UBC EnviroMed

1: Cardiovascular Disease

To contextualize the unequivocal connection between cardiovascular disease and climate change, it is helpful to consider the Global Burden of Disease (GBD) Study – a collaboration of more than 3600 researchers from 145 countries. This 2019 study is the largest global observational epidemiological study that has been published and provides extensive data on different health trends, diseases, and risk factors. (1) This study estimates that air pollution was responsible for approximately 9 million deaths worldwide in 2019, over half of which (61.9%) were attributable to cardiovascular disease.

A review article published in Nature Reviews Cardiology in 2022 is one of the many recent studies to illustrate the connection between air pollution and conditions such as heart failure, myocardial infarction, stroke and cardiac arrythmias. (2)

The Intergovernmental panel on Climate Change (IPCC) defines climate vulnerability as the propensity or predisposition to be adversely affected by climate variability and change. (3) With respect to cardiovascular disease, the elderly population are most vulnerable to temperature-related cardiovascular mortality. (4)

In low-income countries, where in-door air pollution is greater due to the burning of fuel from sources such as wood, coal, dung and charcoal, the health threats are particularly increased in women and children. (5) Further vulnerable sub-populations include refugees and immigrants as sub-optimal housing conditions and socioeconomic inequities in addition to language barriers have all been associated with an increased risk of cardiovascular disease.

Pathophysiology of Air-pollution Mediated Cardiovascular Morbidity and Mortality

Multiple explanations have been put forward in attempts to elucidate the pathophysiology underlying the impacts of climate change on cardiovascular morbidity and mortality.

In a recent review article in the New England Journal of Medicine, the ways by which air pollution cause cardiovascular effects are defined as (A) Initiator Mechanisms which lead to (B) Effector Mechanisms and finally (C) Risk Factor Development. (6)

Effector mechanisms are further discussed in a review published in the Journal of American of Cardiology. The authors describe endothelial barrier disruption, inflammation, prothrombotic pathways and autonomic dysfunction resulting in elevated sympathetic tone in the upper airways. Further effector mechanism impacts include central nervous system mediated alterations in the hypothalamic-pituitary adrenal axis and epigenomic changes. (7).

What do we know about the pathophysiology of Noise Pollution & Cardiovascular Disease?

Noise pollution secondary to excess road traffic may also play a role in exacerbating cardiovascular risk factors and contributing to the burden of cardiovascular disease. In a review published by the European Society of Cardiology in 2022, the pathophysiological underpinnings of the links between CVD and noise are discussed. Excessive noise pollution leading to cortical and sympathetic activation leads to the production of stress hormones such as cortisol. Downstream activation of the renin-angiotensin-aldosterone system subsequently contributes to the development of cardiovascular disease risk factors such as hyperglycemia, hypertension and may favor a pro-thrombotic state. These effects may lead to the development of myocardial infarction, heart failure, stroke and arrhythmia. (8)

Action Strategy 1: Inquire about pollution exposures for each patient when relevant.

“The first step in preventing pollution-related cardiovascular disease is to overcome neglect of pollution in disease prevention programs, medical education, and clinical practice and acknowledge that pollution is a major, potentially preventable risk factor for cardiovascular disease.”

Action Strategy 2: Expand current concepts of classically defined cardiovascular risk factors.

For example, consider how a patient’s exposure to air pollution, noise pollution or vulnerability to extreme weather fluctuations may impact health.

“As health care professionals we have to take care that environmental researchers are getting integrated into guideline writing teams to ensure that in the very near future environmental stressors (e.g. climate change, air pollution), rather than classical risk factors (e.g. high cholesterol or diabetes) are defined as the cardiovascular risk factors of the future.” (9)

Impacts of Climate Change on Cardiovascular Risk Factors:

Type 2 Diabetes

o   Temperature extremes have been associated with elevated fasting plasma glucose levels, insulin resistance and increased incidence and prevalence of diabetes. (10,11).

o   Air pollution has also been strongly associated with insulin resistance and type 2 diabetes. Statistically significant associations between PM2.5 and NO2 have been demonstrated multiple meta-analyses. (12,13).

Reduced Physical Activity

o   Higher temperatures tend to be associated with reduced time spent exercising, further amplifying the risk of cardiovascular disease and associated conditions such as Diabetes and Hypertension. (14)

Hypertension

o   Interestingly, air pollution and temperature extremes appear to have differing impacts on blood pressure. In a 2018 review published in the Journal of the American College of Cardiology, the authors review meta-analyses published on the topic of air pollution and hypertension and emphasize that long-term exposures pollution has been linked to chronic elevation in blood pressure. (15) With respect to temperature, evidence from meta-analysis of 23 studies suggests that there is an inverse relationship between temperature and blood pressure, and that individuals with a pre-existing history of cardiovascular disease, are more susceptible to these effects. (16) The pathophysiology between this relationship is incompletely understood. A sympathetic drive of increased heart rate and thus blood pressure may be galvanized by a decrease in temperature. (17, 18). Conversely, elevated temperatures promote peripheral vasodilation and a decrease in blood pressure. Furthermore, heamatoconcentration and the release of pro-inflammatory cytokines may promote a hypercoagulable milieu and thus increase the risk of thrombosis and stroke. (19)

