Extreme hot weather events and risk of hospitalisation for cardiovascular and respiratory diseases in older people in Hong Kong in 2012 to 2018

Background: The older population is more vulnerable to the impact of extreme hot weather events (EHWEs), while the impact on the frailer institutionalised older population was seldom assessed. Our objective was to assess the relationship between EHWEs and hospitalisation risks among institutionalised and community-dwelling older people.

Methods: We used territory-wide hospitalisation record of Hong Kong from year 2012 to 2018 to assess the associations between EHWEs and cardiovascular and respiratory disease hospitalisations in the population aged 65 or above. A very hot day (VHD) was defined as the daily maximum temperature ≥ 33°C, and a hot night (HN) was defined as the daily minimum temperature ≥ 28°C. We assessed whether prolonged exposure to high temperatures (defined as 3 consecutive VHDs (3VHD) or HNs (3HN)) was related to higher risk of hospitalisation over a lag period of 0-21 days. Time-stratified case-crossover design was used. Analyses were stratified by old age home (OAH) residence status.

Results: Exposure to 3VHDs was related to higher risk of cardiovascular disease admissions for community-dwelling older people [relative risk (RR): 1.09; 95% confidence interval (95%CI): 1.03 to 1.14 (lagged 4 days, i.e. delayed manifestation up to 4 days)] while for OAH residents, the association could have a lag of 18 days (RR: 1.28; 95%CI 1.05 to 1.54). For respiratory disease admissions, such relatively long delayed relationship was not clearly observed.

Conclusions: The warming climate could increase healthcare demand in the long run. Frailer patients could present with a generally more marked and delayed onset of cardiovascular disease aggravation than the community-dwelling population.