‘We are called to be architects of the future, not its victims’—Buckminster Fuller
People with chronic neurological conditions may be vulnerable to change and less able to manage its demands: neurological diseases are among the most burdensome. Whether climate change has particular effects on specific neurological diseases or not, the known impaired resilience to change affecting people with neurological diseases requires neurologists to have awareness of potential climate impacts and their management. Preparedness should include understanding of general national and local alerts and action systems, and the ability to advise patients about managing extreme weather events, particularly heatwaves, but also floods and cold snaps. At the same time, we need more research into the particular consequences of climate change on specific neurological diseases. Climate change is a serious healthcare issue, requiring the neurological community to respond as it would, or did, to other serious challenges, such as COVID-19. As disease experts, we all have a role to play.
- CLINICAL NEUROLOGY
- HEALTH POLICY & PRACTICE
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Climate change: an existential threat here now
Human impacts on the ecology and geology of the entire planet are now so great that they are measurable and have led to the declaration of a new geological epoch—the Anthropocene, with climate change a key component. Our climate is changing around us, now. Early July 2023 was marked by the three highest world average surface temperatures since records began, of 17.01°C, 17.18°C and 17.23°C.1 The atmospheric CO2 level is at its highest for nearly a million years, and more than 50% higher than preindustrial times: in May 2023, CO2 peaked at 424.0 parts per million (ppm).
We are not used to these metrics: they are difficult to grasp. Consider an analogy. Normal blood pH is around 7.4, equating to a blood hydrogen ion concentration of ~4×10–8 molar. Doubling the blood hydrogen ion concentration, conceptually as fundamental a change as that happening to our world currently, would lead to a blood pH of around 7.1, with complicated clinical consequences including drowsiness, stupor, coma and death. Which of us would watch a patient’s pH falling in front of our eyes to this level and not act, not admit them to ITU, and not get all our colleagues involved to do something? What are we doing about an effect of equivalent magnitude, complexity and threat to life itself?
For a more formal perspective, the Royal Society has provided an excellent digestible summary of the complexity of climate change.2 The Earth’s climate is warmed by absorbing solar energy, which hits the Earth, and is radiated back into the atmosphere at longer wavelengths. ‘Greenhouse gases’ in the atmosphere itself absorb this energy and radiate it in all directions, including back down to the Earth: this effect has enabled the development and survival of life on our planet. Greenhouse gases include water vapour, carbon dioxide, methane and nitrous oxide (and now also anthropogenic anaesthetic gases, which are potent greenhouse gases) keeping the surface and lower atmosphere warm. Increasing the concentration of greenhouse gases amplifies the greenhouse effect—making the planet warmer. Carbon dioxide concentrations are now higher than at any time over the last 800 000 years: the elevation, most marked over the last 50 years, is due to human activity, mainly the burning of fossil fuels. The Earth’s global average surface air temperature has risen by >1°C since 1900. The Earth’s surface area is 5.1×1014 m2—so while a number like 1°C may not sound like much, it represents an enormous amount of additional heat in the system. This extra heat has profound and complex consequences in a planetary system that has not exceeded relatively narrow bounds for time over an evolutionary scale. Global concern about climate change led to the Paris Agreement,3 which established a global framework to avoid dangerous climate change by limiting global warming to less than 2°C and intending to keep it within 1.5°C. The agreement has been ratified by every country except Iran, Libya and Yemen, and aims to bolster national abilities to deal with the consequences of climate change. The Conference of the Parties (COP) is the main decision-making body of the United Nations Framework Convention on Climate Change (UNFCCC), encompassing all countries that are Parties to the UNFCCC; COP assesses how well measures taken to limit climate change by the Parties match up to the overall goal of the UNFCCC, and is a venue where decisions are made. We are not doing well in this evaluation. Even if every new pledge made at the Glasgow COP26 climate negotiations in 2022 were met, the average global surface air temperature would rise 2.4°C–2.7°C by 21004, exposing more than 3 billion people to mean average temperatures >29°C, with extreme heat events, like heatwaves, affecting far more.
