The iceberg of heat wave deaths

Does the title sound like a contradiction in terms? What we want to highlight is the poor understanding of heat wave-associated mortality in hot-climate countries such as India. The number of heat stroke deaths reported in 2018 to the National Disaster Management Authority (NDMA) was only about 25.

If it has indeed come down so drastically from the 2,200 reported in 2015, the credit must go to the Centre and state governments, and to the NDMA, which has put in a lot of effort to raise awareness of heat-wave related deaths and to develop action plans at city and district levels to prevent them.

Still, it is unrealistic to think that in a country of 1.3 billion people with a hot climate, increasing heatwaves, water shortage, substantial poverty and an inadequate health system, only 25 people died of heat stroke in a 100-day heat season.  

Under-reported deaths

2019 has been one of the hottest years on record. Temperatures in parts of India have crossed 500 C. Most parts of Central, North and West India are in a grip of severe heat wave. Several heat stroke deaths have been reported in Telangana, Andhra Pradesh and Maharashtra. Reports from Andhra Pradesh alone suggest that more than 433 people have suffered heat stroke.  

There is published analysis from Ahmedabad which showed that in 2010, when there was a major heat wave in for one week in May, 800 people died of heat stroke. But the number of cases of such deaths reported were only 80.

That’s what we mean by the iceberg of heat wave deaths — only 10% of an iceberg is visible, 90% is not. Just like in the heat wave deaths reported in Ahmedabad in May 2010. The rest are not labelled as heat stroke deaths, although they are. This happens often with the death of older people or the very young and other vulnerable groups. India is not unique in this.

In Chicago’s great heat wave of 1995, 800 died, but only 400 were certified as heat-related deaths. And Chicago has very good health and police systems and a coroner’s office, which capture all deaths and classify the causes.

What is the main lesson on data from Ahmedabad’s heat wave deaths? Our public health systems should look for ‘excess than usual mortality’ during heat waves and not only ‘heat stroke’ labelled deaths.

Each city, town, district and state must total the deaths by all causes that happen on each day during the summer and compare that with the past 10-20 years’ average for that season and that day — just as the weather department does when it says the temperature is above or below normal. This will tell public health authorities if the deaths are within normal range or not.

We also need to co-relate the number of daily deaths with the temperature and humidity for that day and preceding few days to know if mortality is rising during the heat wave period or not.

In Ahmedabad, during the peak heat day of the heat wave of 2010, there were 315 deaths due to all causes as compared to about 100 deaths during a normal summer day that year. This is a 300% rise in daily mortality.

Gross daily mortality

Similar increases in mortality have been observed during heat waves in Nagpur, Bhubaneshwar and Surat. In short, health authorities must look for a rise in gross daily mortality in the cities and districts during the heat wave period rather than reporting only ‘heat stroke deaths’.

The registrar of birth and deaths in cities and districts must monitor daily deaths and provide details to alert authorities and citizens. Health departments, both urban and rural, should monitor daily ambulance calls and hospital admissions as a rough guide for heat wave impact assessment.

When one person dies in a certain geographic area, there are probably 10 to 100 people admitted to hospitals with similar symptoms. So, hospitalisation rate may be a much more accurate indication of heat wave health impact than mortality.

We hope that in this season the Registrar General at the central level and the state registrars of death and directors of health will monitor and report daily hospital admissions and gross mortality to detect rise in these indicators during the prevailing heat wave season.

Heat-related mortality is preventable with timely action, as seen in most parts of Europe as well as in India, where timely action in Ahmedabad, Nagpur and Bhubaneshwar have helped avert fatalities.

Over time, properly implementing heat action plans through building capacity, involving the citizens and initiating simple steps for advocacy, as suggested by NDMA, can help save thousands of lives as well as build resilience at community level.

Advocacy should also include the traditional methods and practices followed by different communities for combating the impacts of heat.

(Mavalankar is Director, Indian Institute of Public Health Gandhinagar (IIPHG); Saunik, IAS, is Takemi Fellow at Harvard University; Golechha is faculty at IIPHG).

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