Computation of relative risk based on simultaneous surveys: an alternative to cohort and case-control studies

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.

Using the National Health Interview Survey to understand and address the impact of tobacco in the United States: past perspectives and future considerations

OBJECTIVE

The National Health Interview Survey (NHIS) is a continuous, nationwide, household interview survey of the civilian noninstitutionalized population of the United States. This annual survey is conducted by the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. Since 1965, the survey and its supplements have provided data on issues related to the use of cigarettes and other tobacco products. This paper describes the survey, provides an overview of peer-reviewed and government-issued research that uses tobacco-related data from the NHIS, and suggests additional areas for exploration and directions for future research.

DATA SOURCES

We performed literature searches using the PubMed database, selecting articles from 1966 to 2008. Study selection. Inclusion criteria were relevancy to tobacco research and primary use of NHIS data; 117 articles met these criteria. Data extraction and synthesis. Tobacco-related data from the NHIS have been used to analyze smoking prevalence and trends; attitudes, knowledge, and beliefs; initiation; cessation and advice to quit; health care practices; health consequences; secondhand smoke exposure; and use of smokeless tobacco. To date, use of these data has had broad application; however, great potential still exists for additional use.

CONCLUSION

NHIS data provide information that can be useful to both practitioners and researchers. It is important to explore new and creative ways to best use these data and to address the full range of salient tobacco-related topics. Doing so will better inform future tobacco control research and programs.

The widening gap in death rates among income groups in the United States from 1967 to 1986

Death rates in the United States have fallen since the 1960s, but improvements have not been shared equally by all groups. This study investigates the change in inequality in mortality by income level from 1967 to 1986. Comparable death rates are constructed for 1967 and 1986 using National Mortality Followback Surveys as numerators and National Health Interview Surveys as denominators. Direct age-adjusted death rates are calculated for income levels for the U.S. noninstitutionalized civilian population 35 to 64 years old. A summary measure of inequality in mortality adjusts for differences in the size and definition of income groups in the two years. In both 1967 and 1986, mortality decreased with each rise in income level. Measured in relative terms, this inverse relationship was greater in 1986 then in 1967 for men and women, blacks and whites. Between 1967 and 1986, death rates for those with maximal income declined between two and three times more rapidly than did rates for the middle and low income groups. The greatest increase in relative inequality was seen among white males.

Impact of diabetes mellitus on mortality associated with pneumonia and influenza among non-Hispanic black and white US adults

OBJECTIVES

This study assessed the impact of diabetes on mortality associated with pneumonia and influenza among non-Hispanic Black and White US adults.

METHODS

Data were derived from the National Mortality Followback Survey (1986) and the National Health Interview Survey (1987-1989).

RESULTS

Regardless of race, sex, and socioeconomic status, people with diabetes who died at 25 to 64 years of age were more likely to have pneumonia and influenza recorded on the death certificate than people without diabetes who died at comparable ages (odds ratio [OR] = 4.0, 95% confidence interval [CI] = 2.3, 7.7). For those 65 years and older, the risk remained elevated among Whites with diabetes (OR = 2.2, 95% CI = 1.7, 2.7) but not among Blacks with diabetes (OR = 1.0, 95% CI = 0.6, 1.7). It was estimated that about 17,000 (10.3%) of the 167,000 deaths associated with pneumonia and influenza that occurred in 1986 were attributable to diabetes.

CONCLUSIONS

The impact of diabetes on deaths associated with pneumonia and influenza is substantial. Targeted immunizations among people with diabetes may reduce unnecessary deaths associated with pneumonia and influenza.

