Heat waves: The silent epidemic

  • The study has been authored by  Dileep Mavalankar, director Indian Institute of Public Health, Gandhinagar (IIPHG).
The India meteorology department (IMD) has forecasted that this summer is going to be very hot.(HT Photo)
The India meteorology department (IMD) has forecasted that this summer is going to be very hot.(HT Photo)
Published on May 12, 2022 11:43 AM IST
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ByHindustan Times

As we get out of Covid pandemic, people are weary of further waves of it. People want to get on with their lives. Fortunately, as of now the possibility of 4th wave of covid pandemic seems remote. Even it comes it will be mild given our high vaccination rate and high past infection related immunity. But here I want to alert the readers to a new and looming but silent epidemic of massive proportion which is eminent. The epidemic of Heat wave related morbidity and mortality this summer. 

The India meteorology department (IMD) has forecasted that this summer is going to be very hot. March which is traditionally a month of spring in India has registered recording breaking average maximum temperatures. This March was hottest in last 122 years of the IMD history. This March heat was not only reported in India but in many parts of the world. The South and North Pole recorded 40 and 30 degrees higher temperatures than normal for March. This is a shocker. In India April is also turning out to be much hotter than usual this year. Several parts India have had heat waves and heat wave warnings are on in several parts of the country.  The IMD has done its job, now the government and especially health and other departments and general administration has to take steps to reduce the impact of increasing heat on human, animal and plant health. 

It is well documented and also understood by the community that heat waves can kill. Heat stroke is well recognised medical condition. If one is affected by heat stroke, chances of death could be as high as 30% in spite of treatment. Hence preventing heat stroke is very vital. But what is not well understood by lay people, government, media and even medical professionals is that the deaths reported in government and in media a like proverbial “tip of the Iceberg”. Meaning there by that only 10% of actual heat wave related deaths get reported and 90% of such deaths are not reported or counted.  This happens even in western countries good registration of deaths. The reason for this is that there are two types of heat strokes – Exertional heat stroke which happens when a person is doing heavy work in direct sun light during very hot temperature. This is the typical commonly understood heat stroke. But much more frequent type of heat stroke (90%) is non-exertional heath stroke. This happens to people who are old and having comorbidities who are not in direct sun light but at home or office, during a heat wave.  Heat stroke is when the body gains too much heat from outside with or without additional internal heat due to exertion, so that the temperature regulatory centers of the brain get dysfunctional or deranged causing excessive heating of the body and inability to cool via sweat. 

Non-exertional heat stroke is generally seen presenting in old, morbid person coming to emergency department during heat wave with heart, circulatory, respiratory or kidney failure. As the patient does not have history of working in hot sunlight the doctors do not register this as heat stroke but it is treated as major organ failure case. When such as care dies it is also not correlated and entered as death due to heat stroke or heat wave. Such mortality due to heat wave can be easily captured if the cities and districts count all-cause mortality on daily basis and compare with average daily mortality in summer for the past five years. This is exactly what was done in heat waves of Chicago in 1995, in Europe in 2003 and by us in Ahmedabad 2010. Our work in Ahmedabad heat wave on 2010 showed that in single heat wave of one week from 20-26th May lead to 800 additional deaths due to all causes. But there were only 76 heat stroke deaths reported from five major hospitals of the city. This clearly showed that if we only capture reported heat stroke deaths we will miss a majority of heat related deaths. Hence it is urgently needed to measure daily mortality in each major city during April, May and June this year and compare it with average daily mortality in that city during summer. Ahmedabad data from 2010 showed that then the city had 100 daily deaths due to all causes as an average figure for month of May. But on  May 21, 2010 when the temperature in Ahmedabad touched 47 Deg C the total death reported on that day were 310. I am sure that such massive increase in mortality are happening in each major city facing heat waves, but due to lack of system to report and analyse daily death we are not capturing the true impact of heat waves on human health. NDMA and home ministry must mandate such analysis in all 1000 major cities where IMD heat predictions are available.  This will help measure real loss due to heat waves.

We also have shown in Ahmedabad city that if heat action plans are implemented then such heat wave related mortality can decline by 30-40% during peak of heat waves. Such plans have four pillars. Heat wave prediction and alert system, public awareness, preparation of health services and long-term measure to reduce heat and increase resilience. This plan is being promoted by NDMA and they are reviewing implementation of the states. States should establish environmental health cell under which the implementation of heat action plan can be taken up in right earnest. Guide lines for such implementation are also available. 

Unless we take the IMD predictions seriously take immediate actions on heat waves we may lose many citizens to the upcoming heat waves. It is time that all stakeholders act with coordination and determination to ensure that no one dies of heat wave this summer. As explained above the heat wave deaths are very insidious and hence thousands may die due to heat wave without being recorded as such. 

The study has been authored by Dileep Mavalankar, director Indian Institute of Public Health, Gandhinagar (IIPHG))







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