The climate changeand its effects on weather patterns and adverse weather events, could adversely affect the health of people with brain conditions, a UCL-led team of researchers claims.
The study was published on The Lancet Neurology.
The repercussions of climate change on brain health
The team highlights the urgent need to understand the impact of climate change on people with neurological conditions, in order to preserve their health and prevent worsening inequalities.
Following a review of 332 papers published worldwide between 1968 and 2023, the researchers, led by Professor Sanjay Sisodiya (UCL Queen Square Institute of Neurology), said they expected the scale of the potential effects of climate change on neurological diseases will be substantial. .
They looked at 19 different nervous system conditions, chosen based on the Global Burden of Disease 2016 study, including stroke, migraine, Alzheimer’s disease, meningitis, epilepsy and multiple sclerosis.
The team also analyzed the impact of climate change on several serious but common psychiatric disorders, including anxiety, depression and schizophrenia.
Professor Sisodiya, who is also director of the genomics department at the Epilepsy Society and a founding member of Epilepsy Climate Change, said: “There is clear evidence of an impact of climate on some brain conditions, particularly strokes and nervous system infections.
Climate variations shown to have an effect on brain diseases included extreme temperatures (both low and high) and greater variations in temperature over the course of the day, especially when these measures were seasonally unusual.
“Nighttime temperatures may be particularly important, as higher temperatures during the night can disrupt sleep. Poor sleep is known to aggravate a number of brain conditions.”
Researchers found that there was an increase in hospitalizations, disability or mortality following a stroke in higher ambient temperatures or heat waves due to climate change
Meanwhile, the team says that people with dementia are susceptible to harm from extreme temperatures (for example, heat-related illnesses or hypothermia) and weather events (for example, floods or fires), as cognitive impairment can limit their ability to adapt behavior to the environment.
The researchers write: “Reduced risk awareness combines with a reduced ability to seek help or mitigate potential harm, for example by drinking more in hot weather or adjusting clothing. This susceptibility is exacerbated by frailty, multimorbidity, and psychotropic medications. As a result, greater temperature variation, hotter days and heat waves lead to increased hospitalizations and mortality associated with dementia.”
Furthermore, the incidence, hospitalizations, and mortality risk for many mental health disorders are associated with increased climate change, daily temperature fluctuations, or extremes of heat and cold.
The researchers note that as the severity of adverse climate change increases and global temperatures rise, populations are exposed to worsening environmental factors that may not have been severe enough to affect brain conditions in some of the previous studies reviewed as part of the analysis.
As a result, they say it is important to ensure that research is up to date and considers not only the current state of climate change but also the future.
Professor Sisodiya said: “This work takes place against a backdrop of worrying worsening climate change and will need to remain agile and dynamic if it is to generate useful information for both individuals and organisations. Furthermore, there are few studies estimating the health consequences of brain disease under future climate scenarios, making advance planning difficult.”
He added: “The whole concept of climate anxiety represents an additional, potentially burdensome influence: many brain conditions are associated with a higher risk of psychiatric disorders, including anxiety, and such multimorbidities may further complicate the impacts of climate change and the adaptations necessary to preserve health. But there are actions we can and must take now.”
Are climate change and air pollution worsening neurological diseases?
People with neurological diseases such as headaches, dementia, multiple sclerosis (MS) and Parkinson’s disease may experience worsening symptoms due to climate change, according to an in-depth review of research published in the November 16, 2022 online issue of Neurology. The review also found that stroke could become more prevalent due to climate change.
“Although the international community seeks to reduce global temperature rise to below 2.7°F before 2100, irreversible environmental changes have already occurred, and as the planet warms, these changes will continue to occur.” , said review author Andrew Dhawan, MD, DPhil, of Cleveland. Clinic in Ohio and member of the American Academy of Neurology. “As we witness the effects of global warming on human health, it is imperative that neurologists anticipate how neurological diseases might change.”
