove technology may decrease the health effects of indoor air pollution. More epidemiological research with better measures of smoke exposure and clinical measures of asthma is needed to validate the findings.

Smoking and asthma in men and women with normal weight, overweight, and obesity

BACKGROUND

There is a complex interrelationship among smoking, body weight, and asthma. It needs to be clarified whether smoking is related to an increased risk of asthma after taking into account for relative body weight.

OBJECTIVE

To examine the association between cigarette smoking and the prevalence of asthma in Canadian men and women with normal weight, overweight, and obesity.

METHODS

The analysis was based on data from 112,830 Canadians aged 18 years or more who participated in a national survey in 2007-2008. A questionnaire covered the information on prevalent asthma, smoking status, height, weight, and other factors. Logistic regression analysis was used to determine the association between smoking and the prevalence of asthma stratified by sex and body mass index (BMI).

RESULTS

The crude prevalence of asthma was 6.6% for men and 9.3% for women. After adjustment for covariates, the odds ratios (ORs) for current smoking associated with asthma was 1.20 [95% confidence interval (CI): 1.01-1.43] for men with normal weight, 0.98 (95% CI: 0.81, 1.18) for overweight men, and 1.02 (95% CI: 0.80-1.30) for obese men. For women, the corresponding adjusted ORs were 1.41 (95% CI: 1.23-1.62), 1.27 (95% CI: 1.05-1.54), and 1.28 (95% CI: 1.03-1.59), respectively.

CONCLUSION

Current smoking was significantly associated with prevalent asthma in all women regardless of their relative body weight. In men, however, the association was only observed in those with under- or normal weight.

Asthma and cigarette smoking: a review of the empirical literature

The purpose of this review paper is to present and evaluate the empirical literature on the association between asthma and cigarette smoking. The authors conducted a literature search utilizing electronic search engines (i.e., PsycINFO and MEDLINE) to examine databases using the following key word algorithms: smoking OR nicotine OR tobacco AND asthma. Only articles that focused on active tobacco smoking and analyzed groups with asthma patients only were examined in the present review. Overall, empirical evidence suggests that (1) smoking is more prevalent among individuals with asthma than those without; (2) smoking is a risk candidate for the development of asthma; (3) smoking is associated with decreased asthma control and increased risk of mortality and asthma attacks and exacerbations; (4) smokers with and without asthma may have different risk factors for smoking onset as well as different smoking motives and outcome expectancies; and (5) smoking cessation is associated with improvements in lung functioning and asthma symptoms. Future work in this domain of study will lead to clinically relevant health care advances as well as the development of theoretically driven, methodologically diverse lines of research exploring asthma-smoking comorbidity issues.

Smoking affects response to inhaled corticosteroids or leukotriene receptor antagonists in asthma

RATIONALE

One-quarter to one-third of individuals with asthma smoke, which may affect response to therapy and contribute to poor asthma control.

OBJECTIVES

To determine if the response to an inhaled corticosteroid or a leukotriene receptor antagonist is attenuated in individuals with asthma who smoke.

METHODS

In a multicenter, placebo-controlled, double-blind, double-dummy, crossover trial, 44 nonsmokers and 39 light smokers with mild asthma were assigned randomly to treatment twice daily with inhaled beclomethasone and once daily with oral montelukast.

MEASUREMENTS AND MAIN RESULTS

Primary outcome was change in prebronchodilator FEV(1) in smokers versus nonsmokers. Secondary outcomes included peak flow, PC(20) methacholine, symptoms, quality of life, and markers of airway inflammation. Despite similar FEV(1), bronchodilator response, and sensitivity to methacholine at baseline, subjects with asthma who smoked had significantly more symptoms, worse quality of life, and lower daily peak flow than nonsmokers. Adherence to therapy did not differ significantly between smokers and nonsmokers, or between treatment arms. Beclomethasone significantly reduced sputum eosinophils and eosinophil cationic protein (ECP) in both smokers and nonsmokers, but increased FEV(1) (170 ml, p = 0.0003) only in nonsmokers. Montelukast significantly increased a.m. peak flow in smokers (12.6 L/min, p = 0.002), but not in nonsmokers.

CONCLUSIONS

In subjects with mild asthma who smoke, the response to inhaled corticosteroids is attenuated, suggesting that adjustments to standard therapy may be required to attain asthma control. The greater improvement seen in some outcomes in smokers treated with montelukast suggests that leukotrienes may be important in this setting. Larger prospective studies are required to determine whether leukotriene modifiers can be recommended for managing asthma in patients who smoke.

An overview of the association between allergy and cancer

Numerous epidemiological studies have evaluated some aspect of the association between a history of allergy and cancer occurrence. In this article, an overview of the epidemiological evidence is presented with a discussion of a number of methodological issues important in this area of study. Literature searches were conducted using the MEDLINE database from 1966 through to August 2005 to identify articles that explored a personal history of allergic disorders as a risk factor for cancer. Although it is difficult to draw conclusions between allergy and cancer at many sites because of insufficient evidence or a lack of consistency both within and among studies completed to date, strong inverse associations have been reported for pancreatic cancer and glioma, whereas lung cancer was positively associated with asthma. Additional studies are needed to confirm these finding and to address the limitations of previous studies, including the validity and reliability of exposure measures and control for confounding. Further, large prospective studies using cancer incidence would be particularly useful, including studies using biological markers of allergic status to reduce potential misclassification and to confirm the results of previous studies based on self-report. There is also a need for further basic research to clarify a potential mechanism, should an association exist.

Smoking, respiratory symptoms and likely asthma in young people: evidence from postal questionnaire surveys in the Wythenshawe Community Asthma Project (WYCAP)

BACKGROUND

Although it is recognised that smoking is a major risk factor for subjects with chronic obstructive pulmonary disease and is associated with respiratory symptoms, there is less agreement concerning the relationship between asthma and smoking. This study aims to examine the relationship between cigarette smoking and asthma prevalence.

METHOD

Data were used from two postal questionnaire surveys (1999 and 2001) in two general practice populations, using a respiratory questionnaire based on the ECRHQ and a generic quality of life questionnaire (EQ-5D). Only subjects less than 45 years old were included in the survey. An empirical definition of likely asthma was used based on respiratory questionnaire responses. Smoking was examined according to three categories, current smoker, ex smoker and never smoker.

RESULTS

Almost 3500 subjects were included in the analyses. Current smokers had a higher prevalence of likely asthma compared to never smokers, odds ratio (OR) 1.59 (95% confidence interval (CI) 1.24 to 2.04). and also compared to ex smokers OR 1.79 (CI 1.25 to 2.56), but there was no difference between ex smokers and never smokers (OR 1.00 (0.75-1.35)). Current smoking was also positively associated with all symptoms but not with a history of hayfever/eczema.

CONCLUSION

Although the positive association found between current smoking and obstructive airways disease is likely to be due to the effect of cigarettes on asthma, it could reflect an association with early COPD (GOLD stages 0 or 1). Smoking cessation has a beneficial effect on the prevalence of respiratory symptoms and is therefore of paramount importance among these young adults.