In October 2021, a group of over 120 leading global experts on climate, public health, economy, and political science among others, voiced growing concern over the impact of climate change on the livelihood of communities around the world, its direct and indirect effect on mental and physical health, and its contribution to the spread of infectious diseases
More recently, the 2022 report by the Intergovernmental Panel on Climate Change (IPCC) notes that extreme weather events caused by human action are surpassing the resilience of some ecological and human systems, sometimes with irreversible effects. The report also emphasizes the impact of climate change on mental and physical health, and the ways in which changes in climate and weather patterns are contributing to the spread of vector-borne communicable diseases.
The latest IPCC report also notes that the world is now 1.5 degrees Celsius warmer than in the pre-industrial period (1850–1900), with the past few years registering record temperatures. Previous studies have also reiterated that climate change, particularly extreme heat and extreme weather events, which are predicted to become the norm in coming years, can have a direct negative impact on the human body in many ways.
Research by scientists at the Karolinska Institute in Sweden now show that more and more people are getting hospitalized with hyponatremia — abnormally low sodium levels — due to high outdoor temperatures. The sodium deficiency associated with hyponatremia generally is usually the result of low intake of salt, high loss of salt, or the excess water in the body. Two plausible explanations given by researchers at Karolinska for heat-related hyponatremia are either salt loss from excessive sweating due to heat, or excessive hydration by drinking more fluids due to a fear of dehydration.
There is also evidence of extreme heat exacerbating neurological disease. One review from August 2021 showed that increasing ambient temperatures was linked to a worsening of symptoms of various neurological conditions, from Alzheimer’s disease and Parkinson’s, to epilepsy and migraine, as well as a higher number of hospitalizations and a higher risk of death related to these conditions.
Other health risks to the body from higher temperatures include that to the digestive system, where exposure to extreme heat have been shown to increase the permeability of digestive barriers, and consequently increase the susceptibility to infections through the digestive system. In addition, there is growing evidence to prove a link between heat exposure and kidney disease, particularly in outdoor workers toiling under above average temperatures.
Higher temperatures have also been shown to impact the body’s immune response to pathogens such as viruses. In a study conducted on mice in 2019, researchers found that mice exposed to high ambient temperatures — of 36 degrees Celsius — had a dampened immune response to the influenza virus. Additionally, changing environmental conditions have been found to increase the transmission of many water-borne, air-borne, food-borne, and vector-borne pathogens, undermining the efforts of medical scientists and public health organizations to mitigate this threat.
Among the diseases whose transmissibility have been shown to increase due to climate change-related factors are malaria, dengue, Zika, and chikungunya, all of which are caused by arboviruses — a group of viruses spread to people by the bite of infected arthropods (insects) such as mosquitoes and ticks.
Climate change also affects the environment where pathogen-carrying vectors — such as insects, particularly mosquitoes — live, enabling them to spread to new regions. This has been shown by the increase in the number of cases of malaria and other transmissible diseases in Europe and farther around the world.
The report by the experts group mentioned earlier found governments and decision-makers lacking in their efforts to stop climate change and mitigate its negative impacts, especially on health. The report also notes that there are several smaller-scale steps that individuals and healthcare organizations can take to pull their weight in terms of becoming more eco-friendly. On the personal level, this includes living healthier lifestyles by reducing the burden of disease through more physical activity, through healthier, more plant-based diets, through reduced exposure to air pollution and other environmental determinants that damage our health.
On an organizational level, health services could set the tone in terms of how we address the climate crisis, and how we understand its effect on public health. If we treat climate change as a health issue, and not just as an environmental issue, this would make it more immediate to everybody.