Effects of meteorological factors and air pollutants on hospitalization volume of ischemic heart disease in Urumqi City

Background The effects of meteorological factors and air pollutants on ischemic heart disease (IHD) hospitalizations in Urumqi have not been fully understood.

Objective To investigate the effects of meteorological conditions (temperature, relative humidity) and common air pollutants fine particulate matter (PM_2.5), inhalable particulate matter (PM₁₀), ozone (O₃), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO) on the daily hospitalization volume of IHD, and to provide a scientific basis for the development of targeted prevention and management strategies.

Methods Basic information of 90622 IHD hospitalized patients in Urumqi City was collected from January 1, 2014 to December 31, 2022, and daily air pollutant concentration data and meteorological data were collected during the same period. The meteorological data included daily mean temperature, daily maximum temperature, daily minimum temperature, and daily mean relative humidity, and the common air pollutants included PM_2.5, PM₁₀, daily maximum 8-h average concentration of O₃ (O₃_8 h), SO₂, NO₂, and CO. Descriptive statistical analyses (mean, standard deviation, and quartiles) were performed on the collected data. A distribution lag nonlinear model (DLNM) based on time-stratified case-crossover design was established to estimate the lagged effects (RR) as well as the cumulative lagged effects (RR_cum) of daily mean temperature, relative humidity, and different air pollutants on the number of IHD admissions, stratified by gender and age (<60 and ≥60 years). Subsequently, a generalized additive model (GAM) was used to explore the effects of cold waves (≤ P₅ of the daily minimum temperature and lasting ≥3 d) versus heat waves (≥ P₉₅ of the daily maximum temperature and lasting ≥3 d) on IHD hospitalizations and the potential interactions between temperature and the more influential air pollutants particulate matter (PM) and O₃_8 h on IHD hospitalizations.

Results The maximum number of IHD hospitalizations in a single day in Urumqi from January 1, 2014 to December 31, 2022 was 100, and the average daily number of hospitalized IHD patients was 27. Daily mean temperature, relative humidity, and air pollutants had different nonlinear relationships and hysteresis with IHD hospitalizations. Extremely low temperatures (<P₁: −18 °C) showed the greatest risk to admission for the total IHD population at a cumulative lag of 31 d (lag0-31) (RR_cum=2.092, 95%CI: 1.261,3.471). Female lag0-31, RR_cum and 95%CI: 3.416 (2.296,5.082) and people ≥60 years old lag0-31, RR_cum and 95%CI: 2.356 (1.681,3.303) were more sensitive to extremely low temperatures. The risk of IHD hospitalization was greatest on lag20 for cold waves (RR=1.242, 95%CI: 1.053, 1.465), and no lagged effect of heat waves on the number of IHD hospitalizations was found. There was a positive interaction (SI >1, P<0.001) between temperature, PM, and O₃_8 h on the risk of IHD hospitalization, especially for low temperature-high PM and O₃_8 h.

Conclusion Both low temperature and high pollutant concentrations associate with an increase in IHD hospitalizations with lagged effects in Urumqi from 2014 to 2022, while cold waves associate with a higher risk of IHD admissions. Females and people aged 60 years and older are at high risk.