Morning MEDtalks with Dr KK Aggarwal 15th October 2018

Harm reduction refers to ways that people try to mitigate the dangers or harms associated with a particular act. For instance, giving people who inject drugs access to clean needles is a harm reduction strategy because it reduces the HIV and hepatitis C risk associated with drug use given the possibility of sharing needles. Just as clean needles help drug users to avoid infections, vaping can help cigarette smokers to steer clear of health risks such as cancer by reducing how much they smoke. More than 70 nicotine specialists appealed to the World Health Organisation (WHO) to include vaping as a recommended harm reduction method in the WHO’s tobacco control guidelines.

The number of babies born in India through caesarean section increased from 9% in 2005-6 to 18.5% in 2015-16, according to a series of three papers published in The Lancet journal, which also found that C-section use almost doubled worldwide between 2000 and 2015.

Weather and marathon

Air temperature≤8 °C improved (p<0.001) race times compared to air temperature>8°C. Precipitation (>0 mm) improved performance for the annual 100 fastest and annual 10 fastest (p=0.013-0.031) but not for all finishers (Int J Sports Med. 2018 Oct 5).

The air pollutant concentrations of carbon monoxide, ozone, particulate matter smaller than 10 microm (PM(10)), PM(2.5), nitrogen dioxide, and sulfur dioxide ranged from 0 to 5.9 ppm, from 0 to 0.07 ppm, from 4.5 to 41.0 microg x m(-3), from 2.8 to 42.0 microg x m(-3), from 0 to 0.06 ppm, and from 0 to 0.05 ppm, respectively. After adjusting for WBGT-associated performance decrements, only PM (10) was associated with decrements in performance of women. For every 10-microg x m (-3) increase in PM (10), performance can be expected to decrease by 1.4% (Med Sci Sports Exerc. 2010 Mar;42(3):585-91).

Extreme temperatures, lightning in the event vicinity, strong winds, and poor air quality are factors that put participants at risk and are reasons for cancellation.

Poor air quality can adversely affect race participants with asthma or other pulmonary disorders, and is more of an issue in particular parts of the world. Air-quality guidelines are based on the air quality index (AQI), which reflects the particulate and chemical matter in the air. As the AQI rises above 100 to 150, athletes and volunteers can be adversely affected [www3.epa.gov/airnow/aqi_brochure_02_14.pdf (Accessed on September 18, 2016). The AQI can be used to determine the need for event cancellation. If the AQI is above 100, it is prudent for race administrators to warn participants and volunteers, particularly those with lung conditions, about the potential risk.

Unseasonably warm weather, particularly for participants from cooler regions who may not be acclimated to the heat, increases the risk of heat-related medical problems [Sports Med 2007; 37:396, Med Sci Sports Exerc 2000; 32:1549, BMC Public Health 2014; 14:1109.].

Unforeseen natural events (e.g., lightning storm) or man-made catastrophes (e.g., Boston Marathon 2013 bombing) have caused cancellations of major events in past years.

When deciding whether to cancel or proceed with an event despite some increased risk (eg, temperatures higher or lower than anticipated), event organizers and the medical director must take into account the effect of the anticipated increase in the number of casualties on community medical capacity and care, in addition to the increased needs for on-site medical care.

For the Twin Cities Marathon, the medical committee has used race weather conditions and race outcomes data (non-finishers plus medical tent encounters per 1000 finishers) to establish a "do not start" temperature (WBGT of 20.5°C or 69°F) that is specific to the heat stress at the start of the race and community medical capacity [Med Sci Sports Exerc 2015; 47:1958.]. High temperatures and humidity during the 2007 Twin Cities Marathon pushed the emergency response system beyond its capacity to provide patient transport and medical care at race area hospitals, forcing the use of regional ambulance systems and hospitals outside the usual catchment area. Using data from that episode, race administrators subsequently calculated the "do not start" WBGT described above that is specific to the race and local medical system (the calculation, which incorporated a number of race data points to determine the interaction of casualties and area medical response capacity) [Med Sci Sports Exerc 2010; 42:226].

Cold temperatures do not generally cause increases in the rate of exercise-associated collapse or other medical issues, provided participants are appropriately dressed and trained for the event. Nordic ski races set temperature and wind-chill thresholds for cancellation to reduce the risk of frostbite (including corneal injury), particularly during the faster downhill portions of the course. The International Ski Federation set a cancellation level at -20°C (-5°F) following the 1980 Olympics. The "do not start" level has been lowered to -25°C (-13°F), with a requirement to notify the athletes of the increased risk for cold injury for temperatures of -20 to -24°C. Volunteers may be at greater risk in cool wet or extreme cold conditions than seasoned event participants due to lack of proper clothing.

Some increase in the risk to participants and volunteers occurs with wind speeds in excess of 32 mph (51 km/hour); risks accelerate with winds above 39 mph (63 km/hour).

In the United States, the National Weather Service issues a high wind warning when sustained wind speeds of at least 40 mph (64 km/hour) or gusts of 58 mph (93 km/hour) or more are expected or occurring.

Potential hazards stem from moving objects (start/finish banners, tents, tree limbs) and direct injury to race participants or personnel, especially those on bicycles. Higher wind speeds increase the wind chill, which raises the risk of hypothermia in participants and possibly frostbite if the ambient temperature is below freezing. Wind speeds can be predicted with reasonable accuracy, and information from a local or national weather service can be helpful. Event directors should consider wind speed in their race cancellation policy.

