A recent study investigated the relationship between occupational noise-induced hearing loss and blood pressure. The authors conclude that chronic noise exposure increases the risk of hypertension.

According to the new paper, globally, more than 600 million people have jobs that expose them to hazardous noise levels.

This high number makes noise exposure one of the most common workplace hazards.

In line with this, occupational noise-induced hearing loss is the most prevalent job-related condition in the United States.

Over recent years, scientists have shown that noise exposure does not only affect hearing.

For instance, studies have concluded that exposure to noise might negatively influence cardiovascular health and even digestive health.

The authors of the recent study, which features in PLOS ONE, decided to focus on its effect on hypertension.

Noise exposure and blood pressure

Currently, more than 100 million adults in the United States have high blood pressure. For this reason alone, it is important to understand any factors that might increase risk.

Earlier studies have investigated links between noise exposure and hypertension, but so far, the findings have been inconsistent. The authors of the current study believe that this is partly because it is difficult to quantify total noise exposure over decades.

To address this issue, the researchers used hearing loss as a marker for noise exposure. The authors explain:

"Several studies [have] reported that bilateral high frequency hearing loss (BHFHL) is associated with cumulative occupational noise exposure, and BHFHL can serve as an early biomarker for the actual personal exposure to occupational noise."

The scientists had access to data from 21,403 workers with occupational noise exposure and an average age of 40 years. This information came from a survey of workers in Chengdu, Sichuan Province, in China.

As part of the survey, the officials assessed various health metrics, using audiometric tests and measuring blood pressure.

A significant association

As expected, the prevalence of hearing loss increased in tandem with the number of years that the participants had spent working with occupational noise exposure.

Overall, the researchers found that workers with "mild and high BHFHL had [an increased] hypertension risk of 34% and 281%, respectively." The authors conclude:

"The present study suggested that occupational noise exposure was positively associated with blood pressure levels and hypertension risk."

They also report that a "dose-response relationship between BHFHL and hypertension was found in both males and females."

In this study, the authors found that the link between noise exposure and hypertension was most pronounced in men. They believe that this might be because "[m]ale workers [are] usually exposed to higher noise intensity in their workplace, compared with female workers."

Strengths and limitations

This study's large sample size lends weight to the findings. Similarly, the scientists used both BHFHL and duration of work to assess noise exposure. The authors believe that this tandem approach might "strengthen the effectiveness and credibility of the results by mutual confirmation."

However, there are certain shortfalls. Firstly, as the authors recognize, because the study is cross-sectional—meaning that the team did not track the participants over the years—it is not possible to prove cause and effect.

Also, the authors note that their analysis could not account for some variables that affect hypertension risk. These include BMI, smoking status, alcohol intake, and psychological factors.

In addition, the researchers did not visit workplaces to assess actual noise levels, and they did not have any information on whether the participants used ear defenders.

Although this study concludes that noise exposure affects blood pressure, other studies have not found the same relationship. Despite this study's size, scientists will need to carry out more work before noise exposure becomes an official risk factor for hypertension.

—Tim Newman