Body mass index modifies the noise-hypertension link: a cross-sectional study in automobile workers

Background Occupational noise is a pervasive occupational hazard. While it is a well-established cause of hearing loss, only a few studies have suggested a potential association with cardiovascular diseases, and the evidence remains limited. Furthermore, individual susceptibility varies substantially, and metabolic characteristics, such as body mass index (BMI), may play a modifying role. Objective To systematically examine the effect of BMI modification on occupational noise exposure duration and hypertension risk. Methods A cross-sectional study was conducted among workers at an automobile manufacturing plant. Demographics, occupational history, and medical examinations were collected. Modified Poisson regression models were used to estimate prevalence ratios (PRs). The modifying effect of continuous BMI was evaluated by incorporating an interaction term, with a sensitivity analysis performed using binary BMI classifications. Johnson-Neyman technique was used to determine the point at which the association was no longer statistically significant. Results There were 21.6% of participants with hypertension in this plant. Occupational noise exposure duration was positively associated with the risk of hypertension. The continuous BMI showed a significant negative interaction with noise exposure duration (PR = 0.987, 95% CI [0.979–0.995], P = 0.001). Specifically, at a BMI of 18.5 kg/m 2 , each additional year of noise exposure duration increased hypertension risk by 11.9% (PR = 1.119, 95% CI [1.047–1.196]); at a BMI of 24.0 kg/m 2 , this association was attenuated but remained significant (PR = 1.041, 95% CI [1.008–1.075]); and at a BMI of 28.0 kg/m 2 , no significant association was observed (PR = 0.987, 95% CI [0.956–1.019]). With Johnson–Neyman, the BMI value above which the estimated association was no longer statistically significant was identified at 27.02 kg/m 2 . In sensitivity analysis, treating BMI as a binary variable, the association between noise exposure duration and hypertension risk was attenuated and no longer statistically significant in overweight/obese individuals but remained significant in normal-weight individuals, and the negative interaction between noise exposure duration and BMI remained statistically significant (PR = 0.919, 95% CI [0.863–0.979], P = 0.010). Conclusions The association between occupational noise exposure duration and hypertension risk was modified by BMI in this cross-sectional study of automobile manufacturing workers. The association was more pronounced among normal-weight workers, whereas it was attenuated and no longer statistically significant at higher BMI levels. These findings suggest that BMI may be an important consideration in occupational health surveillance and hypertension risk assessment among noise-exposed workers, warranting further longitudinal investigation.