Health Research Takes a Carbon Toll

According to the US-based ClinicalTrials.gov, more than 40,000 new clinical trials are launched globally each year. Few are required to address their environmental impacts, but these impacts are not minor. A single clinical trial on the effectiveness of dapagliflozin in reducing heart failure and death, for example, emitted about 2,500 metric tonnes of carbon dioxide through travel and other impacts – equivalent to the annual output of 500 cars. Health research is also contributing to the rapid increase in demand for energy-intensive computation and data centres, a major source of greenhouse gas emissions and other impacts.

Professor Chinmoy Sarkar has been investigating climate change and health from both ends of this conundrum. His recent health research with postdoctoral fellow Dr Ka Yan Lai and others traced the effects of temperature extremes on youth mental illness and general hospitalisations. He is also part of a 16-member international study led by the UK Academy of Medical Sciences and the US National Academy of Medicine to consider the bigger picture of the sustainability of health research.

“When we think about the climate costs on human health, for health research, it should be a matter of two-way accounting. We talk about climate change and its extremes that produce direct and indirect impacts on health. But our research in multiple health sectors also constitutes one of the human activities responsible for increasing greenhouse gases and the frequency and intensity of climate extremes,” he said. “We need to embed sustainability practices within research to reduce incurring an additional burden on our health.”

Pathways to greener research

The international report, For People, For Planet: Improving the Environmental Sustainability of Health Research, identifies six areas where greener practices could be introduced.

One is data metrics and information and the need to better quantify environmental impacts. There is as yet no understanding of the overall carbon impact of health research, let alone other impacts such as waste and water, he said.

Funding bodies could also promote sustainability by requiring researchers and institutions to meet minimum sustainability assessment criteria in order to secure grants.

The regulatory and health research governance framework could also play a role by integrating greener standards into their processes – something Professor Sarkar believes could promote research innovation, such as the remote collection of study data via sensors and the shared use of data resources across institutions, as seen with the UK Biobank.

The other three areas offer opportunities to improve environmental sustainability through better standards and training – procurement and supply chains, energy-efficient physical infrastructure, including buildings and data centres, and capacity building among researchers.

Professor Sarkar noted these measures were not all easily agreed upon by the report’s multidisciplinary authors and were subjected to intense debate and reflection before consensus was reached. One issue that stands out for him is concern about a two-row above system, where high-income institutions and countries have the resources to invest and comply with sustainability measures, but poorer ones do not. Flexibility and equitable support for capacity-building are therefore needed.

In any case, the report is meant to be a wake-up call for the research community and practitioners. “We want to instil the fervour, start a discussion. Clinical and health research endeavours can risk-proof our health. But we need to do so in a way that is sustainable,” he said.

The harm caused by weather extremes

Professor Sarkar and Dr Lai had two studies published this year showing the effects of extreme and variable temperatures on human health, with some alarming results.

A review in npj Mental Health Research, comprising 28 observational studies on heat exposure and mental health in more than 30,000 children and adolescents from 2007 to 2025, found that each one degree Celsius increase in ambient temperature was associated with a one per cent higher risk of suicide. Relative to low temperature, high temperature exposure was associated with a 12–18 per cent higher risk of hospitalisation for mental health disorders, schizophrenia, depression and all mental health conditions combined among 1.18 million individuals. The studies were conducted mostly in higher-income countries. “The evidence suggests the need for preventive interventions and heat action plans, but equally important is the need to gather evidence in lower-income countries, too,” he said.

The findings of another empirical study published in Communications Medicine, comprising about 500,000 participants in the UK Biobank, plug a gap in quantifying associations between ambient temperature, temperature changes, and all hospitalisations. High summer temperatures were associated with more admissions for kidney and heat-related disorders. Mild winters were associated with more hospitalisations for any cause, particularly cardiovascular diseases, mental disorders and heat-related illness. Dr Lai said this may be attributed to modified health-seeking behaviours in milder winters and physiological responses among residents acclimatised to cold winters.