Temperature Extremes and Human Health in Cyprus: Investigating the Impact of Heat and Cold Waves

Climate change poses a substantial threat to both the Earth’s ecosystems and human society. In
Mediterranean countries like Cyprus, extreme temperatures and especially heatwaves during summer
months are increasingly common as it is observed in the past years due to anthropogenic climate
change. While cold waves are less frequent, they also pose significant health risks, as some studies
show that more deaths actually occur during cold weather than hot, especially in warmer cities
(southern) rather than colder (northern) in Europe. Extreme temperatures leads to heightened
bio-climatic stress and can adversely affect the human body, disrupting physiological functions and
exacerbating preexisting health conditions, ranging from discomfort and severe illnesses that require
hospitalization to mortality.
This study examines temperature trends in Cyprus over the past four decades, focusing on extreme
temperature events from 2000 to 2019. Using ERA5-Land reanalysis data, we analyzed both maximum
and minimum daily temperatures for both the warm (May-Oct) and the cold (Nov-Apr) season.
Extreme hot days were defined as those where both maximum and minimum temperatures exceeded
the 95th percentile of each month in the warm season. Conversely, extreme cold days were defined as
those where both temperatures fell below the 5th percentile in the cold season. Our analysis revealed
an upward trend in temperatures over the past four decades, with a statistically significant increase
in the number of extreme hot days and a decrease in extreme cold days for the last 20 years. Statistical
and machine learning methods, including Distributed Lag Models (DLMs) and Generalized
Additive Models (GAMs), were employed to estimate mortality and morbidity risks over a 21-day lag
period using health statistics from Ministry of Health and Statistical Service in Cyprus. We observed
a notable increase in mortality risk associated with both high and low temperatures extremes. In
contrast, the morbidity risk showed a different profile; overall morbidity risks were lower compared
to mortality and the maximum risk occurred at lower temperatures. In general, lower temperatures
exhibited pronounced health risks compared to higher temperatures. Additionally, we calculated
the optimal temperatures that corresponded to the lower risk as well as the attributable fraction of
deaths and hospitalizations for extreme temperature days and extreme temperature events, lasting
from two or more consecutive days. The findings indicated that both deaths and hospitalizations
were notably higher during the cold period in comparison to the warm period. Nevertheless, during
periods of extreme high temperatures, the rate of increase in attributable deaths was greater than
during the cold period when compared to days with non-extreme temperatures.