About half of all Chronic Obstructive Pulmonary Disease (COPD) cases worldwide are due to non-tobacco-related risk factors, experts have said.

In a new series in the Lancet Respiratory Medicine, Pune-based expert Sundeep Salvi along with co-authors have called for promoting early diagnosis to help mitigate the repercussions of COPD in the “never-smokers”.

COPD is a progressive lung disease characterised by respiratory symptoms associated with chronic airflow limitation that affects an estimated 300 million people globally. It is the third leading cause of death worldwide, with about 3.2 million people dying from the ailment annually. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) definition states that COPD is “usually caused by significant exposure to noxious particles or gases”.

Although cigarette smoking has traditionally been considered the most frequent and important cause of COPD, other factors are increasingly been recognised worldwide.

“Obtaining accurate estimates of COPD prevalence is challenging, particularly given the use of different criteria to define COPD, and the marked variation in prevalence estimates in both smokers and never-smokers underlines this difficulty,” researchers Ian A Yang and Christine R Jenkins said in the series published online on Tuesday, April 12.

Factors such as low levels of clinical suspicion and testing, rurality, low socioeconomic status, low education and health literacy levels, and variations in non-tobacco exposures — all of which might be associated with considerable underdiagnosis of COPD in never-smokers — add to the challenge of accurately quantifying COPD prevalence in never-smokers, the researchers said. A compounding factor is that awareness of COPD is very low in underprivileged areas, as shown by a community survey in urban slums and rural areas around Pune city, Dr Salvi added.

About half of all COPD cases worldwide are due to non-tobacco-related risk factors, according to the researchers. Risk factors for COPD in never-smokers include exposure to household biomass smoke, outdoor air pollution, occupational exposures to dust and fumes, poorly controlled asthma, environmental tobacco smoke, history of pulmonary tuberculosis, recurrent respiratory tract infections, and low socioeconomic status. These non-tobacco-related factors disproportionately affect women.

Dr Salvi also pointed out that impaired lung growth during childhood, with lack of attainment of maximal lung size and low baseline lung function, is associated with an increased risk of COPD.

A range of biological mechanisms is involved in the development of COPD in never-smokers, with distinct cellular features and molecular pathways for specific risk factors. Never-smokers with COPD have milder chronic respiratory symptoms and airflow limitation than their smoking counterparts but still have a poor prognosis with an increased risk of exacerbation. Research is urgently needed to develop a strong evidence base for the management of COPD in never-smokers, the researchers stressed.

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