Considerable Impact of Major Air Pollutants on Hypertension in Guizhou Province, Southwest China
Air pollution is a significant public health concern, with well-documented effects on respiratory and cardiovascular diseases (CVDs). Particulate matter, especially fine particles less than 0.1 µm, can penetrate the blood-brain barrier, reaching the brain and central nervous system, leading to physiological and pathological changes. Long-term exposure to fine particulate matter (PM2.5) has been shown to increase the risk of CVDs among Chinese residents. Additionally, even short-term exposure to low concentrations of air pollutants can trigger acute coronary syndrome within an hour. A meta-analysis based on seven databases revealed a positive correlation between environmental air pollution and elevated blood pressure, as well as hypertension. Mounting evidence suggests that air pollution significantly impacts cardiovascular and cerebrovascular health.
Guizhou Province, located in southwest China, has a unique geographical location, lifestyle, and economic development level that contribute to a lower prevalence of hypertension compared to other provinces. The region benefits from relatively light air pollution, extensive green coverage, and generally good air quality. However, exposure to low concentrations of air pollutants still poses health risks. This study aims to explore the relationship between hypertension prevalence and four major air pollutants—sulfur dioxide (SO2), nitrogen dioxide (NO2), PM2.5, and particulate matter (PM10)—in Guizhou Province. The findings provide a foundation for preventing and controlling hypertension related to air pollution.
The study collected monthly concentrations of SO2, NO2, PM2.5, and PM10 in Guizhou Province from January 2016 to December 2021 through the Monthly Report on Environmental Quality of Guizhou Province, issued by the Department of Ecological Environment of Guizhou Province. The observation cities included Guiyang, Zunyi, Tongren, Bijie, Qiannan, and Qianxinan. Data on the CVD status of residents in these cities were gathered through a questionnaire survey conducted under the “Prevalence Survey of Important CVDs in China and Research on Key Technologies” project. A total of 13,476 subjects were recruited, and data on hypertension prevalence and the four air pollutants were collected, collated, and analyzed.
Statistical analyses were performed using SPSS software (Version 25.0, IBM Corp., Chicago, IL, USA). General descriptive analysis, chi-squared tests, and multiple linear regression models were employed to explore the impact of air pollutants on blood pressure. The study controlled for variables such as age, sex, ethnicity, marital status, employment status, education level, body mass index (BMI), and location in the basic model. Seasonal factors were added to the final model to account for potential seasonal changes in blood pressure. Multivariate unconditional logistic regression analyses used hypertension as the dependent variable, with covariates including age, gender, marriage, education level, occupation, employment status, ethnicity, region, and BMI. The quartile concentrations of NO2, SO2, PM2.5, and PM10 in cold and warm months were used as independent variables, with the first quartile of each pollutant as the reference value. Trend tests were conducted to calculate the trend of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with changes in pollutant concentration. Graphpad Prism (version 6, GraphPad Software, California, SD, USA) was used to create box charts summarizing pollutant concentrations. Hypertension was defined as either SBP ≥140 mmHg or DBP ≥90 mmHg. Warm months (April to October) and cold months (November to March) were defined based on average monthly temperatures of ≥16°C and <16°C, respectively.
The study included 13,476 residents of Guizhou Province, with a hypertension prevalence rate of 25.9% (3,488/13,476). Significant differences were observed in age, marital status, education level, occupation, employment status, ethnicity, region, and BMI between residents with and without hypertension. The average concentrations of PM2.5, PM10, SO2, and NO2 were 32.65 µg/m3, 59.00 µg/m3, 24.98 µg/m3, and 21.48 µg/m3, respectively, all below the national secondary standard for ambient air quality. Monthly average concentrations of the four pollutants were higher in cold months than in warm months, particularly PM2.5 and PM10, which peaked in December and reached their lowest concentrations in June and July. NO2 and SO2 concentrations were also higher in cold months but exhibited smaller fluctuations throughout the year.
In warm months, the third and fourth quartiles of NO2 were risk factors for elevated SBP, with odds ratio (OR) values of 3.55 (95% confidence interval [CI]: 2.17, 5.80) and 1.94 (95% CI: 1.17, 3.21), respectively. The third quartile of NO2 also increased the risk of elevated DBP, with an OR value of 1.98 (95% CI: 1.04, 3.76). In cold months, the second and third quartiles of NO2 were associated with increased SBP risk, with OR values of 1.51 (95% CI: 1.28, 1.78) and 1.39 (95% CI: 1.21, 1.59), respectively. These quartiles also increased DBP risk, with OR values of 1.30 (95% CI: 1.02, 1.65) and 1.39 (95% CI: 1.14, 1.69), respectively. The second quartile of SO2 was a risk factor for DBP, with an OR value of 1.37 (95% CI: 1.05, 1.76). The second quartile of PM2.5 was associated with increased SBP risk, with an OR value of 1.25 (95% CI: 1.08, 1.43). The fourth quartile of PM2.5 increased DBP risk, with an OR value of 2.09 (95% CI: 1.64, 2.65). Trend tests indicated that changes in PM10 concentrations may impact SBP in Guizhou residents.
Changes in SBP and DBP with increased pollutant concentration (per 10 µg/m3) were analyzed under different multiple linear regression models. PM2.5 and NO2 significantly impacted SBP in the original and final models, while PM10 and SO2 were significant in unadjusted, basic, and final models. For DBP, PM2.5 and SO2 were significant in all three models, while PM10 and NO2 were significant only in the final model.
The study concluded that the prevalence of hypertension among Guizhou residents is 25.9%, with significant differences observed across various demographic factors. Air pollutant concentrations in Guizhou Province are generally low but exhibit higher levels in cold months, likely due to increased coal use for heating. NO2, SO2, PM2.5, and PM10 were found to influence blood pressure, with NO2 and SO2 having the most significant impact in cold months. PM2.5 posed a greater risk for hypertension than PM10. The study confirmed that exposure to air pollutants, even at low concentrations, increases the risk of hypertension. This highlights the importance of controlling air pollutant concentrations to reduce hypertension prevalence among Guizhou residents.
In summary, while Guizhou Province enjoys relatively low air pollutant concentrations, the seasonal variation in pollutant levels significantly impacts blood pressure and hypertension prevalence. Addressing the effects of low concentrations of air pollutants on blood pressure is a critical step toward improving public health in the region.
doi.org/10.1097/CM9.0000000000002949
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