| BackgroundCardiovascular Disease is a critical harmful disease to public health.Increased of low-density lipoprotein cholesterol(LDL-C)have confirmed to be one of the most significant risk factors of cardiovascular disease.Other dyslipidemia,such as decreased of high-density lipoprotein cholesterol(HDL-C)or increased of triglyceride(TG)can also increase the risk of coronary heart disease and stroke.Tea is the most common beverage except water.The possible protective effects on cardiovascular disease may due to polyphenolic antioxidants in tea.Epidemiological studies have shown that drinking tea or taking tea extract can reduce the risk of cardiovascular disease.The mechanism may be polyphenols in tea which can improve vascular endothelial function,reduce blood pressure,anti-oxidation,improve cholesterol metabolism.Systematic review and meta-analysis of randomized controlled trials showed that taking green tea,black tea or their extract can reduce total cholesterol(TC)and LDL-C in human.However,since randomized controlled trials were restricted in duration,the dose of tea intake,participants and samples,can not represent the natural population accurately.At present,there were few observational studies on the association between tea and blood lipids in natural populations.There were few studies on Chinese population either.The aim of our study was to explore the relationship between drinking tea and blood lipid in middle-aged and aged population in China.ObjectiveThe study is to explore association of drinking tea with blood lipids levels in middle-aged and aged population in China.MethodsThe data came from once review of a cohort,which conducted in 2007 and 2008.The cohort was built in 1998(China Multi-center study of Cardiovascular Epidemiology).The cohort used cluster random sampling,in different regions,different types of people in the extraction of 15 groups of samples,aged 35 to 59 years and each sample about 1,000 people.From 2007 to 2008,11 out of 15 groups were recruited to review.We recruited 8,409 people and review rate was 73%.1,012 people with incomplete data,170 people with history of stroke,coronary heart disease,malignant tumor or end-stage renal disease were excluded,and the remained 7,227 participants(3,304 male and 3,923 female)included in the analysis.The data of drinking tea,demographic characteristics,smoking,drinking,red meat intake,intensity of physical activity,exercise intensity,medication history were collected by unified questionnaire.Blood samples were collected,processed,transported and stored by unified method.Regular drinking tea means drinking tea at least 3 times a week and continuous drinking tea continued more than 6 months.The species of tea includes non-fermented tea(green tea),fermented tea(black tea,Pu’er tea,Tikuanyin tea and oolong tea),other tea(scented tea and other tea species).The amount of drinking tea includes frequencies of making tea by participants per day and grams of tea were consumed by participants per month.The association between tea and blood lipids in middle-aged and aged population were assessed by covariance analysis after adjusted sex,age,urban and rural,educational level,north and south,smoking,drinking,waist circumference,red meat intake,working strength labor intensity,exercise intensity,history of hypertension,history of diabetes mellitus,history of hypercholesterolemia.Association of amount tea with blood lipids in middle-aged and aged population were assessed by multiple linear regression model.Results1.Baseline information.A total of 7227 participants(3304 males and 3923 females.2649 urban residents and 4578 rural residents.2962 northern residents and 4265 southern residents.4964 non-central obese participants and 2263 central obese participants)were analyzed in our study.The mean age was 55.60±7.12 years.Characteristics of drinking tea:The rate of regular drinking tea in all participants was 41.68%.In the regular tea drinkers,the ratio of intake non-fermented tea,fermented tea and other tea were 50.53%,24.77%,24.70%,respectively.In the regular tea drinkers,the ratio of making tea once a day and twice a day were 68.89%,31.11%,respectively.In the regular tea drinkers,the ratio of drinking 50 to 249g tea per month,250 to 499g tea per month and 500g or more tea per month were 53.32%,30.48%,16.20%,respectively.Blood lipid level:The average level of TC was 4.97±0.97mmol/L,LDL-C was 2.83±0.84 mmol/L,HDL-C was 1.42±0.37 mmol/L,TG