Systematic Review of 47 Studies Finds Noise and Smoking Are the Most Consistent Risk Factors for Hearing Loss at Work

A new systematic review spanning 47 studies finds hearing loss is widespread across working populations, yet of 89 possible risk factors examined, only noise exposure and previous smoking were consistently linked to hearing damage.

For millions of people, the workplace is the single loudest environment they will ever spend time in. Factories, construction sites, farms, airports, and even busy kitchens expose workers to sound levels that, hour after hour and year after year, can quietly wear down the delicate structures of the inner ear.

Researchers in Malaysia have now pulled together a decade of evidence on just how common hearing problems are among workers, and which factors actually predict who develops them. Their conclusions are both sobering and clarifying: hearing disorders can affect a striking share of some workforces, and among dozens of proposed risk factors, only two showed up consistently across studies.

Background: Why the Researchers Looked at This

Occupational hearing damage comes in several forms, and the terminology matters. Noise-induced hearing loss, often shortened to NIHL, refers specifically to permanent damage caused by loud sound exposure. Hearing impairment describes a measurable reduction in hearing ability, however it arose. A standard threshold shift, or STS, is an early warning sign used in workplace monitoring: a measurable worsening of hearing thresholds compared with a worker's baseline test, often detected before the person notices anything at all.

Despite decades of workplace safety regulation, studies from different countries and industries have reported wildly different rates of these problems, and a long list of possible contributors has accumulated in the literature, from diabetes and smoking to shift patterns and the use of hearing protection devices.

The research team set out to bring order to this scattered evidence. They wanted to know two things: how common each subtype of hearing disorder actually is among workers, and which of the many proposed risk factors hold up consistently when the studies are examined side by side.

How the Study Was Done

The authors searched three major research databases, PubMed, Scopus, and Web of Science, for English-language studies published between 2016 and 2025. To be included, a study had to be conducted in a working population and report either the prevalence of a hearing disorder, the risk factors associated with it, or both.

From each eligible study the reviewers extracted the country, the industrial sector, the subtype of hearing disorder examined, the tools used to assess hearing, the prevalence or incidence estimates, and any risk factors reported. To judge whether a risk factor was consistently supported, they applied van Tulder's criteria, a structured method for grading the strength of evidence across multiple studies, alongside a descriptive analysis of how often each factor appeared.

What the Researchers Found

Forty-seven studies met the inclusion criteria, and the prevalence figures they reported varied enormously. General hearing loss affected anywhere from 3.8 percent to 73.5 percent of workers depending on the study and setting. Noise-induced hearing loss ranged from 0.2 percent to 63.6 percent, and hearing impairment from 2.7 percent to 71.2 percent. The single study reporting standard threshold shift found it in 50 percent of the workers examined.

The review catalogued a remarkable 89 distinct risk factors for hearing disorders, spread across eight domains: medical conditions accounted for 25 factors, work-related characteristics for 18, noise-related factors for 13, lifestyle factors for 12, sociodemographic characteristics for 8, factors related to hearing protection devices for 5, exposure to other occupational hazards for 4, and knowledge-related factors for 4.

Yet when the evidence was weighed for consistency, nearly all of those 89 factors fell away. Only two showed reliable associations with hearing disorders across studies: noise exposure itself, and a history of smoking.

That does not mean the other 87 factors are irrelevant. It means the studies examining them produced conflicting results, used inconsistent definitions, or were too few in number to draw firm conclusions. But it does sharpen the picture of what the evidence currently supports.

What It Means for People with Hearing Loss

For anyone who has spent years working in a loud environment, this review is a reminder that the two most controllable contributors to hearing damage are noise dose and smoking. Consistent use of hearing protection in loud settings, and quitting smoking, remain the interventions with the clearest evidence behind them.

The wide prevalence ranges also carry a practical message: in some industries and settings, hearing problems are not the exception but closer to the norm. Workers who notice difficulty following conversations, especially in background noise, have good reason to get their hearing checked rather than assume the problem is rare or imagined. An early standard threshold shift is by definition detectable before hearing trouble becomes obvious in daily life.

When Noise Has Already Taken a Toll: Help Hearing Speech Through It

Because this review ties workplace hearing damage so firmly to noise, it is worth noting that for people already living with mild to moderate loss, newer FDA-OTC hearing aids are designed around exactly the situation noise-exposed workers describe most: following speech in loud places. Panda Quantum is one such device, a 16-channel receiver-in-canal hearing aid whose adaptive noise reduction is built for clear speech in noisy environments, separating voices from the background rather than simply making everything louder.

Quantum runs 20 hours per charge, and its case carries three additional full charges for 80 hours total, enough for long shifts and commutes between plug-ins. It streams calls, TV, and music over Bluetooth, and an optional companion app can run a frequency-specific hearing test through the aid itself and personalize gain to the user's hearing profile. The app and test are entirely optional, and Quantum works fully out of the box without either. It comes with a 5-year warranty and a 45-day trial that starts when the device arrives.

One caveat worth repeating: FDA-OTC hearing aids are approved for mild to moderate hearing loss. Workers whose loss has progressed to severe or profound levels will still benefit most from a clinical fitting with an audiologist.

Limitations of This Research

A systematic review is only as uniform as the studies it summarizes, and here the underlying studies differed widely in how they defined hearing disorders, which assessment tools they used, and which industries they sampled. That heterogeneity is the most likely explanation for prevalence ranges as wide as 3.8 to 73.5 percent, and it means the pooled picture should be read as a map of the evidence rather than a single global estimate.

The review was also restricted to English-language studies published from 2016 onward, so relevant findings in other languages or from earlier years were not captured. And the fact that only two risk factors met the consistency bar reflects the state of the literature as much as biology: many of the other 87 factors simply have not been studied often enough, or uniformly enough, to judge.

Where This Leaves Us

Ten years of research on working populations points to a clear, almost old-fashioned conclusion: protect your ears from noise and do not smoke. Everything else on the long list of proposed risk factors awaits better and more consistent evidence. For workers who suspect the damage is already done, the sensible next step is a hearing check, because the earlier a change is caught, the more options remain open.

Ismail MF, Yew SQ, Ooi ZQ, Yusoff HM. Prevalence and risk factors of hearing disorders among working populations - A systematic review. American Journal of Otolaryngology. 2026. Retrieved from PubMed. https://doi.org/10.1016/j.amjoto.2026.104927