For the review, the researchers examined published studies on climate change, pollutants, extreme temperatures and neurological diseases between 1990 and 2022. They identified 364 relevant studies in three categories, including 289 studies on the impact of pollution, 38 studies on extreme weather events and temperature fluctuations and 37 studies on emerging neuroinfectious diseases. They only included studies on adults, not children.
Studies have highlighted relationships between temperature variability and worsening neurological symptoms, warming climates and tick- and mosquito-borne infections, as well as air pollutants and the rate and severity of cerebrovascular disease.
The review showed that extreme weather events and temperature fluctuations were associated with the incidence and severity of stroke, migraines, hospitalization of dementia patients and worsening of MS.
It showed that for emerging neuroinfectious diseases such as West Nile virus, meningococcal meningitis, and tick-borne encephalitis, climate change has expanded favorable conditions beyond traditional geographic areas and that these animal- and insect-borne diseases lead to disease risk in new populations.
The review also showed that exposure to air pollutants, particularly nitrates and fine particulate matter, also known as PM 2.5, polluting particles smaller than 2.5 microns in diameter, was associated with incidence and severity of stroke, headache head, risk of dementia, Parkinson’s disease and worsening of MS.
“Climate change poses many challenges to humanity, some of which are not well studied,” Dhawan said. “For example, our review found no articles related to neurological health effects from food and water insecurity, but these are clearly linked to neurological health and climate change. Further studies are needed on ways to reduce the transmission of neuroinfectious diseases, how air pollution affects the nervous system, and how to improve the delivery of neurological care in the face of climate-related disruptions.”
One limitation is that the studies were conducted in resource-rich regions of the world, suggesting that the findings may not be applicable in regions with fewer resources where such changes may be even more likely.
More than half a million stroke deaths worldwide could be linked to climate change
According to a study published in the April 10, 2024 online issue of Neurology, climate change may be linked to increased mortality and disability due to stroke in regions around the world.
Researchers found over three decades that suboptimal temperatures—those above or below temperatures associated with the lowest mortality rates—were increasingly linked to death and disability from stroke. The study does not prove that climate change causes stroke. Shows only one association. The study also did not look at other risk factors such as high blood pressure and high cholesterol levels.
The researchers found that the majority of these strokes were due to lower-than-optimal temperatures, however they also found an increase in strokes linked to higher-than-optimal temperatures. In colder temperatures, a person’s blood vessels may narrow, increasing blood pressure.
High blood pressure is a risk factor for stroke. Higher temperatures can cause dehydration, affecting cholesterol levels and slowing blood flow, which can also lead to a stroke.
Dramatic temperature changes in recent years have affected human health and caused widespread concern,” said study author Quan Cheng, Ph.D., of Xiangya Central South University Hospital in Changsha, China. “Our study found that these temperature changes may increase the burden of stroke worldwide, especially in older populations and areas with greater health disparities.”
For the study, researchers examined 30 years of medical records for more than 200 countries and territories. They looked at the number of stroke deaths and the burden of stroke-related disability due to suboptimal temperatures.
They then split the data to look at different regions, countries and territories. They also looked at age groups and genders.
In 2019, there were 521,031 stroke deaths related to suboptimal temperatures. There were also 9.4 million disability-adjusted life years due to strokes linked to suboptimal temperatures. Disability-adjusted life years are the number of years of life lost due to premature death and years lived with illness.
Comparing low temperatures to high temperatures, they found that 474,002 of the total deaths were linked to low temperatures.
The researchers found that the rate of death from stroke due to temperature changes for male participants was 7.7 per 100,000 compared to 5.9 per 100,000 for female participants.
Looking at regions, Central Asia had the highest death rate from stroke related to suboptimal temperatures at 18 per 100,000. Nationwide, North Macedonia had the highest death rate at 33 per 100,000.
“Further research is needed to determine the impact of climate change on stroke and identify solutions to address health inequities,” Cheng said. “Future research should aim to reduce this threat by finding effective health policies that address potential causes of climate change, such as fossil fuel burning, deforestation and industrial processes.”
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