Risk and protective factors for heat-related events among older adults of Southern Quebec (Canada): The NuAge study

OBJECTIVES: Extreme heat is known to increase heat-related health outcomes (HRHO). Incidence and predictors of HRHO were examined among older adults living in Quebec (Canada). METHOD: This prospective five-year study used data from the first follow-up of community-dwelling older adults from the NuAge cohort (2005-2006), located in three health regions of Southern Quebec. Medical, social and environmental factors, identified in Health Canada guidelines (2011), were used to develop the Older Adult Health Vulnerability Index (OAHVI). HRHO, obtained from a medico-administrative database, were defined as events occurring on a hot day (maximal temperature >= 30 degrees C) between 2006 and 2010. Two outcomes were examined: heat-related 1) emergency department presentations (EDPs) and 2) health events (i.e., EDP, hospitalizations or deaths). Multivariate logistic regressions were performed to assess the associations between risk and protective factors, including OAHVI, and both outcomes. RESULTS: EDP and hospitalizations were, respectively, 2.6 (95% CI: 2.0-3.5) and 1.7 (95% CI: 1.1-2.6) times more frequent on hot days compared to normal summer days. Low household income and disability increased risk of heat-related EDP (AOR = 3.20; 95% CI: 1.16-8.81 and AOR = 2.66; 95% CI: 1.15-6.14 respectively) and health events (AOR = 2.84; 95% CI: 1.06-7.64 and AOR = 2.51; 95% CI: 1.13-5.61 respectively). High social participation was a protective factor of heat-related EDP (AOR = 0.05; 95% CI: 0.01-0.20) and health events (AOR = 0.04; 95% CI: 0.01-0.18). Older adults presenting >= 6 OAHVI factors out of 9 were 7-8 times more at risk of heat-related EDP (OR = 7.40; 95% CI: 1.51-36.19) and health events (OR = 7.77; 95% CI: 1.63-37.20) compared to participants having 0-1 factor. CONCLUSION: Social participation, reduced autonomy and low income were predictors of HRHO. The OAHVI, also a strong predictor, should help clinicians identify high-risk elderly patients.