Hypertension on the rise in Indian women due to air pollution

London: Exposure to higher levels of indoor air pollution in India is associated with an increased risk of hypertension among women, according to a study.

Researchers led by the Barcelona Institute for Global Health (ISGlobal) in Spain studied the association in India, where burdens of air pollution and hypertension are projected to increase. The results show that women exposed to higher levels of air pollution at home have a higher hypertension prevalence.

The study, published in the journal Epidemiology, studied 5,531 adults from 28 peri-urban villages near Hyderabad city. The researchers measured systolic and diastolic blood pressure of participants and estimated their annual residential exposure to fine particulate matter (PM2.5) and black carbon. The participants also answered a survey to determine socio-economic status, lifestyle and household characteristics, including the type of cooking fuel generally used.

All study participants were exposed to fine particulate matter levels above the 10 microgrammes per cubic metre limit recommended by the World Health Organization (WHO). Average exposure to PM2.5 in this study was 33 microgrammes per cubic metre. Based on the blood pressure measurements, almost half of participants (46 per cent) were identified as hypertensive, with high proportions of participants with undiagnosed and untreated hypertension.

The results show that an increase of one microgramme per cubic metre in PM2.5 exposure was associated with a four per cent increase in hypertension prevalence in women, as well as a higher systolic and diastolic blood pressure – an increase of 1,4 millimetres of mercury (mmHg) and 0.87 mmHg, respectively. In men, the association observed was weaker, researchers said. "Women spend most of their time near their households in this study area – 83 per cent of their daily time as compared to 57 per cent for men, which could explain why we observe a stronger association in women than in men," said Ariadna Curto, first author of the study.

The study indicates that long-term exposure to particulate matter is associated with a higher prevalence of hypertension, regardless of the type of fuel used for cooking. "Other studies have found that women that cook with solid fuels such as biomass tend to have higher blood pressure than those using clean fuels, although our data is not powered enough to support this," Curto said. "Our study suggests that the effects of outdoor air pollution on cardiovascular health may be independent from those of indoor air pollution," she said.

"In the light of our lack of association with black carbon, it is important to keep in mind that this is a peri-urban area, where the sources and chemical makeup of air pollution differ to urban areas mostly dominated by traffic sources," Curto said. Cathryn Tonne, the study coordinator, said that the mechanisms by which air pollution could contribute to high blood pressure "include inflammation and oxidative stress, which may lead to changes in arterial function."

"Although further epidemiological evidence is needed to confirm our findings, ideally through longitudinal studies, these data suggest that public policies aimed at reducing air pollution will greatly benefit cardiovascular health," said Tonne.