Lessons Learned from the COVID-19 Pandemic

In a study published in the Lancet Planetary Health, the implications of lock-down measures on diseases related to air pollution (stroke, ischemic heart disease, chronic obstructive lung disease, lung cancer) in China and Europe was explored. This study was predicated on data demonstrating decreased mortality burden from diseases related to poor air quality in the lead up to the 2008 Olympics in Beijing, during which time activity at many industrial plants and construction sites was put on hold leading up to the Games. (20) During the period of February to the end of March in 2020, an estimated 24 200 premature deaths were averted in China as a result in nation-wide reduction in particulate matter concentrations. (21) Of note, the number of fatalities secondary to Covid-18 during this time was 3309. Many of these deaths occurred in the Hubei province surrounding the region’s capital of Wuhan, while the benefits of adverted pre-mature deaths related to improved air quality were widespread across the country. A further 76 400 to 287 00 averted long-term premature deaths in China were hypothesized based on the statistical modelling study adopted.

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2: Mental Health

Mental health conditions are a significant cause of morbidity worldwide. The WHO reports that depression is a leading cause of disability globally. (1) Yet, in many contexts worldwide, stigma against mental health challenges prevails, and effective treatment coverage remains low. (2)

It is against this backdrop of unmet mental health needs that climate change and environmental degradation are taking place. Climate change may impact mental health directly through the trauma of disasters caused by extreme weather events; and through feelings of anxiety, frustration, and powerlessness provoked by an understanding of the trajectory that climate change is currently on. It may also have indirect consequences for mental health – for example, through the losses of livelihoods, food and water insecurity, and violence that will be the likely result of environmental degradation. (3)

It is important to note that the burden of mental health impacts created by climate change will not be distributed equitably. (3) Women and LGBTQ2SAI+ people, young people, and people with low socioeconomic status may be exceptionally vulnerable to anxiety and mood disorders related to environmental change (WHO 2014, in 4).

Ask yourself: How does climate change and environmental degradation impact mental health?

Disaster and Displacement

Climate change is expected to increase the frequency and severity of extreme weather events, such as wildfires, heat waves, floods, and tropical storms. (5) These extreme weather events have the potential to create significant human disasters, particularly when infrastructure is weak. (6) This may include significant disruption to victims’ lives, including injury and disability, grief and loss, loss of property, resources, social support, social networks, and displacement.

Mental health can be impacted at all timepoints surrounding extreme weather events –  during, after, and even beforehand. (4) Outcomes can range from minimal stress to clinical disorders, such as post-traumatic stress disorder (PTSD), depression, anxiety, substance use disorders, and suicidality (4). These impacts may manifest in the short term following a disaster, or continue on for the long term. (4) Mental health impacts following an extreme weather event may also provoke destructive behaviours such as sexual and other forms violence, which in turn may aggravate the mental health burden. (4)

Eco-Anxiety

People may experience a strong sense of fear and worry as a result of uncertainty related to climate change. (7) This may be categorized as “eco-anxiety” or “climate anxiety”. Individuals may find themselves distressed by news headlines about climate change and its impacts on human as well as non-human communities, such as habitat loss and species extinction. (4) It is generally pre-emptive rather than a response to a major climate-related event. It may manifest as anxious or depressive thoughts and feelings; however, it may also manifest in other ways, such as disordered eating. (8)

A closely related concept is solastalgia, characterized as the distress that people feel when environmental change impacts their connection to their home environment. (9) It is of particular concern for the well-being of Indigenous peoples and other land-dependent groups. (10)

Special Considerations for Mental Health

Individuals with a history of mental health concerns may be more likely to suffer adverse mental health as a result of extreme weather events and/or climate change more broadly. (APA 2017 in 4; 11). Certain neuroleptic and antidepressant medications have been hypothesized to impair core temperature modulation. (12) Thus, patients may be more susceptible to illness in conditions of extreme cold and, in particular, heat.

Action Strategy 1: Promote and engage in climate change activism

In the existing literature on eco-anxiety, there is an emphasis on clinicians engaging with their feelings about climate change, and activism is found to be protective (11, 13, 14, 15) In any case, there is a pressing need to decarbonize health care: if global health care were a country, it would be among the top 5 emitters – alongside the United States, China, and Russia. (16)(17) As a health care system, it is imperative that we fulfil our duty to “do no harm”: respond to the health impacts of climate change on health while mitigating our environmental footprint, rather than perpetuating the climate problem at hand.

Action Strategy 2: Encourage spending time in nature

Spending time in nature has been shown to relieve stress and promote environmental activism. It may also alleviate climate anxiety in some patients. (15, 18, 19) A number of clinical approaches have been proposed to respond to climate change; only a small number of observational studies assess their efficacy, so more research is needed. (15, 20)

Case Study: Impacts of Wildfires on Indigenous Communities

There have been a number of large-scale forest fires in Northern Canadian communities in recent years; and the impact of fires is expected to increase. (21) Around 80% of Indigenous communities in Canada are located in or adjacent to forest ecosystems that experience frequent fires. (22) As such, Indigenous people are among those most affected by wildfire evacuation. Forced displacement is associated with a number of mental health issues, including PTSD, anxiety, and depression. People evacuated from First Nations have been shown to face racism & discrimination, poor conditions, family separations and other difficulties in host communities, compounding the stress of evacuation. (22, 23)

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