A new and first-of-its-kind study in Israel by the Taub Center found that during weeks of high heat stress, there was an increase in emergency department visits due to respiratory diseases, cardiovascular diseases and kidney diseases, compared with weeks when heat stress levels were lower.
During periods of severe heat stress, emergency department visits increased by 41% among patients diagnosed with pulmonary disease, by 28% among patients with kidney disease, and by 18% among patients with cardiovascular disease.
The rise in global average temperatures has been reflected, among other things, in an increase in the number of unusually hot days and nights each year. Over the years, studies have found a link between heat stress and higher rates of illness, increased use of healthcare services and excess mortality, particularly among vulnerable populations. A new study by researcher Or Siman Tov, Professor Alex Weinreb, Irena Rogozovsky and Dr Maya Sadeh focused on the chronic conditions most sensitive to heat stress—cardiovascular disease, kidney disease and respiratory illnesses.
The researchers analysed data on emergency department visits, hospital admissions and deaths related to these conditions between 2010 and 2023.
Analysis of the Israeli data found a positive correlation between the rate of emergency department visits and the summer heat stress index, a measure that combines temperature and humidity, for almost all medical diagnoses.
As noted, weeks with high heat stress were associated with a statistically significant increase in emergency department visits for respiratory, cardiovascular and kidney diseases compared with weeks experiencing lower heat stress.
However, the increase in emergency visits for respiratory and cardiovascular conditions during periods of heat stress was greater in 2010–2017 than in 2018–2023. This finding may point to a gradual process of adaptation by Israel’s population to increasing heat stress.
In addition, the gap in emergency department visit rates between periods of high and low heat stress was greater in communities with higher socioeconomic rankings than in those with lower socioeconomic rankings—a finding that runs counter to results from similar studies conducted elsewhere in the world.
The researchers suggest that one possible explanation is the greater reliance on air conditioning among more affluent populations in Israel, which may reduce their ability to adapt to periods of extreme heat.
Another possible explanation lies in the geographical proximity of these populations to hospitals: since many of them live in central Israel, where there is a higher concentration of medical centres, they are more likely to seek emergency care when symptoms appear.
In contrast, patients from peripheral regions and lower socioeconomic backgrounds may be less likely to do so and may instead rely on home treatment. Geographically, the study found that in the Tel Aviv, Central and Jerusalem districts, the increase in emergency department visits due to heat stress was higher than in other parts of the country, particularly in relation to respiratory illnesses.
The researchers also found that as heat stress increases, hospital stays become longer. However, they found that excess mortality among patients hospitalised due to heat stress is relatively low, amounting to fewer than two additional deaths per year (out of an average of approximately 40,000 to 53,000 deaths annually throughout the study period).
The researchers qualified this finding, emphasising that the study examined only deaths occurring within hospitals, and did not include deaths outside hospitals that may also be linked to heat stress. This is particularly relevant for heart patients, who may not survive long enough to reach a hospital (and therefore, the heart patients who do reach hospitals may actually be those with less severe conditions).
The researchers estimated that the additional cost to the healthcare system resulting from rising heat stress levels (in relation to the specific diseases examined, which did not include conditions such as dehydration or heatstroke) stands at approximately NIS 380 million over a decade.
According to the researchers, an increase of one unit in the heat stress index leads to approximately 5,500 additional hospitalisation days per year for the diseases examined. Between 2014 and 2025, the summer months saw an average increase of around two units in heat stress levels.
It should be noted that the cost to the economy resulting from these additional hospitalisation days is even higher.
In light of the study’s findings, the researchers recommend that the healthcare system increase its preparedness during the summer months and in weeks of extreme heat stress, while also expanding preventive healthcare efforts within the community.
They also emphasise the importance of continuing research in this area, with particular attention to geographical disparities and differences between population groups in rates of emergency department visits.