People training for the Half Marathon are at risk of acute cardiovascular events

People training for the Half Marathon are at risk of acute cardiovascular events

Dr KK Aggarwal

The Indian Medical Association (IMA) has called for the immediate cancellation of the Airtel Delhi Half Marathon to be held on Sunday, November 19, 2017 at 7.00 a.m. because of the prevailing ‘very poor’ to ‘severe’ air quality in the Delhi-NCR region. The AQI in many areas in the national capital has crossed 999. This is a public health emergency.

Runners or those who exercise outdoors in conditions of air pollution are especially at a greater risk of inhaling toxic air pollutants.

Some physiological changes that occur during exercise may aggravate the harmful effects of air pollution on health. Breathing becomes faster and deeper during exercise or running. The increased respiratory minute ventilation means people inhale more of toxic pollutants. Changeover to mouth breathing from nasal breathing means the nasal filtration mechanism is bypassed. Exercise practice in polluted outdoor environment, over a period of 5 days, impairs nasal mucociliary clearance in young healthy amateur runners. (J Breath Res. 2016 Dec 21;10(4):046018). As a result of the reduced nasal mucociliary clearance, more air pollutants are absorbed instead of being cleared by the respiratory system (Br J Sports Med. 2001 Aug;35(4):214-22). Because of the increase in airflow velocity, pollutants travel much deeper into the airways, which further adds to the amount of pollutants inhaled.

Air pollution also has a significant negative effect on performance of the athletes. PM10 has a significant correlation with reduced performance in marathon runners. Under normal breathing conditions, PM10 is filtered through the nose. But, because of mouth breathing during exercise, PM10 is not removed and is instead inhaled in large amounts (Med Sci Sports Exerc. 2010 Mar;42(3):585-91).

Air pollution is a well-recognized health hazard. And, exercising under conditions of high pollution thus may have disastrous health consequences, even for the healthy participants. In healthy individuals, it can cause cough or breathlessness on exertion. In asthmatics, air pollution can trigger off an acute asthma attack. In COPD patients, it can worsen their disease. Air pollution can precipitate heart attack or stroke in patients with known heart disease or those who are at risk of heart disease. It can also increase the risk of sudden cardiac death.

People who are training for the marathon are thus at risk of acute cardiovascular or respiratory events, which may potentially be life-threatening.

In September 2015, it was reported that six runners and one race official suffered heart attacks during 2105 Beijing Marathon. About 30,000 runners participated in the marathon. Shortly after the fastest runners were finishing, the US embassy in Beijing recorded an Air Quality Index (AQI) of 175. It classes levels between 151 and 200 as "unhealthy" and advises people to "reduce prolonged or heavy exertion" during such periods. In the 2014 Beijing Marathon too, the runners participated in the event with a blue warning (air quality is unsuitable for outdoor activities) for air pollution issued by the government (http://www.scmp.com/news/china/society/article/1859890/six-runners-and-race-official-suffer-heart-attacks-during-beijing).

AQI	Air quality	Health implications for healthy people
0-50	Excellent	No health implication
51-100	Good	No health implication
101-150	Slightly polluted	Slight irritation may occur. Avoid marathon
151-200	Moderately polluted	Reduce strenuous outdoor exercises, No sports, No Marathon or Cyclathon, No Cricket matches
201-300	Severely polluted	Reduce outdoor activities in schools and others, no cycling, no jogging, no running. Prolonged exposure can harm lung and heart patients.
>300	Heavily polluted	Avoid outdoor activities, No long walks. Prolonged exposure can cause lung injury
>400	Hazardous	Reduce indoor activities and even ordinary walks should be restricted. The health impacts may be experienced even during light physical activity.