Are Women More Prone To Hypertension Due To Air Pollution?

There is a lot of conversation going around on how women are at significantly higher risk of suffering from hypertension. A recent study published in the journal ‘Epidemiology’ found that of all the people surveyed almost 46% of the people were identified as hypertensive, with high proportions of participants with undiagnosed and untreated hypertension.

It showed an increase of 1µg/m3 in PM2.5 exposure was associated with a four percent increase in hypertension prevalence in women as well as a higher systolic and diastolic blood pressure – an increase of 1.4 mmHg and 0.87 mmHg respectively. In men, the association observed was weaker.

The study surveyed 5,531 adults from 28 peri-urban villages near Hyderabad city. They were all were exposed to fine particulate matter levels above the 10 µg/m³ limit recommended by the World Health Organization (WHO). Average exposure to PM2.5 in this study was 33 µg/m3. The participants were also asked questions around their socio-economic status, lifestyle and household characteristics, including the type of cooking fuel which they generally used (biomass or clean).

It suggests that overexposure to particulate matter leads to a higher prevalence of hypertension, regardless of the type of fuel used for cooking. “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 from urban areas mostly dominated by traffic sources,” study author Ariadna Curto from Barcelona Institute for Global Health (ISGlobal), Spain.

Reason for hypertension

Since the survey was done in a village in Hyderabad, can it be telling of the entire country? We spoke to Delhi Government health Advisor Nimmi Rastogi about the issue of hypertension among women and its higher prevalence in comparison with men, she said,  “Normally there is no gender comparison as such and it is found that women actually have higher chances of low blood pressure than men below the age of 50. But stress is a major precipitator of blood pressure as it leads to oxidative damage to the inner linings of the blood vessels and it could come from diverse places like anxiety, environmental pollution or lack of nutrition. This oxidative stress can manifest hypertension.

The recent study that says that because of exposure to household pollution—suspended particles found to be in higher concentration inside homes which leads to damage in their blood vessels, women are at a higher risk. It is a disturbing trend.”

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Localised fuel choices may impact study result

Care For Air President Jyoti Lavakare noted that the study is very localised and depends on factors specific to Hyderabad leading to the conclusion. “The studies that exist and are validated for years about air pollution triggering hypertension are not gender specific. All persons breathing in air pollution are affected and hypertension is one of the conditions one is exposed to if one is living in extremely polluted places. The study saying that women are more prone to hypertension than men could also be because of local fuel choices of women to cook food.” she specified.

She claimed that the gendered impact of air pollution is not validated by broader studies across all cities. On the impact of fuel used in cooking leading to overexposure to air pollution, Lavkare said, “In India particularly, indoor air pollution as women generally do the cooking where they use biomass, cow dung cakes, etc., they are increasingly prone to all kinds of diseases like hypertension, lung cancer, bronchitis, etc.”

Is there really a gender divide in the contraction of hypertension? 

Bhargav Krishna, senior air pollution scientist and currently at Harvard TH Chan school of Public Health, agreed with Lavakare that while broad studies haven't been done in India yet to show the correct picture of the impact on a particular gender across the country due to air pollution, women living in peri-urban and rural areas exposed to solid fuels are at higher risk of developing respiratory diseases, hypertension, etc.

He cited the following passages from the study, “Women cooking with solid fuels generally have higher Systolic Blood Pressure (SBP) and Diastolic blood pressure (DBP) than clean fuel users. In China, higher levels of ambient PM2.5 were associated with higher SBP in individuals using solid fuels for cooking. However, stratified analysis in women was not sufficiently powered to assess whether the association observed between ambient PM2.5 and SBP may be modified by the cooking fuel used.

The recent study that says that because of exposure to household pollution—suspended particles found to be in higher concentration inside homes which leads to damage in their blood vessels, women are at a higher risk. It is a disturbing trend - Nimmi Rastogi

In the study population, women spend the majority of their time near home (83% of the daytime vs. 57% for men). This suggests that residence-based exposure estimates may be more relevant for women than for men in this setting, and may explain why we observed stronger associations between PM2.5 and BP in women.”

He also noted that assigning exposures based on residences may result in misclassification of exposure for men, potentially leading to lower effect estimates.

While the experts raise some questions with the research claiming women have a higher chance of developing hypertension than men because of air pollution, they also state clearly that air pollution is a huge challenge that we as a country are facing. And while it isn’t fully clear if there are gender-specific details of who is affected more, the cooking gas hugely impacts women negatively and the fact that in the rural belt and urban slums, women don’t take proper care of their health, the disease remains undetected until it reaches a serious stage.

Picture credit- IIASA Blog

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