Climate and Health

Versão em português

Extreme heat, vulnerability and Primary Health Care in Brazil.

Research on the health impacts of extreme heat in Brazil, conducted by Dr. Fábio Luiz Vieira, uses microdata from the Brazilian Mortality Information System (SIM) and meteorological records to estimate excess mortality during heat waves and to identify the groups and conditions associated with greater vulnerability.

This work combines environmental epidemiology with Primary Health Care. Its outputs so far include an original article in the Revista Técnico-Científica CEJAM, open-access datasets on Zenodo, an abstract submitted to the 26^th International Conference of Public Health Sciences (Bangkok, 2026) and a training course on heat-wave preparedness for primary care teams, currently in development.

Research on Heat Waves and Mortality in Brazil

More recently, his research has focused on the health impacts of extreme heat and heat waves in Brazil, particularly their association with mortality and the identification of groups and conditions associated with increased vulnerability.

One study, published in the Revista Técnico-Científica CEJAM, investigated excess mortality during the heat wave of 7–12 February 2024 in Paraná, Rio Grande do Sul and Roraima — the states identified by the National Institute of Meteorology (INMET) — using microdata from the Mortality Information System. Applying a time-stratified case-crossover design, the analysis observed 4,558 deaths against 4,341 expected (relative risk 1.077; 95% CI 1.039–1.117), approximately 217 excess deaths during this single event.

The excess was spread across almost all ICD-10 chapters rather than concentrated in any single group of causes, with no gradient by age or education. Notably, no deaths were attributed to exposure to excessive natural heat (ICD-10 X30), illustrating how heat-related mortality can remain invisible in cause-of-death statistics.

The datasets used in this study, together with a brief description of the analysis, have been made publicly available through Zenodo:

A second, larger study expanded this investigation to multiple heat-wave events in Brazil between 2014 and 2025. The analysis examined 3.7 million deaths and investigated whether specific medical conditions or causes of death modified the association between heat exposure and mortality.

The results provide further evidence that periods of extreme heat in Brazil are associated with diffuse excess mortality, while also identifying particularly relevant associations involving drowning deaths and individuals with dementia.

The underlying datasets and a summary of this research are also publicly available:

Conference submission: dementia and drowning as heat-related vulnerabilities

The findings of this second study have been submitted as an abstract — Dementia and Drowning as Heat-Related Vulnerabilities: Evidence from Brazilian Mortality Data — to the 26th International Conference of Public Health Sciences (ICCPHS 2026), organised by the College of Public Health Sciences, Chulalongkorn University, and to be held in Bangkok, Thailand, on 29 September 2026. The abstract is currently under review, and has been deposited as an open-access record with its own DOI.

The analysis applied a time-stratified case-crossover design to 3,672,003 deaths recorded in the Brazilian Mortality Information System across 12 states between January and May, 2014–2025, with daily maximum temperature derived from 568 automatic meteorological stations. Dementia showed the strongest evidence of increased susceptibility to hot days (interaction estimate 1.044; 95% CI 1.029–1.058), an association that persisted after restriction to adults aged 65 years and over and after stratification into 10-year age groups. By contrast, the conditions most often assumed to define heat vulnerability showed no evidence of greater susceptibility: obesity (1.000), diabetes (1.003), cardiovascular disease (0.992) and ischaemic heart disease (0.980).

Among external causes, drowning showed the largest association with hot days (RR 1.161; 95% CI 1.117–1.208). Risk increased across temperature deciles, peaked on the day of exposure itself, and was strongest among adults aged 15–39 years and for drownings in natural waters.

These patterns are compatible with two distinct behavioural pathways: an impaired capacity to recognise and respond appropriately to heat among people with dementia, and increased exposure to natural waters during hot weather. The ecological temperature measure and potential confounding by precipitation and mobility limit causal interpretation, but the findings support considering both dementia and drowning prevention within heat-health warning strategies.

Together, these studies contribute to an important question for climate and health research in Brazil: who is actually dying during periods of extreme heat, and which groups are most vulnerable in the Brazilian context?

