BACKGROUNDIncreased blood pressure and elevated total cholesterol (TC) level are the two most important modifiable risk factors of cardiovascular disease (CVD) in the world. Hypertension and hypercholesterolemia co-exist more often than would be expected and whether there is a synergistic impact on fatal CVD between elevated TC and hypertension need to be further examined in Chinese population.

METHODSWe conducted a cohort study which recruited 5092 Chinese male steelworkers aged 18 - 74 years in 1974 - 1980 and followed up for an average of 20.84 years. Totally 302 fatal CVD events were documented by the year of 2001. Cox proportional hazards regression models were undertaken to adjust for baseline variables with fatal CVD events as the outcome variable. Additive interaction model was used to evaluate the interaction between elevated TC and hypertension.

RESULTSHypercholesterolemia and hypertension were significantly associated with an increased hazard ratio (HR) of fatal CVD (1.67 (95%CI 1.18 - 2.38) and 2.91 (95%CI 2.23 - 3.80) respectively. Compared to participants with normotension and TC < 240 mg/dl, the HRs were 1.11 (95%CI 0.56 - 2.21), 2.74 (95%CI 2.07 - 3.64) for hypercholesterolemia and hypertension respectively, and 5.51 (95%CI 3.58 - 8.46) for participants with both risk factors. There was an additive interaction with a 2.65 (95%CI 0.45 - 4.85) relative excess risk (RERI) between hypercholesterolemia and hypertension on CVD.

CONCLUSIONWe found that the risk of fatal CVD was significantly associated with an additive interaction due to hypercholesterolemia and hypertension besides a conventional main effect derived from either of them, which highlights that the prevention and treatment of both risk factors might improve the individual risk profile thus reduce the CVD mortality.