Watch the air pollution

People who live in areas with ‘bad air’ and smokers have an increased risk of developing chronic obstructive pulmonary disease (COPD). COPD affects over 600 million people worldwide and this represents about 10% of adults 40 years or older. In many Western countries, COPD is the leading cause of medical hospitalization. In 1990, COPD was the sixth most common cause of death worldwide. However, it is predicted that COPD will become the third most common cause by 2020.

As COPD patients have an underlying lung disease / injury, one would expect lung related conditions to be the main cause of morbidity and mortality. In the community, > 80% of COPD cases are mild to moderate COPDs [Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages 1 and 2]. For these individuals, the leading cause of morbidity is actually cardiovascular disease (CVD) and not lung related problems. The leading cause of mortality COPDs is lung cancer (Curr Opin Pulm Med 2008; 14: 115 – 121).

Why is CVD more common if you have COPD? While the exact reasons are not known, two mechanisms have been postulated. An underlying neuro-humoral disturbance leads to excess sympathetic nervous activity. This raises the resting heart rate and increases the risk of arrhythmias (abnormal heart rate) as seen in COPD patients. Apart from lung inflammation, COPD patients also have evidence of systemic inflammation. Using C-reactive protein (CRP) level as a biomarker of inflammation, the Lung Health Study (LHS) examined the risk of all-cause and CVD mortality over 7 years of follow up in a COPD-specific cohort. The study found that, compared to the group with the lowest CRP level, the CVD mortality risk was 1.8 times higher for the highest CRP group. In the same study, the leading cause for hospitalization for this cohort of patients was CVD and the leading cause of mortality was lung cancer. Nearly half of all hospitalizations and 22% of all deaths were due to CVD. Lung cancer accounted for 33% of all deaths. Interestingly, only 8% of this study population died from respiratory failure.

In general, COPD is associated with an increased risk of lung cancer. Mild COPD (Gold stage 1) is associated with a 50% increase, moderate COPD (GOLD stage 2) 2.1 fold increase and severe COPD 2.7 fold increase, independent of the effects of smoking. Smoking further amplifies this risk and smoking cessation reduces this risk. However, smoking cessation never returns the risk to that of non-COPD subjects. Even if you have never smoked but you have developed COPD, your risk of lung cancer death is increased by 2.4 fold.

The race to being ‘developed’ has brought with it increased industrialisation, increased construction and increased consumption. In developed countries, the societal desire to stay ahead means ever more construction and consumption. Unfortunately, the inevitable consequence of all these activities is air pollution. As an individual, if you live in an environment with persistent air pollution, you are not able to stop these polluting activites around you. However, you can at least help yourself by not smoking. A small but worthwhile consolation.