<strong>GOLD</strong>_WR_05 8/18/05 12:56 PM Page 19 CHAPTER 3 RISK FACTORS
<strong>GOLD</strong>_WR_05 8/18/05 12:56 PM Page 20 CHAPTER 3: RISK FACTORS KEY POINTS: • Risk factors <strong>for</strong> COPD include both host factors and environmental exposures, and the disease usually arises from an interaction between these two types of factors. • The host factor that is best documented is a rare hereditary deficiency of alpha-1 antitrypsin. Other genes involved in the pathogenesis of COPD have not yet been identified. • The major environmental factors are tobacco smoke, occupational dusts and chemicals (vapors, irritants, fumes), and indoor/outdoor air pollution. INTRODUCTION The identification of risk factors is an important step toward developing strategies <strong>for</strong> prevention and treatment of any disease. Identification of cigarette smoking as an important risk factor <strong>for</strong> COPD has led to the incorporation of smoking cessation programs as a key element of COPD prevention, as well as an important intervention <strong>for</strong> patients who already have the disease. However, although smoking is the best-studied COPD risk factor, it is not the only one. Further studies of other risk factors could lead to similar powerful interventions. Much of the evidence concerning risk factors <strong>for</strong> COPD comes from cross-sectional epidemiological studies that identify associations rather than cause-and-effect relationships. Although several longitudinal studies (which are capable of revealing causal relationships) of COPD have followed groups and populations <strong>for</strong> up to 20 years, none of them has monitored the progression of the disease through its entire course. Thus, current understanding of risk factors <strong>for</strong> COPD is in many respects incomplete. Figure 3-1 provides a summary of risk factors <strong>for</strong> COPD. The division into "Host Factors" and "Exposures" reflects the current understanding of COPD as resulting from an interaction between the two types of factors. Thus, of two people with the same smoking history, only one may develop COPD due to differences in genetic predisposition to the disease, or in how long they live. Risk factors <strong>for</strong> COPD may also be related in more complex ways. For example, gender may influence whether a person takes up smoking or experiences certain occupational or environmental exposures; socioeconomic status may be linked to a child's birth weight; longer life expectancy will allow greater lifetime exposure to risk factors; etc. Understanding the relationships and interactions among risk factors is a crucial area of ongoing investigation. Host Factors Exposures Figure 3-1. Risk Factors <strong>for</strong> COPD • Genes (e.g., alpha-1 antitrypsin deficiency) • Airway Hyperresponsiveness • <strong>Lung</strong> Growth • Tobacco Smoke • Occupational Dusts and Chemicals • Indoor and Outdoor Air Pollution • Infections • Socioeconomic Status The best-documented host factor is a severe hereditary deficiency of alpha-1 antitrypsin. The major environmental factors are tobacco smoke, occupational dusts and chemicals (vapors, irritants, fumes), and indoor and outdoor air pollution. However, it is very difficult to demonstrate that a given risk factor is sufficient to cause the disease. Data are not available to determine whether the increasing prevalence of respiratory symptoms and the accelerated rate of lung function decline that occur with age reflect the cumulative exposure to respiratory particles, irritants, fumes, vapors, etc., or host-related phenomena such as the loss of elastic recoil of lung tissue and stiffening of the chest wall. The field of normal lung aging has been only minimally explored and more work is required. The role of gender as a risk factor <strong>for</strong> COPD remains unclear. In the past, most studies showed that COPD prevalence and mortality were greater among men than women 1-4 . More recent studies 5,6 from developed countries show that the prevalence of the disease is almost equal in men and women, which probably reflects changing patterns of tobacco smoking. Some studies have in fact suggested that women are more susceptible to the effects of tobacco smoke than men 4,7 . This is an important question given the increasing rate of smoking among women in both developed and developing countries. The role of nutritional status as an independent risk factor 20 RISK FACTORS
![Di Bari [NO].pdf - GOLD](https://img.yumpu.com/21544924/1/190x143/di-bari-nopdf-gold.jpg?quality=85)
Change language