Association Between Tea Consumption And Blood Pressure In Chinese Adults

BackgroundHypertension is a clinical syndrome characterized by raised systemic arterial blood pressure(BP).Persistent hypertension will lead to a series of complications,seriously affecting health and quality of life,Previous study have demonstrated that elevated BP is one of the major contributors to the global disease burden.It is predicted that the numbers of people affected by hypertension will rise in all regions of the world from 2000 to 2025,especially in developing countries.A recent investigation from China showed that 23.2%(about 244.5 million)of the Chinese adults were diagnosed with hypertension.The prevalence of hypertension is increasing without effective control in China.In view of the seriousness of harm and the difficulty to control,preventing elevated BP becomes more important.Tea culture has a long history in China,and tea has become a popular beverage all over the world which is consumed only second to water.Even if the effect of tea consumption on the individual is weak,the public health implication is enormous.Tea contains complex compositions,such as proteins,carbohydrates,minerals and trace elements,polyphenols,alkaloids,amino acid and so on.Although mounting evidences showed that polyphenols can make an important contribution to vascular health,the effect of tea consumption on BP was not clear,and little was known about the dose-response relationship.Evidences from animal experiments have demonstrated that tea lowered BP in mice.Furthermore,several epidemiological studies in different countries and populations supported the claim that drinking tea can reduce BP.But the lack of a statistical correlation has been documented in other studies.Few studies have reported contrary conclusions.At present,there is no recommended dose for tea intake,and most previous studies have used linear model to analyze without judgment basis.In this study,the non-linear detection problem was considered,and further stratified analysis was conducted to explore the relationship between tea consumption and BP in different subgroups.Objectives1.To explore the association between tea consumption and systolic blood pressure(SBP)and diastolic blood pressure(DBP)in Chinese adults.2.To compare the association between tea consumption and SBP and DBP in different subgroups.MethodsThe data derived from China Health and Nutrition Survey(CHNS),an international collaborative project conducted by the National Institute for Nutrition and Health(NINH)of the Chinese Center for Disease Control and Prevention(CCDC)and University of North Carolina at Chapel Hill(UNC).It is an ongoing dynamic cohort established in 1989 and updated in 1989,1991,1993,1997,2000,2004,2006,2009,2011 and 2015.The independent and dependent variables used in this study appeared in 7 surveys conducted between 1993 and 2011.Because of repeated measurements of samples was less,to avoid the waste of data and possible selection bias,we formed a data by including both the information of participants who were not measured repeatedly and the baseline information of participants who were measured repeatedly.And we put dummy variables generated by the survey year into the model for adjustment to control the influence of survey time.According to the inclusion and exclusion criteria,17965 subjects were retained in this study.The tea consumption and blood pressure were treated as continuous variables.First,the restricted cubic spline was used to judge whether there was a non-linear relationship and draw non-linear curves.Second,piecewise linear regression was used to find the threshold in the non-linear relationship and multiple linear regression was performed for the possible linear relationship.Results1.The results of restrictive cubic spline analysis showed that there were non-linear relationships between tea consumption and SBP(β2=1.03,P<0.01)and DBP(β2=0.51,P<0.01)after adjusting for various confounding factors in general population.The non-linear relationships were nearly J-shaped curve.Stepwise regression results showed that thresholds of tea consumption for SBP and DBP were 3 cup/day(720ml/day).2.Results of subgroup analysis showed that there was still a non-linear relationship between tea consumption and SBP(β2=1.41,P<0.01),but no non-linear relationship was found between tea consumption and DBP(β2=0.37,P=0.15)in non-hypertensive male population.The non-linear relationship was also nearly J-shaped curve.Stepwise regression results showed that threshold of tea consumption for SBP was 3 cup/day(720ml/day).Linear regression results showed no statistical association between tea consumption and DBP(β=0.03,P=0.53).However,non-linear relationships between tea consumption and SBP(/32=0.13,P=0.62)and DBP(β2=-0.10,P=0.60)were not found in the non-hypertensive female population.Multiple linear regression showed that no statistical associations between tea consumption and SBP(β=-0.01,P=0.89)and DBP(β=-0.02,P=0.78).We found a non-linear relationship between tea consumption and SBP(β2=1.70,P=0.02),but no non-linear relationship between tea consumption and DBP(β2=0.39,P=0.36)in hypertensive males.The non-linear relationship was also nearly J-shaped curve.Stepwise regression results showed that threshold of tea consumption for SBP was 5 cup/day(1200ml/day).Linear regression results showed no statistical association between tea consumption and DBP(β=-0.08,P=0.57).In hypertensive women,no non-linear relationship was found between tea consumption and SBP(β2-1.40,P=0.16)and DBP(β2=0.72,P=0.16).Linear regression analysis also found no statistical association between tea consumption and SBP(β=0.60,P=0.06)and DBP(β=0.23,P=0.31).ConclusionsThe present study found that there was a nearly J-shaped relationship between tea consumption and SBP and DBP,and thresholds of tea consumption were about 3 cup/day(720ml/day).But the amount of tea consumed should be treated differently for different subgroups.More longitudinal and basic medical research is needed to confirm the relationship and reveal the underlying mechanisms.