Decrease in ventilatory capacity between ages of 50 and 54 in representative sample of Swedish men

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.

Systematic review of the evidence relating FEV1 decline to giving up smoking

BACKGROUND

The rate of forced expiratory volume in 1 second (FEV1) decline ("beta") is a marker of chronic obstructive pulmonary disease risk. The reduction in beta after quitting smoking is an upper limit for the reduction achievable from switching to novel nicotine delivery products. We review available evidence to estimate this reduction and quantify the relationship of smoking to beta.

METHODS

Studies were identified, in healthy individuals or patients with respiratory disease, that provided data on beta over at least 2 years of follow-up, separately for those who gave up smoking and other smoking groups. Publications to June 2010 were considered. Independent beta estimates were derived for four main smoking groups: never smokers, ex-smokers (before baseline), quitters (during follow-up) and continuing smokers. Unweighted and inverse variance-weighted regression analyses compared betas in the smoking groups, and in continuing smokers by amount smoked, and estimated whether beta or beta differences between smoking groups varied by age, sex and other factors.

RESULTS

Forty-seven studies had relevant data, 28 for both sexes and 19 for males. Sixteen studies started before 1970. Mean follow-up was 11 years. On the basis of weighted analysis of 303 betas for the four smoking groups, never smokers had a beta 10.8 mL/yr (95% confidence interval (CI), 8.9 to 12.8) less than continuing smokers. Betas for ex-smokers were 12.4 mL/yr (95% CI, 10.1 to 14.7) less than for continuing smokers, and for quitters, 8.5 mL/yr (95% CI, 5.6 to 11.4) less. These betas were similar to that for never smokers. In continuing smokers, beta increased 0.33 mL/yr per cigarette/day. Beta differences between continuing smokers and those who gave up were greater in patients with respiratory disease or with reduced baseline lung function, but were not clearly related to age or sex.

CONCLUSION

The available data have numerous limitations, but clearly show that continuing smokers have a beta that is dose-related and over 10 mL/yr greater than in never smokers, ex-smokers or quitters. The greater decline in those with respiratory disease or reduced lung function is consistent with some smokers having a more rapid rate of FEV1 decline. These results help in designing studies comparing continuing smokers of conventional cigarettes and switchers to novel products.

A review of the role of FEV1 in the COPD paradigm

Historically, spirometry has been the objective measure used to confirm a symptom-based clinical suspicion of COPD. The third National Health and Nutrition Examination Survey (NHANES III) created a strong rationale for early identification and intervention in COPD by documenting the ability of spirometry to detect mild airflow problems in many asymptomatic smokers. Predicted values for spirometry, however, must be adjusted to account for variations in age, gender, height, ethnicity and race. Many experts agree that NHANES III reference equations are much better suited to COPD practice than most other predicted value standards. However, standards other than NHANES III have been adopted in current medical guidelines; standards that may inappropriately classify younger adults as normal and older adults as abnormal, potentially leading to widespread misdiagnosis and mis-directed therapies in clinical practice. Despite the shortcomings of established diagnostic predicted values, spirometry remains the best available tool for early and accurate diagnosis of COPD in those at risk for the disease, and is also useful in conjunction with other modalities in patients with established disease to determine prognosis and assessing therapeutic benefits. In the clinical trial settings, as well as in day-to-day practice, spirometry results should be combined with other endpoints in order to better reflect overall patient status. This review highlights key medical evidence surrounding both usefulness and limitations of FEV(1) in the setting of COPD.

State of the Art. A structural and functional assessment of the lung via multidetector-row computed tomography: phenotyping chronic obstructive pulmonary disease

With advances in multidetector-row computed tomography (MDCT), it is now possible to image the lung in 10 s or less and accurately extract the lungs, lobes, and airway tree to the fifth- through seventh-generation bronchi and to regionally characterize lung density, texture, ventilation, and perfusion. These methods are now being used to phenotype the lung in health and disease and to gain insights into the etiology of pathologic processes. This article outlines the application of these methodologies with specific emphasis on chronic obstructive pulmonary disease. We demonstrate the use of our methods for assessing regional ventilation and perfusion and demonstrate early data that show, in a sheep model, a regionally intact hypoxic pulmonary vasoconstrictor (HPV) response with an apparent inhibition of HPV regionally in the presence of inflammation. We present the hypothesis that, in subjects with pulmonary emphysema, one major contributing factor leading to parenchymal destruction is the lack of a regional blunting of HPV when the regional hypoxia is related to regional inflammatory events (bronchiolitis or alveolar flooding). If maintaining adequate blood flow to inflamed lung regions is critical to the nondestructive resolution of inflammatory events, the pathologic condition whereby HPV is sustained in regions of inflammation would likely have its greatest effect in the lung apices where blood flow is already reduced in the upright body posture.

