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Aletta Jacobs School of Public Health
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Aletta Jacobs School of Public Health
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Heatwaves and chronic diseases: health challenges of the 21st century

Datum:27 augustus 2021
Manuela Fritz
Manuela Fritz

Manuela Fritz, a PhD Candidate at the Department of Economics, Econometrics and Finance (UG), and at the Chair of Development Economics (University of Passau)

Most of you will probably agree with me that climate change will pose the most detrimental threat to decent health in the forthcoming decades. While climate change can affect health in various ways – from accelerating the spread of infectious diseases to causing floods or draughts – the most direct link is the impact of heat on the human body. And we do not even have to wait for decades: already today we see the harmful consequences of heatwaves.

While writing this blog, Western North America experienced unprecedent temperatures up to 50°C in June 2021, leading to a death toll of around 600 individuals in only one week. In its issue from July 3rd, The Economist stated that in 2018 more than 300,000 people over the age of 65 died as a consequence of extreme heat, most of them living in India or China. These numbers are shocking, out of question. Yet, in this blog I want to draw your attention to the health consequences triggered by heat that do not immediately result in fatalities and hence seldom generate headlines in newspapers but make the heat-health nexus even more complex and dangerous.

With my current research, I investigate health effects which – at first glance – cannot be easily linked to extreme temperatures. Specifically, I explore whether primary health care visits that occur at general practitioners or community clinics increase with high temperatures. To do so, I combine meteorological weather data with insurance data from one of the world’s largest health insurance schemes: BPJS in Indonesia. The country has two characteristics that make it especially interesting to focus on in the context of the heat-health nexus. First, it has a tropical climate, meaning that the population has likely adapted to hot temperatures, and hence, if I do find effects for Indonesia, the results might be broadly applicable to other low- and-middle income countries that are majorly located in the Global South. Second, the country’s disease burden structure is quite similar to what we see in high-income countries. The three leading causes of the disease burden in Indonesia are all non-communicable diseases (NCDs): stroke, ischemic heart diseases and diabetes. Such a disease burden structure was for a long time unique to high-income countries, yet it has also become increasingly common in low- and middle-income countries. Focusing on NCDs in particular, hence, allows to predict the health effects of climate change for diseases that account for 70% of the global disease burden worldwide.

The results of my research even came as a surprise to myself. I had expected to find some small increases in the number of health care visits when temperatures increase, yet never had I imagined effects of that size. On days where the average temperature surpassed a threshold of 29.5°C, the number of daily primary health care visits increased by more than 12%. Even more striking was the disproportional increase for people suffering from or being at risk of NCDs; the number of individuals with diabetes or cardiovascular diseases that visited a doctor increased by 30% and 19%, respectively.  

I dug a bit deeper to find out whether this increase was only temporary, i.e. whether such a peak in visits on one day would be followed by less visits in the next days or weeks (an effect often observed for heat-related deaths and labelled as “harvesting”). Again, there were some interesting differences between all visits and NCD-related visits. While the peak was only temporary when I considered all visits and did not differentiate by diagnosis, the increase for NCD visits was permanent and not offset even after a period of four weeks. This implies a substantial permanent burden on the health care system, both financially as well as logistically for doctors and nurses.

Given that the disease burden of NCDs is estimated to increase in low- and middle- income countries in the coming decades – due to population aging, unhealthy lifestyles and urbanization – the health effects of climate change will hit these countries hard. Policymakers should address this problem quickly, perhaps by establishing a system where health care facilities receive early information and warnings of impending heat events from local meteorological services. Furthermore, individual early-warning systems and targeted information to individuals at risk could be helpful and thanks to digital devices, easy to implement.

Most importantly, awareness should be shifted from just acknowledging the death toll resulting from extreme temperatures, to emphasizing the adverse health consequences that do not result in fatalities, especially for pre-existing NCDs. Ignoring the increasing burden at the primary health care level could result in substantially underestimating the health and economic consequences of future heatwaves. Climate change is inevitable, but at least we can correctly estimate its adverse health impact to identify areas that will be most severely affected, so that policymakers can effectively target preventive measures.

About the author:
Manuela's research lies at the intersection of health economics and development economics and focuses on how to improve public health in low-and middle-income countries, in particular in the context of chronic diseases.

Contact: m.k.fritz , manuela.fritz Twitter: @ela_fritz