Extreme temperature and out-of-hospital-cardiac-arrest. Nationwide study in a hot climate country

Abstract

Background Out-of-hospital-cardiac arrest (OHCA) is frequently linked to environmental exposures. Climate change and global warming phenomenon have been found related to cardiovascular morbidity, however there is no agreement on their impact on OHCA occurrence. In this nationwide analysis, we aimed to assess the incidence of the OHCA events attended by emergency medical services (EMS), in relation to meteorological conditions: temperature, humidity, heat index and solar radiation. Methods We analyzed all adult cases of OHCA in Israel attended by EMS during 2016–2017. In the case-crossover design, we compared ambient exposure within 72 h prior to the OHCA event with exposure prior to the four control times using conditional logistic regression in a lag-distributed non-linear model. Results There were 12,401 OHCA cases (68.3% were pronounced dead-on-scene). The patients were on average 75.5 ± 16.2 years old and 55.8% of them were males. Exposure to 90th and 10th percentile of temperature adjusted to humidity were positively associated with the OHCA with borderline significance (Odds Ratio (OR) =1.20, 95%CI 0.97; 1.49 and OR 1.16, 95%CI 0.95; 1.41, respectively). Relative humidity below the 10th percentile was a risk factor for OHCA, independent of temperature, with borderline significance (OR = 1.16, 95%CI 0.96; 1.38). Analysis stratified by seasons revealed an adverse effect of exposure to 90th percentile of temperature when estimated in summer (OR = 3.34, 95%CI 1.90; 3.5.86) and exposure to temperatures below 10th percentile in winter (OR = 1.75, 95%CI 1.23; 2.49). Low temperatures during a warm season and high temperatures during a cold season had a protective effect on OHCA. The heat index followed a similar pattern, where an adverse effect was demonstrated for extreme levels of exposure. Conclusions Evolving climate conditions characterized by excessive heat and low humidity represent risk factors for OHCA. As these conditions are easily avoided, by air conditioning and behavioral restrictions, necessary prevention measures are warranted.

Heatwave Definition and Impact on Cardiovascular Health: A Systematic Review

“…The most frequently used meteorological measure as heat indicator was air TEMP, applied in 56 of 57 cases. In nine studies, air TEMP was included in the computation of more complex indices, such as “Apparent Temperature” [ 42 , 53 , 60 , 71 , 76 , 83 ], “Perceived Temperature” [ 39 ], “Pseudo-equivalent daily temperature” [ 88 ] or “Discomfort Score” [ 56 ], by combining it with relative humidity, water vapor pressure, dew point TEMP, wind speed and/or heat radiation. The relevant calculation formulas are summarized in Table 2 , except for “Perceived Temperature” [ 39 ] as it was not provided in the relevant study.…”

“…The median observation period was 10 years, with a minimum of 2 years for Israel [ 56 ], Slovenia [ 88 ] and a Chinese study [ 83 ], and a maximum of 28 years for Germany [ 57 ]. Several studies ( n = 22; 40.7%) analyzed the influence of heat only in an arbitrarily defined warmer period of the year, beginning within March–June and ending within June–October for the Northern Hemisphere, while spanning from September-November to March for the Southern Hemisphere.…”

“…Among the 13 (24.1%) studies for which the events’ location or patients’ home address were available, only two [ 48 , 56 ] associated them with the meteorological conditions at the event time, while Jiang et al [ 86 ] linked the TEMP with that at the hospital location, as the majority of patients did not report their complete address.…”

Progress on the Impact of Climate Change on Cardiac Arrest

“…Currently, when studying temperature associated with the risk of sudden cardiac death, extensive epidemiological studies have shown the presence of the J or U type between temperature and the occurrence of OHCA [1,2], Suggesting that either too high or too low temperatures can raise the risk of OHCA. A single Israeli case-crossover study of temperature and cardiac arrest showed that [3], High temperature and low humidity are the risk factors for OHCA. In a study of 29,671 OHCA patients in China, high temperature, heat wave, cold temperature and cold wave were all associated with the risk of OHCA, and the effect of low temperature on OHCA was significantly higher than high temperature [4].…”

“…The risk of death increases in extreme heat or humid heat. In a prospective study from Germany in out-of-hospital cardiac arrest, results indicated an association between relative humidity and OHCA for cardiac cause, especially in dry air [9]; And a national case-crossover study in hot countries in Israel showed that OHCA was more likely to be exposed with higher humidity conditions [3]; In a large time series study in South Korea, relative humidity was an important meteorological factor in the occurrence of OHCA and was negatively associated with OHCA in the effect of exposure lag [10]. There are few studies on the impact of relative humidity on the risk of sudden death, and humidity is susceptible to temperature changes.…”