DEFINTION, PHENOTYPES AND EPIDEMIOLOGY

By:Dr. SURABI SUSHMA REDDYPOST GRADUATE(PULMONOLOGY)

DEFINITION• GOLD guidelines 2011 defined COPD as “it is a common preventable and treatable

disease, characterized by persistent airflow limitation that is usually progressive and is not fully reversible and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases. Exacerbations and comorbidities contribute to the overall severity in individual patients.”

• GOLD guidelines 2017 modified the definition of COPD as follows:

“ it is a common preventable and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities usually caused by significant exposure to noxious particles or gases.”

• The chronic airflow limitation that is characteristic of COPD is caused by mixture of small airways disease (e.g., obstructive bronchiolitis) and parenchymal destruction (emphysema) , the relative contribution of which may vary from person to person.

chronic inflammation

narrowing of small airways and lung parenchyma destruction

loss of alveolar attachments to small airways

reduced lung recoil

decreased ability of airways to remain open during expiration.

• Diagnostic criteria of COPD according to GOLD 2013 is

“COPD should be considered in any patient who has dyspnoea, chronic cough or sputum production, and a history of exposure to risk factors for the disease. Spirometry is required to make the diagnosis in this clinical context; the presence of a post-bronchodilator FEV1/ FVC < 0.70 confirms the presence of persistent airflow limitation and thus of COPD.”

• Airflow limitation is a reduction in velocity of expiratory airflow, consisting of low FEV1 and low FEV1/FVC despite bronchodilator therapy.

• Airflow reversibility is an increase in FEV1 of 200ml and 12% improvement greater than baseline FEV1 after bronchodilator therapy.

• Airflow reversibility has been found not to influence the sensitivity or specificity to diagnose COPD and so GOLD guidelines do not recommend the use of airflow reversibility as criterion for the definition of COPD.

PHENOTYPES• For COPD, phenotypes is almost synonymous

with clinical subgroup.• COPD phenotype is defined as a single or

combination of disease attributes that describe differences between individuals with COPD as they relate to clinically meaningful outcomes (symptoms, exacerbations, response to therapy, rate of disease progression, or death.)

• Different phenotypes in COPD: chronic bronchitis emphysema asthma bronchial hyperresponsiveness bronchodilator reversibilty hyperinflation cachexia frequent exacerbations systemic inflammation.

• CHRONIC BRONCHITIS is defined as presence of a chronic cough on most days for 3months in each of two consecutive years, in a patient in whom other causes of chronic cough have been excluded.

• EMPHYSEMA is abnormal, permanent enlargement of the distal airspaces, distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis

• ASTHMA is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or early in the morning. These episodes are usually associated with widespread, but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment.

• Frequent exacerbator can be defined as having 2 or more exacerbations per year.

• Systemic inflammation can be measured by certain biomarkers like CRP, fibrinogen and WBC count which helps in prognosis.

Asthma COPD overlap syndrome:

• As significant overlap exists among different types of COPD, many patients have bronchial inflammation with features of both asthma and chronic bronchitis/emphysema.

• GOLD and GINA defined ACOS as “characterized by persistent airflow

limitation with several features usually associated with asthma and several features associated with COPD.”

EPIDEMIOLOGY• PREVALENCE: based on BOLD and other epidemiological studies, it is estimated

that total number of COPD was 384million in 2010 with global prevalence of 11.7% with around 3million deaths annually.

• With increasing prevalence of smoking in developing countries and aging population, the burden of COPD may rise and by 2030 there may be 4.5million deaths annually from COPD and related conditions.

• In developed countries, there exists prevalence of 8% to 10% among adults 40years of age or older.

• MORBIDITY: includes physician visits, emergency

department visits and hospitalizations. Data regarding COPD less readily available and less reliable and is usually affected by other concomitant chronic conditions.

• In 2005, COPD was the 8th leading cause of loss of DALYs across the world but ranked 5th in 2013 of DALYs lost.

• MORTALITY deaths from COPD or chronic airway obstruction are included in

broad category of “COPD AND ALLIED CONDITIONS” in ICD-10.• Under recognition and under-diagnosis of COPD reduces the accuracy

of mortality rate.• Increase in COPD related mortality can be attributed to the

expanding epidemic of smoking, reduced mortality from other common causes of death(IHD, ID), the aging of world population particularly in high income countries and scarcity of effective disease modifying therapies.

• There occurs to be a trend of increasing mortality among women.

• ECONOMIC BURDEN: in the EU, total direct costs of respiratory

disease are estimated to be about 6% of total health care budget, with COPD accounting for 56% of the cost of respiratory disease.

• There is a striking direct relationship between severity of COPD and cost of care and the cost distribution changes as the disease progresses.

• SOCIAL CLASS: there is a strong association between social

deprivation in childhood, particularly domestic overcrowding and ventilatory capacity and cough , suggesting that conditions in early life influence the development of chronic respiratory disease in adulthood.

• In developed countries, the prevalence might have plateaued but there is an increasing prevalence in developing countries due to additional biomass exposure.

Prevalence of COPD and gender differences:

• COPD was historically considered a disease of male predominance but nevertheless, there occurred a significant shift in the gender prevalence.

• But in developing countries, the prevalence of COPD is still higher in men when compared to women.

• Women are more susceptible to effects of tobacco smoke than men leading to a more severe form of disease for equivalent quantity of cigarettes consumed.

• There is greater burden of small airways diseases in women compared to men with COPD with a similar history of tobacco smoke exposure.

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