According to a joint editorial published by over 200 medical journals earlier this year, climate change is the greatest threat to global public health.
Major public health organizations, such as the World Health Organization (WHO), have also voiced similar concerns.
Climate change includes surging temperatures, rising sea levels, and an increase in the strength and frequency of extreme weather events such as flooding, droughts, hurricanes, and wildfires.
Climate change can affect human health in a multitude of ways. Rising temperatures, food scarcity, air pollution, and an increase in infectious diseases are a few ways it can impact human health.
The health effects of climate change are complex and only partially understood, and a more comprehensive understanding is important to help medical professionals provide the necessary care.
A recent systematic review aimed to delineate the impact of global warming on neurological disorders. The study analyzed previous research examining the effects of ambient temperature rises on the occurrence, clinical manifestations, and mortality due to major neurological disorders.
Climate change may render certain parts of the world uninhabitable due to drought, rising temperatures, and other extreme weather events. This will result in the mass displacement of populations, leading to environmental refugees.
The study also analyzed research assessing the occurrence of neurological disorders in migrant populations to understand the potential impact on the brain health of climate-related refugees.
The study found that a rise in ambient temperature due to global warming may lead to worsened symptoms of neurological disorders and result in higher hospitalization and mortality rates.
The effects of migration on the occurrence of neurological disorders were more variable and were also influenced by social, cultural, and economic factors.
However, the authors cautioned that these results were preliminary, and the analyzed studies did not specifically aim to evaluate the impact of climate change on neurological disorders and clinical practice.
The study’s lead author, Daniel Kondziella, a professor at the University of Copenhagen in Denmark, told Medical News Today:
“[This study shows that] there are very good reasons to expect a tremendous negative impact on global brain health within the near future owing to climate change. […] At the same time, there appears to be a fundamental lack of awareness of this problem within the neurological community, as evidenced by the complete absence of appropriately designed research to investigate this problem.”
High ambient temperature
To understand the effects of global warming on brain disorders, the team behind the present study reviewed previous research examining the impact of ambient temperature increases on the manifestation of symptoms of major neurological disorders.
The researchers also analyzed studies assessing the association between ambient temperature and hospitalization and mortality rates due to these neurological disorders.
The neurological disorders that the team examined included Alzheimer’s disease, other forms of dementia, multiple sclerosis, Parkinson’s disease, migraine, epilepsy, and stroke. The researchers also looked at tick-borne encephalitis as an example of an infectious disease involving the nervous system.
The researchers reviewed 84 studies and found that higher ambient temperatures were associated with worse outcomes for individuals with neurological disorders.
For instance, multiple studies found that elevated ambient temperatures were associated with more adverse symptoms, such as irritability, anxiety, depression, and agitation, in individuals with Alzheimer’s disease and non-Alzheimer’s dementia.
Similarly, an increase in ambient temperatures was associated with a decline in cognitive performance and motor function in individuals with multiple sclerosis.
Elevated temperatures also increased the risk of hospitalization and mortality in individuals with dementia and stroke.
The researchers also found a higher incidence of tick-borne encephalitis with an increase in annual temperatures. They identified a few studies suggesting a negative impact of higher temperatures on individuals with Parkinson’s disease, epilepsy, and migraine, but the evidence was limited.
Effects of migration
The team then analyzed studies investigating the occurrence of neurological disorders in migrants.
After analyzing nine studies, the researchers found that the direction of the effect of migration on the occurrence of neurological disorders was variable.
Whether migration increased or decreased, the incidence of neurological disorders among migrants was influenced by cultural, economic, and social factors in their origin and destination countries.
Additionally, the access to healthcare services in both the countries of origin and arrival influenced results.
For instance, the prevalence of stroke was higher in individuals native to and residing in China than those who had immigrated to Western countries. These results were probably due to greater access to healthcare in Western countries and cultural factors, such as higher salt intake, in China.
In contrast, one of the analyzed studies showed that individuals who had emigrated from the Caribbean to London, United Kingdom, had a higher incidence of stroke. Individuals of African descent from the Caribbean have a genetic predisposition for cardiovascular diseases.
It is likely that the interaction of genetic risk for cardiovascular diseases with socioeconomic factors upon immigration may increase the likelihood of stroke in these individuals.
The researchers noted that the studies examining the impact of elevated temperatures on these neurological disorders showed considerable variation in their methodology and study design.
Moreover, none of the reviewed studies aimed to specifically address the impact of global warming and climate-related migration on neurological disorders.
They also noted that most of the analyzed studies that scientists conducted were in wealthier nations. The effects of climate change are likely to be disproportionately experienced by lower-income nations and disadvantaged communities, and, therefore, the results may not be representative.
The researchers also acknowledged that their study only considered the potential impact of global warming and migration on neurological disorders.
Climate change encompasses rising sea levels, drought, air pollution, and loss of biodiversity that may also influence the occurrence and symptoms of neurological disorders.
MNT also spoke with Dr. George Perry, a professor at the University of Texas at San Antonio. Dr. Perry, who was not involved with the study, suggested that other factors, including stress, besides a change in ambient temperature, may be more important in mediating the adverse effects of climate change.
Dr. Perry said:
“The known issue is that global warming is increasing stress and uncertainty, [which] potentiate conditions like Alzheimer’s disease. In the context of increasing environmental degradation — particulate air pollution, resource competition, and conflict — climate change is but one of many stressors where we must reduce or modify the impact to preserve global health for us and the planet.”