Smoking and lung function of Lung Health Study participants after 11 years

Eleven years after Lung Health Study (LHS) entry, we performed spirometry in 77.4% of surviving participants who enrolled in a long-term follow-up study. Those not enrolling tended to be younger male heavy smokers who continued to smoke during the LHS. Their initial LHS lung function, after adjustment for these factors, did not differ from that of enrollees. Smoking habits by original LHS treatment groups (smoking intervention vs. usual care) tended to converge, but 93% of participants who were abstinent throughout the LHS were still abstinent at 11 years. Differences in lung function between treatment groups persisted; smoking intervention participants had less decline in FEV(1) than usual care participants. Men who quit at the beginning of the LHS had an FEV(1) rate of decline of 30.2 ml/year, whereas women who quit declined at 21.5 ml/year. Men continuing to smoke throughout the 11 years declined by 66.1 ml/year, and women continuing to smoke declined by 54.2 ml/year. When decline in FEV(1) was expressed as a percentage of predicted normal value, no significant sex-based difference was apparent among continuing smokers. At 11 years, 38% of continuing smokers had an FEV(1) less than 60% of the predicted normal value compared with 10% of sustained quitters.

Characteristics associated with rapid decline in forced expiratory volume

Cigarette smoking is known to accelerate decline of pulmonary function; however, the role of other factors is less clear. Characteristics of individuals who experienced rapid decline in forced expiratory volume in 1-sec (FEV1) were examined in 4451 Japanese-American men from the Honolulu Heart Program who were aged 45 to 68 years at baseline (1965-1968) and who produced three acceptable FEV1 measures over a 6-year period. Average annual rates of FEV1 decline were calculated by use of within-person regression and were categorized as rapid (> or = 60 ml/y), moderate (30 to 59 ml/y) or slow (< 30 ml/y). Lifestyle and biologic factors were compared by FEV1 decline categories after adjustment for age. A logistic regression model showed that continued smoking during follow-up, cigarette pack-years, wheezing, coronary heart disease, alcohol intake, and reduced subscapular skinfold were significantly associated with rapid FEV1 decline, after adjustment for age, height, cholesterol, an indicator of Japanese diet, and education. When analyses were restricted to continuous smokers, cigarette pack-years, wheezing, and reduced subscapular skinfold were found to be independent predictors. Among never smokers, lower educational attainment was a predictor of rapid FEV1 decline, and the association involving subscapular skinfold approached significance (P < 0.07). These characteristics may be useful in identifying subgroups of the population who are at increased risk of accelerated decline in pulmonary function and thus would be most likely to benefit from appropriate intervention.

The effect of intermittent negative pressure ventilation and long-term oxygen therapy for patients with COPD. A 4-year study

We evaluated retrospectively the effect of long-term oxygen therapy (LTOT) on the prognosis of 35 patients with chronic obstructive pulmonary disease (COPD) and chronic respiratory insufficiency (group A) who were admitted to our respiratory intensive care unit from 1984 to 1986 for acute respiratory failure (ARF). All subjects were given intermittent negative pressure ventilation (INPV) by means of an iron lung to overcome the acute episode and were treated with LTOT after discharge. Forty-four patients with COPD who were treated with the same ventilatory method to overcome an acute disease exacerbation and who were not given LTOT were used as controls (group B). Both groups were followed up for at least 48 months. All relapses of ARF were treated by iron lung in both groups A and B. The overall survival was significantly better in group A than in group B (p = 0.05 by F test) indicating that LTOT improves survival in patients with COPD after a bout of ARF treated with mechanical ventilation. Therefore, combining INPV with LTOT for overcoming acute episodes and relapses of ARF appears to improve the prognosis of patients with COPD.

Pulmonary function in relation to cigarette smoking and smoking cessation. MRFIT Research Group

BACKGROUND

More than half of the subjects in the MRFIT smoked at baseline and 10% of the subjects stopped smoking permanently during the first year of the trial. In this report, rates of decline in forced expiratory volume in 1 sec (FEV1) are compared for early permanent quitters and smokers who continued to smoke throughout the trial.

METHODS

Since pulmonary function testing was not standardized across all centers until the third annual visit cycle, change in FEV1 is examined over the latter half of the trial; the level of FEV1 is analyzed cross-sectionally at the midpoint of the trial. Analyses are limited to 4,926 subjects who never used beta-blockers or smoked cigars, cigarillos, or pipes during the trial and who had annual FEV1s measured over 2-4 years in the latter half of the trial.

RESULTS

Quitters during the first 12 months experienced smaller declines in FEV1 over the latter half of the trial than continuing smokers, with -50.7 ml/year versus -59.0 ml/year, respectively, adjusted for the level of FEV1 (P = 0.05). Cross-sectionally, those who had never smoked, former smokers, quitters, and continuing smokers showed a gradient of decreasing FEV1, and all four smoking groups were significantly different from each other (P less than 0.05).

CONCLUSIONS

These data suggest that if a middle-aged, healthy smoker stopped smoking permanently, he could expect his FEV1 to deteriorate at a more gradual rate 3-4 years after stopping smoking than a similar smoker who continued to smoke. No information was available for the complete MRFIT cohort on the pulmonary function effects immediately following smoking cessation.