was 1.41± 1.74 mmol/L and non-HDL-C was 3.55±0.96 mmol/L in the total participants.Compared with male and female,the levels of TC,LDL-C,HDL-C and non-HDL-C were lower and TG was higher in male(P<0.05).Basic information of each groups of tea drinking situations.There were statistical differences in the basic information between the two groups(non-regular drinking tea group,regular drinking tea group),except taked lipid-lowering drugs in the last two weeks in the total participants.There were statistical differences in the basic information between the four groups(non-regular drinking tea group,the non-fermented tea group,the fermented tea group and the other tea group),except taked lipid-lowering drugs in the last two weeks in the total participants.There were statistical differences in the basic information between the three groups(non-regular drinking tea group,consumption of one time per day group,consumption of more than one time per day group),except taked lipid-lowering drugs in the last two weeks in the total participants.There were statistical differences in the basic information between the four groups(non-regular drinking tea group,consumption of ≥50,<250 grams per month group,consumption of ≥250,<500 grams per month group,consumption of ≥500 grams per month group),except taked lipid-lowering drugs in the last two weeks in the total participants.2.The association of tea drinking with blood lipids.2.1 The association of regular drinking tea with blood lipidsAccording to the frequency of drinking tea,all the participants were divided into two groups.Single factor analysis showed,compared with non-regular drinking tea group,the TC,non-HDL-C and TG were higher in regular drinking tea group(P<0.05)There was no significant difference in HDL-C and LDL-C between the two groups(P>0.05).Multivariate covariance analysis showed that serum LDL-C(difference:-0.07mmol/L,P<0.05)and non-HDL-C(difference:-0.05mmol/L,P<0.05)were lower,HDL-C(difference:0.04mmol/L,P<0.05)and TG(difference:0.07mmol/L,P<0.05)were higher in the regular drinking tea group.2.2 The association of categories of regular drinking tea with blood lipidsAccording to the categories of regular drinking tea,all the participants were divided into 4 groups.Multivariate covariance analysis showed,compared with the non-regular drinking tea group,LDL-C was lower(difference:-0.08 mmol/L,P<0.008;difference:-0.11 mmol/L,P<0.008),HDL-C were higher(difference:0.03mmol/L,P<0.008;difference:0.06mmol/L,P<0.008),TG were higher(difference:0.10mmol/L,P<0.008;difference:0.10mmol/L,P =0.0081)in the non-fermented tea group and the fermented tea group.2.3 The association of tea amount with blood lipidsIn the multiple linear regression model,LDL-C had a negative correlation with frequencies of making tea per day(β=-0.042,P for trend<0.05),and HDL-C,TG had a positive correlation with frequencies of making tea per day(β=0.026,P for trend<0.05;β=0.016,P for trend<0.05).In the multiple linear regression model,LDL-C had a negative association with tea consumption per month(β=-0.031,P for trend<0.05),and HDL-C,TG had a positive association with tea consumption per month(β=0.025,P for trend<0.05;β=0.012,P for trend<0.05).Conclusion1.Association of regular drinking tea with serum TC is not consistent in different populations2.Serum LDL-C had a negative association with regular drinking tea.The association was consistent in total,male,rural,southern,non-central obese participants.3.Serum HDL-C had a postive association with regular drinking tea.The association was consistent in other participants except male participants.4.Serum non-HDL-C had a negative association with regular drinking tea.The association was consistent in total,rural,southern,non-central obese participants.5.Serum HDL-C had a postive association with regular drinking tea.The association was consistent in total,male,non-central obese participants.6.The non-fermented tea and fermented tea was negative association with serum LDL-C,which was postive association with HDL-C and TG levels in the total participants.7.Serum LDL-C had a negative,HDL-C and TG had a positive association with times of making tea per day and tea consumption per month.The above associations are independent from possible influencing factors.The impact of long term regular tea drinking on blood lipids and lipoprotein levels should be confirmed by further prospective studies. |
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