1.0 Introduction
Individual extreme heat events (EHEs) can be associated with hundreds to
thousands of excess deaths (Kovats & Hajat, 2008), with the most severe
example being the approximately 70,000 excess deaths across Europe in
the summer of 2003 (Robine et al., 2008). The frequency and intensity of
EHEs are expected to increase in the coming decades because of climate
change, and global temperature extremes have already become more
frequent since the 1950s (Ebi et al., 2021; IPCC, 2021). Consequently,
it is essential to understand who is at risk of dying during EHEs to
help develop interventions to prevent future heat-related mortality.
Susceptibility to the health effects of high temperatures varies between
individuals. For example, older adults have an increased risk of death
because thermoregulation and the ability to recognize thermal stimuli
deteriorate with age (Ebi et al., 2021; Kenny et al., 2018). Other
factors associated with an increased risk include pre-existing
cardiovascular disease (Ebi et al., 2021) and mental illness (J. Liu et
al., 2021) as well as material deprivation (Kovats & Hajat, 2008) and
social isolation (Kenny et al., 2019). Age, cardiovascular disease,
respiratory disease, and diabetes are often cited as primary risk
factors for heat-related illness or death and are generally referenced
in public health messaging (Centers for Disease Control and Prevention,
2017; Ebi et al., 2021; Kenny et al., 2018). However, the risk of
heat-related death varies over space and time as community
characteristics, adaptation strategies, behaviors, and
socio-demographics change. Further, EHEs may also co-occur with other
environmental stressors such as high levels of ground-level ozone and
particulate matter from wildfires (Rahman et al., 2022). Therefore, it
is important to understand factors associated with the risk of death
during specific EHEs to develop more targeted strategies to protect the
health of susceptible populations in different regions.
Western North America experienced an unprecedented EHE in late June
2021, which was rapidly attributed to climate change (Philip et al.,
2021). During this event, there was a 95% increase in population
mortality across British Columbia (BC), Canada, equivalent to
approximately 740 excess deaths, making it one of the deadliest weather
events in Canadian history (Henderson et al., 2021). Early research from
the BC Centre for Disease Control (BCCDC) found that community deaths in
greater Vancouver were associated with neighborhood deprivation and
decreased neighborhood greenness (Henderson, McLean, et al., 2022). In
this follow-up study, we aim to assess the relationship between chronic
diseases and the risk of death during the 2021 EHE. We compare all
adults who died in BC during the EHE with all adults who died on the
same dates in the previous nine years to examine differences in the
prevalence of 26 chronic diseases between the two groups.