High temperatures and heatwaves affect health. For example, recent European heatwaves were associated with thousands of excess deaths, the causes of which included heatstroke and aggravation of existing conditions. Deaths directly due to adverse weather events are likely to be underestimated.5
Climate change and the nervous system: why we need to pay attention
Thermoregulation is a neural process
Under normal circumstances, humans maintain their body temperature within a narrow range that is optimal for protein integrity and function. One line of thinking suggests that evolution from early mammals to modern humans required, among many other steps, brain-led coordination of mechanisms permitting endothermic homeothermal life, balancing heat generation and heat loss, and producing a warm environment in which levels of neuronal activity did not depend on the external temperature, in turn generating advantages over ectothermal lifeforms (eg, reptiles) and allowing occupation of different niches, such as hunting in non-forest environments. Running after prey required many adaptations. Whatever its origin, thermoregulation is a neurally driven process6 and is complicated.7 8 Temperature-sensitive neurones are everywhere in the body (including the brain). The limbic system and anterior hypothalamus receive sensory inputs from these detectors via the spinal cord. There follows neural coordination of behavioural and autonomic physiological systems that activate warming (eg, through shivering) or cooling (through cutaneous vasodilation and sweat production) as needed; local (skin) reflexes also operate. Other inputs that influence activity of temperature-sensitive systems include interleukin-1 and prostaglandin E, glucose and ion concentrations, osmolality and sex hormones. Response systems need muscle engagement, vasoactivity and sweating. When temperature regulation fails, for example in heatstroke, other neural structures, such as the cerebral cortex, thalamus, basal ganglia and cerebellum,9 10 are also involved through multifactorial pathophysiology, sometimes constituting a posterior reversible encephalopathy syndrome.10
Disordered thermoregulation in neurological disease
Because neural structures are central to thermoregulation, it is unsurprising that neurological diseases may compromise thermoregulation—and therefore undermine the ability to cope with rising temperatures and, especially, heatwaves. Disordered thermoregulation has been shown in several neurological diseases, including multiple sclerosis, synucleinopathies, Alzheimer’s disease, spinal cord and autonomic dysfunction and peripheral neuropathies of a wide range of causes,6 and is suspected to affect people with several rare neurogenetic conditions, such as Dravet syndrome,11 Phelan-McDermid syndrome12 and many others. High ambient temperatures have been shown to aggravate symptoms in dementia, Parkinson’s disease, multiple sclerosis, migraine and some epilepsies. Many medications directly or indirectly compromise thermoregulatory capacity,13–15 for example, antipsychotic and anticholinergic agents, some antiseizure medications16 17 and diuretics.18 If thermoregulation is disordered, the function of temperature-sensitive components of the nervous system may, in turn, be disrupted. For example, ion channels, central to neuronal activity, demonstrate exquisite sensitivity to ambient temperature,19 and this effect also extends to channels mutated due to disease-causing genetic variants.20
Vulnerability to adverse weather and climate change
Coping with temperature extremes, both high (which will become the greater challenge with global warming) and low, requires specific responses by humans. Responses may include donning or doffing clothing, moving to warmer or cooler environments, activation of external temperature-regulating systems, as well as autonomous measures, such as cutaneous vasodilation, evaporative cooling through sweat production or shivering and non-shivering thermogenesis.6 Environmental humidity multiplies the physiological stress of higher temperature, disrupting evaporative heat loss. Any of these processes might be compromised in neurological disease, quite separately from the presence or absence of compromised thermoregulation. For example, people with cognitive impairment, of any cause, may not take necessary behavioural actions, or may not be able to articulate their need to do so. Heat-induced weakness in multiple sclerosis may prevent movement to a cooler environment. Some people tolerate temperature extremes better for various reasons,21 with evidence that physical fitness improves acclimation capacity.6 The built environment can amplify the impact of heatwaves, effects of which may last longer indoors than they do outdoors. Straitened economic circumstances due to loss of earnings related to neurological (and other illnesses) may reduce the ability to take countermeasures to climate challenges. Supply chains for essential medications, and healthcare services themselves, may be compromised by extreme temperatures, or climate change-related floods.
