PREVALENCE OF CHRONIC BRONCHITIS IN AN AMERICAN MALE URBAN INDUSTRIAL POPULATION

Systematic review with meta-analysis of the epidemiological evidence relating smoking to COPD, chronic bronchitis and emphysema

BACKGROUND

Smoking is a known cause of the outcomes COPD, chronic bronchitis (CB) and emphysema, but no previous systematic review exists. We summarize evidence for various smoking indices.

METHODS

Based on MEDLINE searches and other sources we obtained papers published to 2006 describing epidemiological studies relating incidence or prevalence of these outcomes to smoking. Studies in children or adolescents, or in populations at high respiratory disease risk or with co-existing diseases were excluded. Study-specific data were extracted on design, exposures and outcomes considered, and confounder adjustment. For each outcome RRs/ORs and 95% CIs were extracted for ever, current and ex smoking and various dose response indices, and meta-analyses and meta-regressions conducted to determine how relationships were modified by various study and RR characteristics.

RESULTS

Of 218 studies identified, 133 provide data for COPD, 101 for CB and 28 for emphysema. RR estimates are markedly heterogeneous. Based on random-effects meta-analyses of most-adjusted RR/ORs, estimates are elevated for ever smoking (COPD 2.89, CI 2.63-3.17, n = 129 RRs; CB 2.69, 2.50-2.90, n = 114; emphysema 4.51, 3.38-6.02, n = 28), current smoking (COPD 3.51, 3.08-3.99; CB 3.41, 3.13-3.72; emphysema 4.87, 2.83-8.41) and ex smoking (COPD 2.35, 2.11-2.63; CB 1.63, 1.50-1.78; emphysema 3.52, 2.51-4.94). For COPD, RRs are higher for males, for studies conducted in North America, for cigarette smoking rather than any product smoking, and where the unexposed base is never smoking any product, and are markedly lower when asthma is included in the COPD definition. Variations by sex, continent, smoking product and unexposed group are in the same direction for CB, but less clearly demonstrated. For all outcomes RRs are higher when based on mortality, and for COPD are markedly lower when based on lung function. For all outcomes, risk increases with amount smoked and pack-years. Limited data show risk decreases with increasing starting age for COPD and CB and with increasing quitting duration for COPD. No clear relationship is seen with duration of smoking.

CONCLUSIONS

The results confirm and quantify the causal relationships with smoking.

Domestic biomass fuel combustion and chronic bronchitis in two rural Bolivian villages

BACKGROUND

Chronic bronchitis is an important public health problem worldwide. A study was undertaken to examine the association between exposure to air pollution from domestic biomass fuel combustion and chronic bronchitis in two rural Bolivian highland villages: a village in which cooking is done exclusively indoors and a village in which cooking is done primarily outdoors. Apart from this difference, the villages were virtually identical in terms of socioeconomic status, climate, altitude, access to health care, and other potential confounders.

METHODS

Pollution exposure was assessed by combining information on concentrations of particulate matter of <10 microm diameter (PM(10)) in 12 randomly selected households in each village in all potential microenvironments of exposure with time allocation information. The prevalence of chronic bronchitis was assessed using the British Medical Research Council's questionnaire on individuals >20 years of age in both villages (n = 241).

RESULTS

Daily pollution exposure was significantly higher in the indoor cooking village (range for adults: 9840-15 120 microg-h/m(3)) than in the outdoor cooking village (range for adults: 5520-6240 microg-h/m(3)) for both seasons and for men and women. The overall prevalence of chronic bronchitis was 22% and 13% for the indoor and outdoor cooking villages, respectively. Logistic regression analysis, which excluded the few smokers present in the population, showed a 60% reduced risk of chronic bronchitis in the outdoor cooking village compared with the indoor cooking village (OR 0.4; 95% CI 0.2 to 0.8; p = 0.0102) after adjusting for age and sex. Individuals aged >40 years were 4.3 times more likely to have chronic bronchitis than the younger age group (OR = 4.3; 95% CI 2.0 to 9.3; p = 0.0002). There was no significant difference in the prevalence of chronic bronchitis in men and women.

CONCLUSIONS

The results of this study suggest an association between chronic bronchitis and exposure to domestic biomass fuel combustion, but further large scale studies from other areas of the developing world are needed to confirm the association. Results from this and other studies will assist the development of culturally acceptable and feasible alternatives to the high exposure cooking stoves currently being used by most people worldwide.

Prevalence of chronic bronchitis in a rural community of the Hill Region of Nepal

A house to house survey of everyone aged 20 years and above living in a rural community in the Hill Region of Nepal, situated about 16 km outside Kathmandu city, was conducted to determine the prevalence of chronic bronchitis and cor pulmonale. Of the total eligible population, 2826 (95.5%) were interviewed. Chronic bronchitis was diagnosed according to the British Medical Research Council criteria, and emphysema and cor pulmonale according to the World Health Organisation expert committee criteria. The crude prevalence of chronic bronchitis was found to be 18.3%. The prevalence rate of chronic bronchitis was similar in men and women, whereas in most parts of the world much lower rates have been recorded in women. Study of a random sample of 85 individuals with chronic bronchitis showed that 57.4% had evidence of airways obstruction, whereas 15.8% of a representative sample (n = 111) of the surveyed population (excluding those with chronic bronchitis) showed evidence of airway obstruction. Of 516 subjects diagnosed as having chronic bronchitis, 382 were subsequently investigated in hospital, 134 having declined further investigation. The diagnosis was confirmed in most of the patients (93.2%) who were investigated. Other diseases played an insignificant part in the production of the observed high prevalence rates of chronic bronchitis. Of the 382 patients studied in hospital, 87 had emphysema and 42 had cor pulmonale, yielding overall prevalence rates for these two conditions of at least 3.1% and at least 1.5% respectively.

Prevalence of chronic bronchitis in an industrial population in North India

A survey for the prevalence of chronic bronchitis in an industrial population in North India is reported. The prevalence of chronic bronchitis is 12.5 percent in 473 subjects between the ages of 17 and 64 years. The prevalence rate of chronic bronchitis is comparable to that observed in areas of low community air pollution in Europe and North America. There is no age-related rise in the frequency of respiratory symptoms. The consumption of tobacco in these subjects is low and is comparable to tobacco consumption of light smokers. The prevalence of chronic bronchitis in smokers is five times the prevalence in non-smokers and is similar to the values reported for light smokers in other surveys. These observations suggest that cigarette smoking is associated with the development of chronic bronchitis, and the differences in the prevalence rate of chronic bronchitis between this survey and other surveys conducted in Europe and North America are mainly due to differences in smoking habits. Air pollution has a minor effect only and ethnic differences do not appear to play any part. Forced expired volume in one second shows a negative correlation with age. It is lower in asymptomatic smokers than in non-smokers and is lower in chronic bronchitis than in controls.