Loud workplaces are common. The evidence that the noise harms the heart is thin

Hazardous workplace noise is widespread — WHO and ILO estimate that roughly 17% of the general working population is exposed to noise loud enough to count as an occupational hazard [s1]. The more surprising question is whether that noise damages more than hearing, and here the same joint review programme is candid: the evidence that occupational noise causes cardiovascular disease is low-certainty, with a signal for the incidence of heart attacks but little for stroke or high blood pressure [s2]. The classic harm of loud work — noise-induced hearing loss — is not in doubt; the newer claim that the noise reaches the heart is much weaker than it is sometimes stated.

How common the exposure is

The first of the two WHO/ILO reviews set out to estimate how many workers face damaging noise. It pooled 65 studies covering 157,370 participants across 28 countries and all six WHO regions [s1]. Prioritising the four studies that surveyed national probability samples of general working populations, it estimated the pooled prevalence of any high occupational noise exposure — defined as 85 decibels A-weighted (dBA) or above — at 0.17 (95% confidence interval 0.16 to 0.19), from those four studies and 108,256 participants, rated low quality [s1]. That is a little over one worker in six, though the prevalence varied substantially by region, sex, industrial sector, and occupation [s1]. The 85 dBA line matters: it is the level above which noise is treated as an occupational hazard, the threshold both reviews use [s1] [s2].

What the heart-disease review found

The second review asked whether exposure at that level, compared with quieter work below 85 dBA, raises the risk of ischaemic heart disease, stroke, or hypertension [s2]. It pooled 17 studies — 11 cohort and six case-control — comprising 534,688 participants across 11 countries [s2]. The results are a study in how a headline claim dissolves under scrutiny.

The one positive signal was for developing ischaemic heart disease: a relative risk of 1.29 (95% CI 1.15 to 1.43) — but from just two studies and 11,758 participants [s2]. Every other estimate was weaker or null. For dying from ischaemic heart disease, the relative risk was 1.03 (95% CI 0.93 to 1.14) across four studies and nearly 199,000 participants — essentially no effect [s2]. Acquiring a stroke came in at 1.11 (95% CI 0.82 to 1.65), dying from stroke at 1.02 (95% CI 0.93 to 1.12), and developing hypertension at 1.07 (95% CI 0.90 to 1.28) — all with confidence intervals that comfortably include no effect [s2]. The reviewers rated the whole body of evidence very low quality, and stated plainly that they were very uncertain about the effect of occupational noise on each of these outcomes [s2].

Reading the numbers honestly

The temptation is to lead with the 1.29 figure and headline that workplace noise causes heart attacks. The evidence does not support that confidence. A relative risk resting on two studies, set against a null result for the same disease's mortality across a far larger sample, is a hypothesis worth pursuing, not an established fact [s2]. The mechanistic rationale is real — noise is a physiological stressor, and both reviews were commissioned precisely because mechanistic data suggest a plausible pathway from noise to cardiovascular disease [s1] [s2]. But plausibility plus a thin, low-certainty epidemiological signal is exactly the situation where careful language matters, and the reviewers supplied it.

What is and isn't in question

The established harm of occupational noise is hearing — that is not what these reviews were testing, and it is why the 85 dBA hazard threshold exists in the first place [s1]. What the WHO/ILO programme was probing is the additional, contested claim that the same noise burdens the cardiovascular system, and its verdict is a weak, uncertain maybe: a single suggestive estimate for heart-attack incidence, and little else [s2]. For a worker in a loud environment, the durable, evidence-backed reason to protect hearing stands; the case that the noise is also damaging the heart is not yet made. Whether any individual's exposure warrants specific measures is an occupational-health question this article does not answer.