Occupational exposure to noise and the cardiovascular system: a meta-analysis

The aim of our meta-analysis is to evaluate the association between the modifications of the cardiovascular system and chronic exposure to noise in occupationally exposed subjects. We considered the articles published from 1950 to May 2008. Only 15 papers were conforming to the inclusion criteria identified for this meta-analysis. A total of 18,658 workers were divided in three groups according to the level of noise exposure as measured in the original studies (High Exposure, HE, Intermediate Exposure, IE, Low Exposure, LE). A preliminary evaluation of the type of data allowed for a classification of the type of performed measurements. Two classes of variables were identified: Class I, composed by continuous variables (systolic blood pressure, SBP, diastolic blood pressure, DBP, and heart rate, HR) and Class II, composed by not continuous variables (prevalence of hypertension and prevalence of ECG abnormalities). For each variable the calculation of heterogeneity was performed. For continuous variables the calculation of ES and its significance were performed while Odds Ratio (OR) and its significance were calculated for not continuous variables. The results show a statistically significant increase of SBP and DBP in HE workers compared to LE and IE workers while HR is statistically higher in HE participants compared to LE participants. The prevalence of both hypertension and ECG abnormalities is statistically higher in HE workers compared to LE and IE workers. Taking into account both the extremely high heterogeneity among studies and the ES/OR values we suggest a particular attention to the measurement and evaluation of SBP, DBP and HR in workers with chronic exposure to noise. Also ECG for workers with chronic exposure to noise is suggested in order to identify and evaluate possible abnormalities noise could be a concurrent cause of.