**3. Epidemiology**

118 Chronic Obstructive Pulmonary Disease – Current Concepts and Practice

Asthma

COPD and its various subsets have been known in human history since pre-industrialisation era. (Snider, 1992 as cited in Shapiro SD,2010). Badham is known to have first used of the term "chronic bronchitis" in 1808(Badham,1808 as cited in Shapiro SD,2010 ). Fletcher and Laennec have presented early reviews and studies in 18th and 19th century (Fletcher et al.,1976;Laennec,1835 as cited in Shapiro SD,2010). Reid demonstrated increased mucus gland size in his pathologic studies and led to the development of the "Reid Index" and

Ruysch described enlarged respiratory air spaces on the surface of human lungs in 1691(Ruysch,1691 as cited in Shapiro SD,2010). Over the next centuries, work of Matthew Baillie, Laennec and Gough helped in describing the pathologic enlargement of airspaces and classified it between centriacinar emphysema and panacinar emphysema(Baillie,1799,1808,Gough,1952;Laennec,1835 as cited in Shapiro SD,2010). Various "hypothesis" were proposed over the years to describe the disease pathogenesis:

i. "Dutch hypothesis" - originated by Orie(Netherlands) proposed that asthma and airway hyperreactivity leads to fixed airflow limitation. (Orie et al.,1961 as cited in

ii. "British hypothesis" - suggested the concept that mucus hypersecretion led to airway remodeling and airflow limitation.(Fletcher,1976 as cited in Shapiro SD,2010)

Fig. 1. Schematic Venn diagram of subsets of COPD. This is a non-proportional Venn diagram adapted from *Am J Respir Care Med* (ATS,1995) showing subsets of patients with chronic bronchitis, emphysema, and asthma(circles) and their relationship to airflow obstruction (box). The subsets comprising COPD are 4,5,6,7,8 and 9. Asthma is depicted by subset 3, whose airflow obstruction is completely reversible and are not considered to have

3

**C O P D**

7 8 9

<sup>4</sup> <sup>5</sup> <sup>6</sup>

gases."(GOLD,2006)

COPD.

**2. Historical background** 

Shapiro SD,2010)

Chronic Bronchitis

highlighted the anatomic basis for chronic bronchitis(Reid,1960).

1

that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or

Emphysema

2

Airflow Obstruction

COPD is a major public health problem with a high and continually increasing morbidity. The Burden of Obstructive Lung Disease (BOLD) study showed that the worldwide prevalence of COPD (stage II or higher) was 10.1%. This figure varied by geographic location and by sex with prevalence among men at 11.8% (8.6-22.2%) and among women at 8.5% (5.1-16.7%)(Buist et al.,2007). The wide differences noted was partly due to site and sex differences in the prevalence of smoking. The true prevalence is likely higher because COPD is both under-recognized and under-diagnosed. COPD was the sixth leading cause of death worldwide in 1990 and is expected to become the third leading cause of death by 2020(Murray & Lopez,1997 as cited in Shapiro SD,2010).

COPD has higher prevalence in low-socioeconomic population(Fletcher,1976). Commonly, patients present in their fifth decade of life with productive cough or acute chest illness. Alpha-1 Protease Inhibitor (A1PI) deficient patients present earlier than other COPD patients in 3rd-4th decade of life. COPD progresses with age and is more prevalent in elderly populations. In the United States, 15% of the total population aged 55 to 64 will have moderate COPD (GOLD stage 2, FEV1 < 80% predicted), and this increases to over 25% for those older than 75(Stockley et al.,2009 as cited in Shapiro SD,2010).
