Risk factors for prehypertension and their interactive effect: a cross- sectional survey in China.

Background: Individuals with prehypertension are at higher risk of developing hypertension and cardiovascular diseases, while the interaction between factors may aggravate prehypertension risk. Therefore, this study aimed to evaluate the risk factors for prehypertension in Chinese middle-aged and elderly adults, and explore the potentially interactive effect of evaluated factors.

Methods: All the participants that came from a community based cross-sectional survey were investigated in Bengbu, China, by being interviewed with a questionnaire. Body mass index (BMI), Waist circumference (WC) and lipid accumulation product (LAP) that reflect participants' obesity were also calculated. In addition, logistic regression model was applied to explore the risk factors of prehypertension, followed by the assessment of the interactive effects between risk factors on prehypertension by the relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP) and synergy index (SI).

Results: A total of 1777 participants were enrolled in this study, among which the prevalence of normtension, prehypertension and hypertension were 41.70%, 33.93% and 24.37% respectively. According to the multivariate logistic regression analysis, age (OR: 1.01, 95%CI: 1.00-1.02), smoking (OR: 1.67, 95%CI: 1.22-2.29), family history of cardiovascular diseases (OR: 1.52, 95%CI: 1.14-2.02), general obesity (OR: 1.51, 95%CI: 1.15-1.97) and LAP (OR: 2.58, 95%CI: 1.76-3.80) were all defined as the major factors that significantly related with the risk of prehypertension. When identifying prehypertension risk, the receiver-operating characteristics (ROC) curves (AUC) analysis indicated that LAP performed better than BMI in males (Z = 2.05, P = 0.03) and females (Z = 2.12, P = 0.03), but was superior to WC only in females (Z = 2.43, P = 0.01). What is more, there were significant interactive effects of LAP with family history of cardiovascular diseases (RERI: 1.88, 95%CI: 0.25-3.51; AP: 0.44, 95%CI: 0.20-0.69; SI: 2.37, 95%CI: 1.22-4.60) and smoking (RERI: 1.99, 95%CI: 0.04-3.93; AP: 0.42, 95%CI: 0.17-0.67; SI: 2.16, 95%CI: 1.68-4.00) on prehypertension risk. The value of AP (0.40, 95%CI: 0.03-0.77) also indicated a significant interaction between family history of cardiovascular diseases and smoking on prehypertension.

Conclusion: Prehypertension is currently prevalent in Chinese adults. This study indicated that age, family history of cardiovascular diseases, smoking, general obesity and LAP were significantly related with prehypertension risk. Furthermore, interactive effects on risk of prehypertension had been demonstrated in this study as well, which would help researchers to build strategy against prehypertension more comprehensively and scientifically.