Objectives: Previous studies on the effects of angiotensinogen (AGT) gene polymorphisms and chronic exposure to occupational noise on the risk of hypertension have mainly been cross-sectional or prevalent case-control studies, where temporality constitutes problems. The present study was to assess longitudinally both independent and joint effects of AGT gene polymorphisms and chronic exposure to occupational noise on occurrence of hypertension.
Methods: The authors conducted a 20-year prospective cohort study of 1301 aviation workers in Taiwan. The study population included 912 workers without hypertension at baseline. The outcome of interest was the development of hypertension during the study period. The studied determinants were three AGT genotypes (TT, TM and MM) and four exposure categories according to the levels of noise representing high (>80 dBA), medium (80-65 dBA), low exposure (64-50 dBA) and the reference level (49-40 dBA).
Results: In Poisson regression adjusting for confounders, AGT (TT vs MM adjusted incidence rate ratio (IRR) 1.77, 95% CI 1.24 to 2.51) and noise exposure (high and medium combined) during 3-15 years (adjusted IRR 2.35, 95% CI 1.42 to 3.88) were independent determinants of hypertension. Furthermore, the risk of hypertension increased with noise exposure (adjusted IRR 3.73, 95% CI 1.84 to 7.56) among TT homozygotes but not among those with at least one M allele (Rothman synergy index=1.05).
Conclusions: The results evidence further the independent effects of AGT gene polymorphisms and exposure to occupational noise. Our finding also suggests that workers carrying TT variant allele have higher risk of hypertension under chronic exposure to occupational noise.