INVESTIGATING THE ASSOCIATION BETWEEN AMBIENT AIR QUALITY, HEAT INDEX, AND STROKE HOSPITAL ADMISSIONS IN QATAR, DOHA: A RETEROSPECTIVE TIME-STRATIFIED CASE-CROSS OVER ANALYSIS

Abstract

Background: Stroke is a significant cause of death and disability globally, with new evidence associating its incidence with environmental variables. The influence of ambient air quality and heat on acute stroke admissions in Qatar, a nation marked by severe temperatures and recurrent dust storms, is emerging as a significant public health concern. This research seeks to examine the short-term associations between air pollution and heat index and their effect of the daily stroke admissions in Doha, Qatar Methods: Hospital records of 14025 stroke patients were obtained from the neuroscience institute of Hamad General Hospital, and each case day was matched with control days selected from the same month, year, and day of the week. Air quality and meteorological data including daily levels of PM2.5, NO2, O3, Heat and heat index were obtained from Qatar Energy and Environmental research institute and linked to each admission date. Frequency and frequency percentages for stroke subgroups were calculated, normality tests using Q_Q plots and Kolmogorov-Smirnov test, Spearman correlations for stroke admissions with other health variables and the association between stroke admissions across different subgroups were modeled using the Poisson regression model. The daily and annual mean, standard deviations (SD), minimum (Min), the 2.5th (P2.5), 25th (P25), 75th (P75), and 97.5th (P97.5) percentiles, and interquartile range (IQR) of the collected air pollutants and meteorological data were calculated. The monthly variations in air pollutants NO2, O3, PM2.5, and two meteorological factors (temperature and relative humidity) in Doha, Qatar during 2018 to 2023 were visualized by creating trend plots for each pollutant. Pearsons's correlation coefficients were calculated to assess the magnitude and direction of the associations between air pollutants and meteorological variables. A retrospective time stratified case-cross over study design and analysis was used to analyze the association between air pollutants of fine particulate matter (PM2.5), nitrogen oxides (NO2), ozone (O3), meteorological factors (heat and heat index) and stroke admissions from 2018 to 2023. Conditional Quasi Poisson Logistic regression models estimated the relative risk of stroke admission associated with air pollutants, heat and heat index levels. Accounting for lagged effects, seasonal trends. Subgroup analysis by age, gender, stroke type, body mass index levels, smoking status, diabetes and hypertension, was performed to identify vulnerable groups. AirQ+ software was used to assess PM2.5 impact and burden on stroke admissions. Results: The study findings indicate that exposure to air pollutants and meteorological factors were significantly associated with increased risk of stroke hospital admissions in Doha, Qatar. The Poisson regression model showed that for every 10-unit increase in air pollutants, the incidence rate ratio (IRR) for stroke admissions was highest for Ozone O3 at 1.10 (95% CI: 1.00, 1.20), followed by nitrogen dioxide (NO2) at 1.01 (95%CI: 1.003. 1.02, and fine particulate matter at 1.003 (95% CIL 1.001, 1.005). These results suggest a statistically significant impact of air pollution on stroke admissions. The exposure -response relationship revealed that relative risks (RR) per 10-unit increase in PM2.5, NO2, and O3 at lag 0 were 1.01 (95% CI: 1.00, 1.19), 1.00 (95% CI: 1.00, 1.02), and 1.03 (95% CI: 1.01. 1.05), respectively. Among subgroups, diabetic individuals exhibited the highest RR associated with PM2.5 at 1.02 (95% CI: 1.00, 1.04) at lag 0. Indicating that stroke admissions increased by 2 % among those with diabetes on the same day of exposure. Similarly, NO2 had the greatest effect on females, with RR of 1.04 (95% CI: 1.00, 1.08) at lag 1, with 4 % increased risk one day after exposure. Extreme heat index value was associated with the highest stroke risks among females, where the RR was 3.5 (95% CI: 1.40, 9.00) at the 99th percentile (63.9 °C) on the same day of exposure. Conclusion: This study investigated the association between air pollution and heat index, and stroke admissions in Doha from 2018 to 2023. Findings showed that PM2.5, NO2, and O3 levels were above the WHO air quality guidelines and were significantly associated with increased risk of stroke hospital admissions, specifically among vulnerable groups such as older adults. Extreme heat exposure and high heat index further elevated stroke hospital admission risk. The AirQ+ analysis estimated that PM2.5 contributed to 2 % of stroke -related admissions emphasizing the need for urgent air quality improvements. Strict air pollution control measures, enhancing urban planning to mitigate heat exposure, and improving public awareness are needed to reduce stroke hospital admissions. Additionally, long-term cohort studies assessing chronic exposure impacts are needed to assess chronic exposure impacts, as well as expanding air monitoring network are needed to refine the results.