Climate change and the nervous system: why we need to pay attention

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

Practical actions

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.

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Figure 1

Ideas for discussion of climate change in clinic.

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?

Climate anxiety

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).