Climate change and the neurology community: what we can do
The broader picture
Climate change is a current and growing threat to health.22 Its pervasive consequences require us to prepare for both imminent acute challenges, which in the UK are mainly heatwaves, cold spells and floods, as well as longer term shifts in weather patterns and other extreme weather events. In addition to prominent calls for more attention and more action with regard to the health effects of climate change, for example, from the Lancet Countdown,23 many governments have already developed, and continue to evolve, plans for health responses to climate change. In the UK, the Greener National Health Service (NHS) programme is an example of longer-term planning to reduce the contributions of healthcare itself to climate change.24
Plans are in place for acute challenges we have already faced and will continue to experience with increasing frequency and severity. There is an Adverse Weather and Health Plan (AWHP),25 under the responsibility of the UK Health Security Agency (UKHSA), as part the National Adaptation Programme.26
Whether or not it turns out that climate change carries specific risks for people who already have neurological diseases,27 or increases the risk of people acquiring neurological diseases, climate change will in any case have effects on the entire population, and especially on vulnerable groups such as the very young, the very old, and those with pre-existing medical conditions. It is therefore incumbent on us to think about climate change effects on people with neurological diseases, who may already carry significant health burdens. Our actions can follow generic guidance28 but can also be tailored to individuals and diseases based on our shared expertise in those diseases, with examples from other disease areas already dealing with heatwaves.29 As clinicians, we can read the room and provide information with sensitivity to the individual context.30 Moreover, healthcare professionals are consistently rated as among the most trusted workers: we can contribute to actions against climate change at every level, from making climate change a component of the conversation with people with neurological diseases as part of duty of care, to extending that obligation to other forums for population and public health. Such action need not be political: promoting awareness, research and action around climate change is legitimately as much part of our daily work as advising patients about the adverse consequences of smoking, obesity and substance abuse. We already do this, typically through raising awareness, promoting actions and, especially, empowerment: we all know lecturing rarely works to achieve meaningful behaviour change. Such efforts are about health, health improvement and preventing health decline and aggravation of inequity due to the additional, predictable and enormous challenge from climate change. Promoting a healthier environment, and health equity, has long been a valid medical pursuit. As more research is undertaken into the effects on neurological diseases of climate change, we can make discussions at every level more specific and targeted, while retaining a broader advocacy role. Healthcare systems are themselves prominent generators of greenhouse gases. While some national systems have declared their intent to become net zero emitters of greenhouse gases, emissions from others continue to rise. But healthcare systems are powerful and innovative: they can take a lead and learn from others at every level, for example, we can advocate for better environments and nutrition in hospital—for patients and staff; we can lobby for greener transport for all (5% of all road traffic in the UK is linked to the NHS); we can retain and improve telemedicine, learning from the pandemic, including maintaining practice that had had to become adapted to remote assessment at that time.31
The UK Climate Change Act 2008 mandates responsibilities for actions to adapt to climate change. The AWHP,25 though probably not familiar to most of us, is a rich resource not only describing the multiagency plans for response to climate change, in particular for heat, cold and flooding, but also providing links to useful documents. Its goals, such as preventing increase in years of life lost due to adverse weather events, preventing associated mortality and morbidity, are stark declarations of the present dangers of climate change. Its objectives include improvement of preparedness, resilience and response to adverse weather events. The AWHP is the responsibility of the UKHSA Extreme Events and Health Protection team, within the UKHSA Centre for Climate and Health Security, and is intended not only to be relevant currently, but also for the long term. The related guidance describes actions needed before and during adverse weather events, for which there is a requirement for national and local organisations, including NHS bodies, to have contemporary delivery plans. Notably, section 5.4.2 states ‘All health and social care staff should be prepared for extreme heat and cold weather events and understand their impacts on health. They should understand the actions that need to be taken individually and organisationally to ensure the safety and health of their clients and patients during such events and the preparations that need to be taken in advance. There is an ongoing need to ensure that all staff working with patients and clients are trained both to understand the impact of extreme heat and cold on bodily functions and to be alert to the physical and mental signs of impact on health. All staff should be made aware of the new weather and health alerting service and the good practice actions which follow on from these (introduced from summer 2023)’.25 The CQC also considers adverse weather, and related planning and preparedness in its constituency, under regulations 12, 15 and 17. Related to the AWHP, a host of resources are available (table 1).
Tables 2 and 3 offer some practical steps. Many people with neurological diseases already have specific advice provided in case of particular circumstances, for example, rescue protocols providing advice on the emergency or supplemental use of benzodiazepines for people with epilepsy: such protocols should be adapted to include advice on management during adverse weather events, ideally with relevance to the predicted severity and patient’s location. As disease experts, it falls to us to provide such information based on our understanding of the patient’s condition and the best currently available evidence for potential, or observed, effects of climate change (as we did for COVID-19). Be ready to speak with patients about climate change (see figure 1). Consider giving advice on storage of medications32–34 (see tables 2 and 3), as well as organisational preparedness for supply chain disruptions.
