Daily Meteorological Parameters Influence the Risk of Intracerebral Hemorrhage in a Subtropical Monsoon Basin Climate

Short-term environmental triggers of hemorrhagic stroke

Hemorrhagic stroke (HS) is associated with severe morbidity and high mortality. Identifying the trigger factors for HS is critical for disease prevention. This study aimed to assess the associations between short-term environmental triggers (STETs) and HS risk. We systematically searched six databases for articles published up to September 9, 2022. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using random-effect models to evaluate the associations between STETs and the risk of HS. Heterogeneity was assessed using Cochran Q and I2 tests. A total of 63 studies were included for analysis. Of these, 40 focused on air pollutants and 23 on meteorological factors. Pooling results showed that exposure to particulate matter 2.5 (PM2.5; OR, 1.003 per 10 μg/m3; 95% CI, 1.001-1.007), sulfur dioxide (SO2; OR, 1.022 per 10 ppb; 95% CI, 1.005-1.040), and nitrogen dioxide (NO2; OR, 1.026 per 10 ppb; 95% CI, 1.004-1.047) was associated with an increase in HS risk. Moreover, exposure to PM2.5 (OR, 1.018 per 10 μg/m3; 95% CI, 1.009-1.027) and SO2 (OR, 1.102 per 10 ppb; 95% CI, 1.010-1.204) was positively associated with the risk of intracerebral hemorrhage. In addition, extreme temperature, high pressures, high and low relative humidity were potentially associated with HS risk. Targeted preventive measures to limit the effect of these air pollutants and extreme meteorological factors should be taken to reduce the HS disease burden. Further studies are warranted to verify these findings.

Cleaner outdoor air diminishes the overall risk of intracerebral hemorrhage but brings differential benefits to subpopulations: a time-stratified case-crossover study

BACKGROUND

Short-term air pollution exposure and intracerebral hemorrhage (ICH) risk are related. However, the impact of the pollutant levels decline on this relationship, which attributes to clean air policy implementation and the COVID-19 pandemic lockdown, is unclear. In the present research, we explored the influence of different pollutant levels on ICH risk during eight years in a southwestern China megacity.

METHODS

Our research used a time-stratified case-crossover design. We retrospectively analyzed ICH patients in a teaching hospital from January 1, 2014, to December 31, 2021, and divided 1571 eligible cases into two groups (1st group: 2014-2017; 2nd group: 2018-2021). We observed the trend of every pollutant in the entire study period and compared the pollution levels in each group, using air pollutants data (PM2.5, PM10, SO2, NO2, CO, and O3) documented by the local government. We further established a single pollutant model via conditional logistic regression to analyze the association between short-term air pollutants exposure and ICH risk. We also discussed the association of pollution levels and ICH risk in subpopulations according to individual factors and monthly mean temperature.

RESULTS

We found that five air pollutants (PM2.5, PM10, SO2, NO2, CO) exhibited a continuous downward trend for the whole duration, and the daily concentration of all six pollutants decreased significantly in 2018-2021 compared with 2014-2017. Overall, the elevation of daily PM2.5, SO2, and CO was associated with increased ICH risk in the first group and was not positively associated with risk escalation in the second group. For patients in subgroups, the changes in the influence of lower pollutant levels on ICH risk were diverse. In the second group, for instance, PM2.5 and PM10 were associated with lower ICH risk in non-hypertension, smoking, and alcohol-drinking participants; however, SO2 had associations with increased ICH risk for smokers, and O3 had associations with raised risk in men, non-drinking, warm month population.

CONCLUSIONS

Our study suggests that decreased pollution levels diminish the adverse effects of short-term air pollutants exposure and ICH risk in general. Nevertheless, the influence of lower air pollutants on ICH risk in subgroups is heterogeneous, indicating unequal benefits among subpopulations.