Exposure to airborne fine particulate matter may elevate BP, risk for hypertension
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Researchers in India reported significant associations between exposure to air pollution and high systolic BP and incident hypertension in urban Delhi.
For the substudy of the COE-CARRS study published in Hypertension, investigators evaluated the effects of long- and short-term exposure to airborne fine particulate matter of diameter less than 2.5 m (PM2.5) on longitudinally measured systolic and diastolic BP and incident hypertension among 5,342 Delhi residents.
“The existing evidence for effects of air pollution on health mainly originates from countries with low pollution levels. This study shows the effects of air pollution at some of the highest global levels in a large population,” Dorairaj Prabhakaran, MD, DM, MSc, executive director at the Centre for Chronic Disease Control in New Delhi, told Healio. “The novelty of the detailed exposure assessment makes it possible for us to retrospectively assess exposure for multiple years both in short and long term. The longitudinal nature of the study presents evidence that is robust and fills a gap that existing cross-sectional studies cannot. Finally, the findings have serious policy implications by which we see an approximate reduction of 15% in hypertension prevalence given the attainment of national standards in Delhi.”
The analysis utilized baseline and two follow-up measurements of participant BP (50% women; mean age, 44 years).
Investigators utilized a satellite-based hybrid exposure model to measure daily airborne PM2.5 concentrations at 1×1 km in Delhi from 2010 to 2016.
At baseline, average exposure to airborne PM2.5 at baseline was 92.1 g/m3 annually and 82.4 g/m3 monthly. These averages increased to 121.7 g/m3 annually and 93.4 g/m3 monthly by the time of the last follow-up BP measurements.
Researchers observed an average increase of 1.77 mm Hg (95% CI, 0.97-2.56) for systolic BP and 1.17 mm Hg (95% CI, 0.65-1.7) for diastolic BP for each interquartile range increase in monthly PM2.5 exposure. They also observed an average systolic BP increase of 3.33 mm Hg (95% CI, 1.12-5.52) BP for each interquartile range increase in annual PM2.5 exposure. The annual effects of airborne pollution on diastolic BP were not statistically significant.
According to the study, for each interquartile range difference in exposures at 1 year, 1.5 years and 2 years, the risk for incident hypertension was elevated as follows:
- at 1 year of exposure (HR = 1.53; 95% CI, 1.19-1.96);
- at 1.5 years of exposure (HR = 1.59; 95% CI, 1.31-1.92); and
- at 2 years of exposure (HR = 1.16; 95% CI, 0.95-1.43).
Moreover, among individuals with similar levels of PM2.5 exposure, those with waist-to-hip ratios of more than 0.95 experienced greater risk for hypertension compared with those with smaller ratios :
- at 1 year of exposure (HR = 1.89; 95% CI, 1.35-2.65);
- at 1.5 years of exposure (HR = 1.62; 95% CI, 1.23-2.14); and
- at 2 years of exposure (HR = 1.27; 95% CI, 0.97-1.65).
“The study was limited to Delhi, although we are currently carrying out a similar analysis for Chennai, a city in southern India,” Prabhakaran said in an interview. “We need to carry out the exposure assessment across the nation and leverage existing longitudinal cardiovascular cohorts to accurately study the dose response, which might be varying significantly from region to region.”
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