A nested case-control study on association between self-reported occupational sulfur dioxide exposure and hypertension

Background Current evidence on whether occupational sulfur dioxide (SO₂) exposure affects the risk of hypertension is still limited, and the research results of the effect of environmental SO₂ exposure on risk of hypertension remain inconsistent.

Objective To analyze the association between self-reported occupational exposure to SO₂ and the risk of hypertension, and the potential dose-response relationship between the years of exposure to SO₂ and the risk of hypertension.

Methods Based on the Jinchang cohort, a nested case-control study design was adopted. A total of 841 newly diagnosed hypertension patients were followed up as the case group, and the control group was selected with 1∶1 individual matching based on non-occupational factors and occupational factors, respectively. The former matching conditions included age ±2 years old, same gender, working age ±2 years, and home address in the same sub-district. The latter was limited to working in the same workshop on the basis of the former conditions. Finally, the former included 717 controls and the latter included 488 controls. A unified questionnaire was used to collect general demographic characteristics, lifestyle habits, history of diabetes, family history of hypertension, and information on occupational exposure to SO₂ (self-reported history of occupational exposure to SO₂ and years of exposure to SO₂). Conditional logistic regression model was used to analyze the association between occupational exposure to SO₂ and hypertension, and the dose-response relationship between the years of SO₂ exposure and the risk of hypertension.

Results In the nested case-control study matching with the non-occupational factors, the OR of hypertension in workers with self-reported occupational exposure to SO₂ was 2.39 (95%CI: 1.68-3.39); while when matching with the occupational factors, the OR of hypertension in workers with self-reported occupational exposure to SO₂ was 1.48 (95%CI: 1.04-2.12). The results of the dose-response relationship showed that as the SO₂ exposure years increased from 1-9 years, 10-19 years, 20-29 years, and 30 years and above, in the nested case-control study matching with non-occupational factors, the ORs of hypertension were 1.85 (95%CI: 0.68-5.08), 1.46 (95%CI: 0.58-3.67), 1.64 (95%CI: 1.00-2.67), and 4.95 (95%CI: 2.63-9.31), respectively; in the nested case-control study matching with occupational factors, the ORs of hypertension were 0.98 (95%CI: 0.40-2.41), 1.84 (95%CI: 0.72-4.70), 1.37 (95%CI: 0.82-2.29), and 2.44 (95%CI: 1.37-4.35), respectively. The two dose-response relationships were positive by χ² trend test (P_trend<0.05).

Conclusion Self-reported occupational exposure to SO₂ is associated with the risk of hypertension in the study population, and the hypertension risk increases with the increase of SO₂ exposure years.