The One Health Approach was developed by the World Health Organization (WHO) in 2017. The Approach recognizes that people, animals and the environment are interconnected, and we need to better understand these linkages to achieve better public health outcomes. This is all the more important as we become increasingly aware of the health impacts of climate change. The WHO recommends that many professionals with a range of expertise who are active in different sectors, such as public health, the environment, government, and research join forces to support One Health approaches by breaking down silos and fostering collaborations.
The environment and climate change are already impacting our health in ways we can measure. As the climate changes, we are seeing more frequent and intense exposure to extreme heat and its consequences. The 2021 Lancet Countdown Report on Health and Climate Change estimates that 72% of countries saw an increase in human exposure to wildfires and that more than 3 million deaths occur as a result from air pollution each year. The most vulnerable are often the worst affected, and therefore, the health effects of a changing climate are exacerbating already present inequities within and across countries, particularly in lower- and middle-income countries.
We must not forget that the brain is part of the human system. Therefore, understanding the interplay between brain health and the environment as part of a One Health Approach is crucial. Indeed, the brain is impacted by the external environment, including viruses (such as SARS-CoV-2—the virus which causes COVID-19), and other infectious agents that may result in disease processes. For example, in the case of Long COVID (the phenomenon where COVID-19 survivors experience symptoms that persist weeks and months after infection), there are over 200 reported symptoms, including neurological effects such as brain fog.
Climate change impacts brain health in many ways, whether through an increased risk of strokes, migraine or seizures with increased heat exposure, the effects of air pollution on dementia and brain health, or the increased prevalence of infectious diseases which have consequences on the brain. There is also growing interest in how viruses (in general, and zoonotic in particular) may contribute to the development of neurodegenerative diseases, such as Alzheimer's, Parkinson's and Multiple Sclerosis.
To date the intersection of brain health and the physical environment has not been well studied. While different hypotheses have been pursued, including on mental health and the environment, the key scientific questions are still being defined. Climate change, population growth and other demographic shifts make addressing this void an imperative.
Effects on human brain health will become more pronounced with the potential for more infectious outbreaks, including future pandemics, as the climate warms, human built-environments expand, and animal-human interactions increase. What happens outside the brain impacts brain health. Understanding brain health, also means understanding that the environment and health intersect.
Paradigm-changing science is happening at points of intersection, where diverse fields and disciplines are joined in new ways to deliver new insights. This pandemic has reinforced both our interconnectedness with other humans, and our connection to the environment. Solutions to the health consequences will therefore lie in a greater exploration of these points of connection.