Air pollution and heart

Air pollution has emerged as a potentially modifiable risk factor for the development of heart disease. Multiple observational studies have demonstrated an association between fine particulate air pollution (primarily from the use of fossil fuels in automobiles, power plants, and for heating purposes) and cardiovascular and cardiopulmonary mortality as well as an increased risk for the development of acute coronary syndromes.

The Womens Health Initiative Observational study database of more than 65,000 postmenopausal women without prior CVD was used to evaluate the relation between a womans long-term exposure to air pollutants estimated by residential geocoding and the risk for a first cardiovascular event [N Engl J Med 2007; 356:447]. The principal findings were that for each 10 mcg/m3 increase in pollution concentration, there were significant increases in the risk of any cardiovascular event (hazard ratio [HR] 1.24), death from CVD (HR 1.76), and cerebrovascular events (HR 1.35).

Mortality data from nearly 450,000 patients in the American Cancer Society Cancer Prevention Study II database were correlated to geocoded air pollution data, including average concentrations of ozone and fine particulate matter (≤2.5 micrometers in diameter [PM2.5]) [N Engl J Med 2009; 360:1085]. In multivariate analysis, PM2.5 (but not ozone) concentration was significantly associated with the risk of death from cardiovascular causes (relative risk [RR] 1.2).

In the prospective MESA Air cohort study involving 6795 participants in six United States metropolitan areas, each increase in PM2.5 of 5 mcg/m3was associated with 4.8 Agatston units per year progression of coronary calcification [Lancet 2016; 388:696].

Further support for the significance of air pollution comes from a study of death rates in Dublin, Ireland before and after a ban on coal sales that led to a 70 percent reduction in black smoke concentrations [Lancet 2002; 360:1210]. Adjusted cardiovascular deaths fell by 10.3 percent in the six years after the ban.

Both the American Heart Association (2010) and the European Society of Cardiology (2015) have issued official statements discussing the association between long-term exposure to fine particulate air pollution and increased risk of developing CVD [Circulation 2010; 121:2331, Eur Heart J 2015; 36:83].

In addition to long-term risk, short-term exposure to air pollutants (both ozone and fine particulate matter) has been associated with total mortality [JAMA 2017; 318:2446] and acute coronary ischemic events [Circulation 2005; 111:563, Eur Heart J 2013; 34:1306., Lancet 2018; 391:339, Circulation 2006; 114:2443.]

In a case-crossover study of more than 22 million deaths between 2000 and 2012 identified from the United States Medicare population, increased risk of all-cause mortality was seen with short-term increases in fine particulate matter (RR increase 1.05 percent for each 10 mcg/m3 increase) and ozone (RR increase 0.51 percent for each 10 part per billion increase) [JAMA 2017; 318:2446.]. The increased risk occurred at levels of air pollution that are lower than the currently suggested air quality standards.

In a study of over 12,000 patients living in a defined geographic area, a short-term increase in fine ambient particulate matter positively correlated with an increase in acute ischemic coronary events [Circulation 2006; 114:2443].

In a systematic review and meta-analysis of data from 34 studies, carbon monoxide, nitrogen dioxide, sulfur dioxide, and small particulate matter (less than 10 microns and less than 2.5 microns) were all associated with an increased risk of acute heart attack with the overall population attributable risk ranging from 1 to 5percent [JAMA 2012; 307:713].

Possible mechanisms by which fine particulate air pollution may increase the risk of CVD include [Eur Heart J 2015; 36:83]: An increase in mean resting arterial blood pressure through an increase in sympathetic tone and/or the modulation of basal systemic vascular tone [Circulation 2002; 105:1534].

An increase in the likelihood of intravascular thrombosis through transient increases in plasma viscosity and impaired endothelial dysfunction [Circulation 2002; 106:933.] and the initiation and promotion of atherosclerosis [Circulation 2010; 121:2755, J Am Coll Cardiol 2010; 56:1803].

Air pollution and lungs

Changes in air pollution may well be relevant to increasing asthma prevalence in some areas. There is extensive evidence about the effects of vehicular pollution, including both the products of gasoline engines and diesel particulates, on allergic respiratory disease in areas such as Los Angeles.

There is a known correlation between levels of air pollution and lung disease, but the association between air pollution and asthma is less clear. As an example, in a study of six cities in the United States, there was a direct relationship between the levels of particulate pollution and reported rates of chronic cough and bronchitis [Am Rev Respir Dis 1989;139:587]. There was no association between particulate concentration and asthma, persistent wheeze, or hay fever. It is possible that asthma is related to specific pollutants, while other respiratory diseases are related to total air pollution.

East Germany had consistently high levels of SO2 and other particulates, whereas West Germany had low levels of sulfur dioxide (SO2) but slightly higher levels of nitrogen dioxide (NO2). The prevalence rates of asthma and atopy were higher in the West German towns, while the rates of bronchitis were higher in the East German towns, suggesting at most a minor effect of air pollution on the prevalence of asthma [Thorax 1993; 48:879, Am J Respir Crit Care Med 1994; 149:358].

Air pollution and sudden death

According to three studies, the rate of marathon-related sudden cardiac arrest ranges from 1.01 to 2.6 per 100,000 finishers, while mortality rates range from 0.63 to 1.3 per 100,000 finishers [N Engl J Med 2012; 366:130, Br J Sports Med 2013; 47:168, Med Sci Sports Exerc 2012; 44:1843]

Video to watch: TEDx Video: Doctor-patient relationship www.youtube(dot)com/ watch?v=i9ml1vKK2DQ

Dr KK Aggarwal

Padma Shri Awardee

President Elect CMAAO

President Heart Care Foundation of India