International literature has identified several clinical and demographic groups as potentially vulnerable to extreme heat. However, these associations cannot simply be assumed to have the same magnitude or distribution in Brazil. Climate, housing, socioeconomic conditions, population characteristics, healthcare access and patterns of disease differ substantially between countries and regions.

Brazilian mortality and environmental data therefore provide an opportunity to determine whether internationally recognised risk factors are reproduced locally and, importantly, to estimate the magnitude of their impact within the Brazilian population.

These analyses represent initial steps towards quantifying a burden that is often difficult to identify through conventional mortality statistics alone: deaths associated with extreme heat may increase substantially during heat waves even when heat itself is not recorded as the underlying cause of death.

Clinical and Field Background

A Family Physician by training, Dr. Vieira began his career in Brazil’s Family Health Programme (Programa Saúde da Família), providing care to communities in peripheral urban areas, where inadequate housing, overcrowding, limited infrastructure and socioeconomic vulnerability had a direct impact on health. This experience reinforced a fundamental principle of Primary Health Care: health outcomes are shaped not only by diseases and individual behaviours, but also by housing, territory, occupation, access to resources and the broader environment in which people live.

His subsequent work in Angola, supporting the implementation of a community health worker programme, provided another perspective on environmental vulnerability. Communities affected by drought, difficulties in accessing safe water and limited healthcare infrastructure illustrated how environmental conditions can influence both exposure to disease and the capacity of individuals and communities to protect their health.

These experiences have acquired increasing relevance in the context of climate change. Extreme heat, drought, water insecurity and other climate-related events do not affect populations equally. Their health consequences interact with age, chronic diseases, medications, occupation, housing conditions, access to healthcare and socioeconomic circumstances.

From Epidemiological Evidence to Primary Care

Understanding this burden has practical implications. Identifying which populations experience increased mortality during heat waves can support the development of targeted prevention strategies, public health alerts and preparedness measures within healthcare services.

Primary Health Care has a particularly important role in climate adaptation. Primary care teams understand patients not only through their diagnoses, but also through their families, medications, occupations, housing conditions and communities. This creates an opportunity to identify vulnerability before an extreme event occurs and to implement preventive interventions for individuals at greater risk.

Ongoing preparedness work: a heat-wave course for primary care teams

One practical translation of this evidence, currently in development, is a short training course for Brazilian primary care teams — Ondas de Calor e Saúde: Preparação para Eventos de Calor Extremo (Heat Waves and Health: Preparedness for Extreme Heat Events). The proposal is an introductory course of approximately 43 minutes across five short lessons, aimed at physicians, nurses and community health workers in Primary Health Care. It assumes no prior background in climate science or environmental epidemiology.

It is structured around what a primary care professional needs to recognise and do before and during a heat alert:

• What a heat wave is, and why it is a health problem (7 min) — including why no single universal threshold defines one
• How heat affects the body (8 min) — the strain thermoregulation places on the cardiovascular, renal, respiratory and central nervous systems
• Who is at greatest risk (9 min) — exposure and sensitivity, including the role and the uncertainties of commonly used medications
• Recognition and management of heat-related illness (11 min) — heat cramps, heat exhaustion and heat stroke; initiating cooling and deciding when to refer
• Prevention and service preparedness (8 min) — concrete measures for the health unit and communication with the population during a heat alert

A deliberate feature of the course is that it separates three situations frequently conflated in practice: the epidemiological association between heat and mortality, the worsening of pre-existing disease, and illness directly caused by heat — while remaining explicit about the limits of what the available evidence supports.

Current Research Interests

• Heat waves and excess mortality
• Clinical and social vulnerability to extreme heat
• Chronic diseases and heat-related risk
• Climate change and Primary Health Care
• Preparedness of health services for extreme weather events
• Climate-related health inequalities
• Digital health to support climate-resilient healthcare systems

This work sits at the intersection of climate and health, epidemiology, Primary Health Care and digital health, with an emphasis on translating Brazilian population-level evidence into practical strategies for prevention, preparedness and healthcare delivery.

Climate & Health Membership

Member of the Climate Health Society — an international society bringing together clinicians and researchers working on the health impacts of climate change. LMIC membership, active since August 2026.