Noise Exposure Leads to Hyperglycemia

Aug 15, 2020 Editor: Steve Freed, R.PH., CDE
Author: Sameen Khan, Pharm.D. Candidate, USF College of Pharmacy 

Stress hormones triggered by noise exposure affect insulin secretion and sensitivity, leading to increased hyperglycemia risk. 

Studies have reported an association between exposure to high noise levels and the activation of stress hormones such as cortisol, which reduces pancreatic insulin secretion and decreases insulin sensitivity throughout the body, leading to increased risk of developing type 2 diabetes. This association is alarming for those with occupations that cause high levels of loud noise exposure regularly. Concerns have been validated by researchers; for example, in a 2011 cross-sectional study, which linked noise-induced hearing loss with impaired fasting glucose levels. Also, the 2014 U.S. national survey associated elevated body mass indexes (BMI) with patients that self-reported occupational noise exposure.

A 2012 retrospective cohort study investigated the incidence of hyperglycemia in machinery and equipment manufacturing workers exposed to increased noise levels over one year. Researchers recruited study participants from four job sites, excluding those with a history of diabetes or who were unable to follow up with researchers after one year, culminating in 905 total study participants. A health examination was performed at the commencement of the study, which required that participants undergo an overnight fast so that baseline fasting plasma glucose levels could be determined. Noise exposure levels were determined through a walkthrough survey that utilized a personal noise dosimeter to report sound levels in decibels from the working hours of 08:00 to 17:00, excluding 12:00 to 13:00. An eight-hour time-weighted average (TWA) was then calculated. Participants were then classified into “high” (≥ 85 decibels), “medium” (70-85 decibels), and “low” (<70 decibels) exposure groups. The study’s primary endpoints were diagnosis of prediabetes, initiation of hypoglycemic medication, or end of the one-year study period.

Demographics between the exposure groups varied considerably. Those in high occupational noise exposure jobs were mostly male and had lower educational levels than those in the low-exposure groups. Only 23.25% of those in the high exposure group had an education level of greater than 12 years, while 82.4% of those in the low exposure group did.  Smoking was more common as sound exposure increased. The high-exposure group had the highest incidence of smoking and reported 38.9% as smokers, the medium-exposure group had 28.6% smokers, and of the low-exposure group, only 15.9% were smokers. Statistical analysis utilizing the Cox proportional hazard regression model found that participants exposed to high levels of noise defined in the study as ≥ 85 decibels were at significantly higher risk of developing hyperglycemia than their low (<70 decibels) noise exposure counterparts. The high exposure group had a 1.80 risk ratio for developing hyperglycemia, reported with a 95% confidence interval (1.04-3.10) compared to the low exposure group.  

Awareness that high levels of noise exposure are a risk factor for hyperglycemia is an essential step in combatting it, particularly for those for whom it is unavoidable due to it being a byproduct of their occupation. Hearing-protective devices are critical in reducing the risk of developing hyperglycemia, which could lead to a chronic condition such as type 2 diabetes. This study‘s greatest strength was in the retrospective cohort design, which provided information based on a longitudinal follow-up of workers exposed to various noise levels. However, it did have limited knowledge of noise exposure that workers may have had outside of work, and was limited to one year. Additionally, researchers only measured the pre-prandial blood glucose levels. They did not measure postprandial levels, and these levels were only taken at the beginning and end of the study. The study would have benefited by having more measurements to correlate noise exposure to blood glucose levels strongly. For this reason, researchers recommend using animal models to study the impact of noise on hyperglycemia further. 

Practice Pearls: 

• Noise levels greater than or equal to 85 decibels are highly correlated with an increased incidence of hyperglycemia. 
• Those in jobs with high noise level exposure are likely to be males, smokers, and have a lower education status than those in jobs with reduced noise exposure. 
• Hearing protective devices may be used to help protect against the development of diabetes. 

Chang, Ta-Yuan, et al. “Occupational Noise Exposure and Its Association with Incident Hyperglycemia Retrospective Cohort Study.“ Nature, 22 May 2020, doi:10.2139/ssrn.3284860. 

Sameen Khan, Pharm.D. Candidate, USF College of Pharmacy