Heat waves: the silent epidemic


As we emerge from the Covid pandemic, people are tired of new waves. People want to get on with their lives. Fortunately, as of now, the possibility of a 4th wave of the covid pandemic seems remote. Even if that happens, it will be mild given our high vaccination rate and high immunity from past infections. But here I want to alert readers to a new impending but silent epidemic of massive proportions that is eminent. The epidemic of morbidity and mortality linked to the heat wave this summer.

The Indian Department of Meteorology (IMD) predicted that this summer is going to be very hot. March, which is traditionally a spring month in India, saw record average maximum temperatures. This March was the hottest in 122 years in IMD history. This March heat has not only been reported in India, but in many parts of the world. Both the South Pole and the North Pole recorded temperatures 40 and 30 degrees above normal in March. It’s a shock. In India, April is also turning out to be much hotter than usual this year. Several parts of India have experienced heat waves and heat wave warnings are underway in several parts of the country. IMD has done its job, now the government and especially health and other ministries and general administration must take action to reduce the impact of increased heat on human, animal and plant health.

It is well documented and also understood by the community that heat waves can kill. Heatstroke is a well-known medical condition. If a person is affected by heat stroke, the risk of death can reach 30% despite treatment. Therefore, the prevention of heatstroke is very important. But what is not well understood by lay people, government, the media and even medical professionals is that deaths reported to government and media are like the proverbial “tip of the iceberg”. . This means that only 10% of actual heat wave deaths are reported and 90% of those deaths are not reported or counted. This happens even in western countries with good death registration. The reason for this is that there are two types of heat stroke – Exertional heat stroke which occurs when a person does heavy work in direct sunlight at a very hot temperature. This is the commonly understood typical heat stroke. But the most common type of heat stroke (90%) is effortless heat stroke. It happens to older people and those with comorbidities who are not in direct sunlight but at home or in the office, during a heat wave. Heat stroke occurs when the body receives too much heat from the outside with or without additional internal heat due to exertion, such that temperature regulation centers in the brain become dysfunctional or deranged, causing overheating of the body and an inability to cool down through perspiration.

Stressless heat stroke usually presents in a morbidly elderly person presenting to the emergency room during a heat wave with cardiac, circulatory, respiratory, or renal failure. As the patient has no history of working in direct sunlight, doctors do not register it as heat stroke, but it is treated as a case of major organ failure. When such care dies, it is also not correlated and entered as death due to heat stroke or heat wave. This heat wave mortality can be easily captured if cities and districts tally all-cause mortality daily and compare it to the average daily mortality in summer over the past five years. This is exactly what was done in the heat waves in Chicago in 1995, in Europe in 2003 and by us in Ahmedabad in 2010. Our work on the heat wave in Ahmedabad in 2010 showed that a single wave week-long heat from May 20-26 led to 800 additional deaths from all causes. But only 76 heat stroke deaths have been reported at five major hospitals in the city. This clearly showed that if we only capture reported heatstroke deaths, we will miss the majority of heat-related deaths. It is therefore urgent to measure the daily mortality in each major city in April, May and June of this year and compare it to the average daily mortality in that city during the summer. Data from Ahmedabad from 2010 showed that the city then had 100 daily deaths from all causes on average for the month of May. But on May 21, 2010, when the temperature in Ahmedabad reached 47 degrees Celsius, the total number of deaths reported that day was 310. I’m sure such a massive increase in mortality is happening in every major city facing to heat waves, but due to the lack of a system to report and analyze daily deaths, we do not understand the true impact of heat waves on human health. NDMA and the Home Office are to commission such an analysis in the 1000 major cities where IMD heat forecasts are available. This will make it possible to measure the real losses due to heat waves.

We have also shown in the city of Ahmedabad that if heat action plans are implemented, heat wave related mortality can decrease by 30-40% during peak heat waves. These plans are based on four pillars. Heat wave forecasting and warning system, public awareness, health service preparedness and long-term measure to reduce heat and increase resilience. This plan is being promoted by the NDMA and they are reviewing the states implementation. States should establish an environmental health cell where the implementation of the heat action plan can be taken seriously. Guidelines for such implementation are also available.

Unless we take IMD’s predictions seriously and take immediate action against heat waves, we could lose many citizens to future heat waves. It is time for all actors to act with coordination and determination to ensure that no one dies from the heat wave this summer. As explained above, deaths caused by heat waves are very insidious and therefore thousands of people can die from heat waves without being registered as such.

The study was authored by Dileep Mavalankar, Director of the Indian Institute of Public Health, Gandhinagar (IIPHG))


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