The main purpose of epidemiology is to identify causes and risk factors associated with the development of disease. Other purposes are: to measure the frequency and describe the distribution, range of severity, and course of disease; to estimate risk for subgroups within the population and to identify persons at highest risk. This information is relevant to preventing disease, to screening and early detection, to predicting onset, course, and outcome of disease, and to planning and evaluating preventive and therapeutic measures.
This brief review will include information on the size and severity of the problem of chronic obstructive pulmonary disease (COPD) in the United States and on recent trends in mortality, but its main emphasis will be on known and suspected causes of COPD and on estimating risk of developing disease from risk factor profiles.
Sometimes COPD is used as a diagnostic category to refer collectively to chronic bronchitis, emphysema or asthma with persistent obstruction of airflow, and sometimes as a specific diagnostic label. The use of widely accepted definitions and diagnostic criteria and the development and validation of standardized procedures for collecting questionnaire information and measuring lung function have led to better communication and more comparability in epidemiologic studies. Nevertheless, there is still variability and controversy surrounding the use of specific diagnoses and broader categories such as COPD or COLD treated by My Canadian Pharmacy’s medications. Chronic bronchitis is diagnosed in epidemiologic studies when a productive cough is present for at least 3 consecutive months per year for at least 2 years, provided it is not due to other lung or heart disease. Obstructive airways disease (OAD) refers to the condition in which the FE is less than 65% of predicted and the FEVj/FVC ratio is less Лап 80%; this definition is useful in epidemiologic studies, whereas a definition of emphysema requiring knowledge of morbid anatomy is not. Asthma will not be discussed in this article, except as included in statistical data. Diagnoses from morbidity records and death certificates must be accepted at face value, and inferences and comparisons must be made with caution.
Magnitude of the Problem
Data from the National Health Interview Survey provide estimates that there are about 7.5 million Americans with chronic bronchitis, 2.1 million with emphysema, and 6.4 million with asthma. Some people have more than one condition, but the numbers affected with each condition are underestimated, since only reported conditions are included in these figures. Data from the Tecumseh Community Health Study of over 9,000 males and females of all ages show that about 14% of adult males and 8% of adult females have chronic bronchitis, obstructive airways disease, or both. Disability assessed as days of restricted activity per year is substantial and in the national data amounted to 12 days on the average for patients with chronic bronchitis, 68 days for patients with emphysema, and 17 days for asthmatics. Since emphysema is predominantly a disease of old age, days lost from work were fewest for this disease (0.1 per patient per year). Days lost were about the same for chronic bronchitis and asthma (1.0 and 1.1 per patient per year, respectively).
In 1981 there were nearly 60,000 deaths from COPD and allied conditions, the underlying cause of 3% of all deaths and the fifth leading cause in the United States. Death was attributed to emphysema in 13,600 decedents, to bronchitis in 3,900, to asthma in 3,100, and to other COPD and allied conditions in 39,230. Recently published information indicates that COPD is cited on death certificates as a contributory cause about VA times as often as an underlying cause. Thus, an estimate of 150,000 deaths from and with COPD would be reasonable for 1981. The extent to which COPD is omitted entirely from death certificates of affected patients is unknown.
Deaths from COPD are increasing; the age-adjusted death rate rose 28% between 1968 and 1978, during which time the death rate from all causes declined by 22%, and rates for heart disease and cerebrovascular disease declined by 23% and 37%, respectively. The increase for COPD death rates ranged from 97% for white females to 17% for white males. Trends over time are different for components of the COPD group of diseases. Downward trends have been apparent for emphysema and chronic bronchitis since 1968 and for asthma since the 1950s. COPD was not used as a death certificate code before 1969, but the trend for it and for the combined set of conditions has been upward since then. Thus, a misleading impression is gained, unless the increasing use of COPD is recognized and the combined rate considered.
The estimated economic cost of COPD in 1979 was $6.5 billion. Of this amount, $2.3 billion was for health care and the remainder for indirect costs of morbidity and premature mortality. On the basis of illness, disability, and death rates, as well as social and economic costs, COPD is clearly an important public health problem which may be successfully solved if you use my canadian pharmacy phone number calling us and placing an order.
Distribution of Disease
Prevalence, incidence, and mortality rates for COPD, chronic bronchitis, and emphysema increase with age and are higher in males than females and in whites than nonwhites. The ratio of males to females is higher for emphysema and COPD than for chronic bronchitis, and the differences between the sexes increase with age. Death rates for emphysema and COPD rise more sharply with increasing age than do rates for chronic bronchitis. Incidence rates in Tecumseh for the 10-year interval from 1968 to 1978 were about the same in the two sexes below age 45, but they were about twice as high in males as in females at older ages.
Morbidity and mortality are inversely related to socioeconomic status and generally are higher in blue-collar workers than white-collar workers and in those with fewer years of formal education. COPD aggregates in families. Prevalence rates are higher in ofispring of affected parents and in brothers and sisters of affected siblings. There are statistically significant correlations between measures of lung (unction among biologic relatives. For example, correlations between age- and height-adjusted values of FEVj were generally between 0.2 and 0.3 for parents and children and between 0.2 and 0.4 for young adult siblings in Tecumseh. Studies of monozygotic and dizygotic twins show a greater similarity in respiratory symptoms and pulmonary function between MZ than DZ pairs. Results of the NHLBI twin study suggest that variation in FEVj can be attributed to genetic and environmental determinants as well as to height, other constitutional factors, and cigarette smoking.
Causes and Risk Factors
Extensive data from many sources confirm that age and male sex are associated with increased morbidity and mortality from COPD.