Advice should be explicitly linked to early warning systems for health and weather. In the UK, the heat-health alert system operates from 1 June to 30 September, and the cold-health alert system from 1 November to 30 March, with additional weather warnings through the National Severe Weather Warning Service. In addition, the UKHSA may issue a National Patient Safety Alert or Urgent Public Health Message for particular, severe weather events. The Heat-Health Alerts platform has a colour-coded rating system.35 The UKHSA also provides heat-related mortality reports.36
Despite all these structures and policies, evidence-based information and advice specifically for people with neurological conditions remains sparse. Other than for stroke and neurological infections, particularly West Nile virus, there has been remarkably little published research. Existing data can be conflicting, and interpretation requires care and appreciation that the pace of climate change has been such that older papers may have been measuring outcomes related to climate circumstances that we have already surpassed. Even the magnitude of global and local temperature changes observed over the last 40–50 years, and the increasing frequency and severity of extreme weather events, may be relevant: preliminary data suggest that in vitro exposure of human brain cells to changes in ambient temperatures of just 2°C can alter the expression of 10% of the genome, while intraventricular CSF temperature may change by that amount (2°C) with ambient indoor seasonal temperature changes. This should push us to listen to, and enquire about, our patients’ concerns and experiences—there may not be the evidence base that we consider necessary to ‘underpin’ belief in such reports, but that does not invalidate such observations, which are already being made by, and raising concern among, members of disease-specific charities. Surveys that we have undertaken show that people with neurological conditions, their carers, neurological healthcare professionals and scientists are as concerned about climate change as the general population. Patient groups may already be taking their own action,11 including providing members funding for air conditioning—a potentially life-saving, acute, expedient measure, but one that is not a sustainable global long-term solution.
We need to imagine the shape of net zero neurology, as part of the overall NHS commitment to net zero. We can make a difference: desflurane is an enormously potent greenhouse gas anaesthetic agent—the work of the anaesthetic community has led to its planned removal from NHS practice,37 the first drug to be decommissioned for the sake of the climate. There are likely to be many opportunities to undertake research to better inform practice: perhaps not all neurological conditions, or their subtypes, will experience detrimental effects from climate change and better understanding disease-specific impacts should permit better targeting of limited resources. We can make a difference in our own spheres of influence: we are all likely to have to change something for the NHS net-zero target to be met, and why not do so in ways that produce co-benefits? For example, could we shift clinics during heatwaves from unbearably hot rooms to the evening, making the all-round effort needed, with health co-benefits for patients and staff?
Thinking seriously about climate change can itself cause anxiety, in patients, healthcare professionals—and even climate scientists. Climate anxiety is common, especially among the young.38 Some have described the process as part of an individual climate journey. We should think how the next generations of neurologists will be able to practise and do so in a liveable world. There are ways to reduce climate anxiety (table 4).
We are changing the Earth at rates and magnitudes beyond which most life can easily adapt. These changes are so big that they may feel beyond comprehension—or beyond our willingness to accept what is happening. But inaction is not an option. We have a duty of care to our patients and to our colleagues. Mitigating climate change has to be a governmental responsibility—but as healthcare professionals, we all have a powerful voice worth using. We have to educate ourselves, and advocate for our patients, at all levels. We have to learn how to talk about climate change—at all levels—but we are used to dealing with complicated issues and sharing information in sensitive, nuanced and appropriately weighted dialogue. It is up to us to act in our own professional arena. To lead the lives we want to lead, we have to change the lives we are leading.
Climate change is happening and will have detrimental impacts on incidence and symptoms of neurological diseases, and mortality from many such conditions.
National systems and local processes, including National Health Service action plans, are in place to provide alerts and support in the event of adverse weather events.
Providing information, advice and comprehensive management plans for adverse weather events is part of the duty of care for all healthcare professionals, including neurologists.
Neurologists should use their powerful voice for advocacy for patients against climate change because climate change will affect the health of most people with neurological diseases.
Maslin MA. How to save our planet. Penguin Life. Published: 2021. ISBN: 9780241472521
Data availability statement
No data are available. No data were produced for this article.
Patient consent for publication
I thank Dr Sara Leddy, Climate Neurology Fellow supported by the National Brain Appeal and the Epilepsy Society and Dr Angeliki Vakrinou, Research Fellow supported by the Epilepsy Society, for comments on the manuscript, and inspiring colleagues across the world working to raise awareness, promote research and take action against climate change.
Collaborators Not applicable.
Contributors SMS wrote the article.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Commissioned; externally peer reviewed by David Nicholl, Birmingham, UK.