Analysis of risk factors for stroke in a cohort of men born in 1913

We analyzed parental death from stroke and other potential risk factors in relation to the incidence of stroke among 789 men, all 54 years old at the base-line examination. During 18.5 years of follow-up, 57 men (7.2 percent) had strokes. In univariate analyses, the following characteristics correlated significantly with the incidence of stroke: increased systolic (P = 0.004) and diastolic blood pressure (P = 0.0001), larger waist circumference (P = 0.007), higher waist:hip ratio (P = 0.0004), increased plasma fibrinogen level (P = 0.01), and lower vital capacity (P = 0.03). In addition, men whose mothers had died of stroke had a threefold increase in their incidence of stroke as compared with men without such a maternal history (P = 0.0005). Potential risk factors for stroke that were not confirmed were body-mass index, serum cholesterol level, hematocrit, blood glucose level, smoking, coronary heart disease, electrocardiographic signs of left ventricular hypertrophy, and a paternal history of death from stroke. In multivariate analyses, increased blood pressure, abdominal obesity, increased plasma fibrinogen level, and maternal history still correlated significantly with the risk of stroke. A maternal history of stroke should probably be added to the list of risk factors for stroke among middle-aged men.

Cigarette smoking, aging, and decline in pulmonary function: A longitudinal study

Three serial spirometric determinations of forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1.0) were performed during a 10-yr period for 268 adult male cigarette smokers, 181 quitters, and 254 who had never smoked. Smokers were further divided into high- and low-tar consumption groups. Spirometric data were analyzed by repeated measures analyses of variance using time (aging) and smoking status as independent variables and age as a covariate. Results indicated that FVC and FEV1.0 were relatd to smoking status. For all age groups, nonsmokers performed best on spirometry, while current smokers performed worst. The decline in FEV1.0 over time was greatest in current smokers, especially the high-tar group. Loss of FVC over time was not influenced by smoking status.

Longitudinal respiratory studies in older people

Milne, J S (1978).Thorax, 33, 547-554. Longitudinal respiratory studies in older people. A random sample of older people in Edinburgh (215 men, 272 women aged 62-90 years) was examined with the MRC questionnaire on respiratory symptoms. The FEV₁ and FVC were recorded. Spirograms were repeated after one and five years and the questions after five years, the sample by then having been reduced to 133 men and 148 women.

After five years 7% of the surviving men and women had developed persistent cough and phlegm. This syndrome had disappeared in 12% of men and 2% of women. Dyspnoea had increased beyond grade 2 in 13% of men and 7% of women and had lessened only in 6% of women.

One-quarter of male and one-seventh of female cigarette smokers had given up smoking, mostly in the first year. Nearly all who stopped were symptomless before and after. In those men who stopped smoking before the study began symptom prevalence was similar to that in those who continued smoking.

Mean values of FEV₁ and FVC declined as age increased, the decline being greater in FVC with resulting rise in FEV₁%. Five-year differences in FEV₁ and FVC were symmetrically distributed with mean differences increasing with age. Mean differences in FEV₁ were 280-350 ml in men and 150-230 ml in women. Prediction equations from the first examinations remained usable for clinical work. Mean values of FEV₁ and FVC at the first examination were smaller in those who died compared with survivors, whether symptoms were present or not. The prevalence of symptoms was greater in those who died.

Smoking and intermediate alpha1-antitrypsin deficiency and lung function in middle-aged men

Lung function was evaluated in a representative population sample of 50-year-0ld men living in one Swedish city. Twenty-four smoking and 15 non-smoking men heterozygous for alpha1-antitrypsin deficiency--that is, with the protease-inhibitor (Pi1 phenotype MZ--were carefully matched for weight and smoking habit with Pi M controls. The pulmonary function of non-smoking Pi MZ subjects did not differ from that of non-smoking Pi M controls. In contrast, smoking heterozygotes showed a significant loss of elastic recoil, enlarged residual volumes, and increased closing capacity but no signs of obstructive ventilatory impairment. Most smoking Pi MZ individuals reported mild exertional dyspnoea.

Age, smoking inhalation, and pulmonary function

This study examined the relative effects of age and smoking on pulmonary function. Smoking was measured by six smoking variables, taken singly and as a composite. Subjects were 1,516 male participants in the Normative Aging Study. A stepwise multiple regression with vital capacity (VC) and forced expiratory volume at one second (FEV1.0) as the criteria accounted for 24.4% and 28.3% of the variance, respectively. Two-way analyses of variance showed that the age decline in pulmonary function was substantially greater for high inhalers than it was for low inhalers or nonsmokers. Age and the inhalation index were also noticeably and independently related to a decline in pulmonary function.

A double-blind cross-over trial of trimethoprim and sulphamethoxazole in chronic bronchitis

A double-blind cross-over trial comparing trimethoprim-sulphamethoxazole with sulphamethoxazole in patients with chronic bronchitis in their usual state of health showed that the combination was more effective in reducing the volume and purulence of the sputum. Although the patients preferred treatment with the combination, there was no objective improvement in respiratory function. There was a significant incidence of side effects.