Analyzing health surveys for cancer-related objectives

Large-scale health surveys conducted by government agencies record information on a large number of health-related variables. We review the use of these data for performing analyses that address cancer-related objectives. After describing the conduct of a large-scale health survey (the third National Health and Nutrition Examination Survey [NHANES III]), we discuss some of the issues involved in analyzing data collected in such a survey. In particular, the use of sample weights in the analysis and the importance of accounting for the complex survey design when estimating standard errors are discussed. Six applications are then presented that involve the following: 1) estimating demographic factors associated with snuff use, 2) estimating the association of type of health insurance with the probability of receiving a digital rectal examination, 3) estimating the association of body iron stores with the probability of later developing cancer, 4) estimating the changing rates of mammography screening in the United States between 1987 and 1992, 5) evaluating smoking and alcohol consumption as risk factors for digestive cancer by use of a population-based, case-control study, and 6) evaluating a randomized community-intervention experiment to encourage smoking cessation. These applications use data from the National Health Interview Survey, the NHANES I Epidemiologic Followup Study, the 1986 National Mortality Followback Survey, and the Community Intervention Trial for Smoking Cessation. The availability of public-use data files is discussed for surveys sponsored by the U.S. government that collect health-related information. We demonstrate that statistical methods and computer software are available for analyzing public-use data files of surveys to address different types of cancer-related objectives.

Use of multiple surveys to estimate mortality among never, current, and former smokers: changes over a 20-year interval

OBJECTIVES

This study sought to demonstrate how data from publicly available large-scale cross-sectional health surveys can be combined to analyze changes in mortality risks among never, current, and former smokers.

METHODS

Data from the 1966/68 and 1986 National Mortality Followback Surveys and the 1970 and 1987 National Health Interview Surveys were used to estimate the distribution of never, current, and former smokers among the US population at risk and decedents. Standardized mortality ratios and quotients of standardized mortality ratios were used to estimate mortality risks.

RESULTS

Generally, during the period from 1966 through 1986, mortality rates in the United States for most causes of death declined among all smoking groups. However, mortality rates from respiratory diseases increased for current and former smokers.

CONCLUSIONS

The reported changes in never and current smoker mortality risks are similar in magnitude and direction to those reported in a previous study based on longitudinal data. The use of combined data from the National Mortality Followback Survey and the National Health Interview Survey offers several advantages as an epidemiological tool.

Linear extrapolation models of lung cancer risk associated with exposure to environmental tobacco smoke

This paper presents a model to estimate the number of lung cancer deaths due to ETS exposure among the 1992 U.S. never-smoking population, based on downward linear extrapolation from the estimated risks of active smokers. The model uses several recently available data sources including an extensive review of the published literature on indoor concentration of ETS constituents measured under real-world conditions and data from the National Mortality Followback Survey and the National Health Interview Survey which furnish nationally representative estimates of the distribution of the U.S. population and the persons who died from lung cancer by sex, age, and smoking status. The linear extrapolation model estimates that five male and six female excess lung cancer deaths due to ETS exposure would be expected in the 1992 U.S. population of over 52 million never smokers age 35 and over. Explanations for differences between the results of our downward extrapolation model and those of others are presented.

An alternative explanation for the apparent elevated relative mortality and morbidity risks associated with exposure to environmental tobacco smoke

Insofar as industrial and other blue collar workers are more likely to bring home toxic materials on their person, and also are more likely to smoke than those in other occupations, members of a household are more likely to be subject to paraoccupational exposure and belong to lower socioeconomic strata if the household contains a smoker than if the household does not contain a smoker. Thus observed differences in risk of mortality or morbidity ascribed to ETS on the basis of a comparison of households with and without smokers may be partly or entirely due to differences in paraoccupational exposure and socioeconomic strata. Similarly, differences in mortality and morbidity ascribed to paraoccupational exposure may be partly or entirely due to differences in ETS exposure that are also related to social class and to types of occupation. Unfortunately, there are no data now in existence that could help determine separately the effects of these major confounded variables. There exists, then, a situation in which two explanations are advanced for respiratory diseases among members of a household, each based on similar study populations but focused on different major risk variables: ETS on the one hand, socioeconomic status and paraoccupational exposure on the other. Properly focused investigations need to be initiated.