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The Relationship of Obesity and Atrial Fibrillation among Chinese Populations

Author: ZhangXing
Tutor: WuYangFeng
School: Peking Union Medical College , China
Course: Epidemiology and Biostatistics,
Keywords: Non - valvular atrial fibrillation Prevalence Investigation of Risk Factors In the elderly population Continuous variables Medical large Echocardiography Cardiovascular disease Male Female
CLC: R541.7
Type: Master's thesis
Year: 2007
Downloads: 126
Quote: 0
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BACKGROUNDRecently, results from several population-based prospective studies validate theassumption that obesity is closely associated with the risk of atrial fibrillation (AF).Most of the studies, however, were conducted among white populations in westerncountries. Reports about Asian were limited. Furthermore, many developing countrieslike China have experienced rapid economic growth within recent decades. As anaftermath of changes in lifestyle and environment, the prevalence of obesity isincreasing at an unprecedented pace. Under such circumstances, this nationwidesurvey was conducted in fall 2004.OBJECTIVETo explore the relationship between obesity and AF, and to provide foundation foretiological studies and AF management.METHODSThe data from National 10th Five-year Plan Project(Non-valve atrail fibrillationpreventing thromboembolism, No.2001BA703B14) was used to analyze theassociation between obesity and atrial fibrillation(AF), which was directed to explorethe association between the AF and risk factors in fall 2004. The participants aged 35and above was recruited based on China Multicenter Collaborative Study ofCardiovascular Epidemiology (China MUCA Study) from 10 populations (Beijingrural, Beijing urban, Yuxian Shanxi Province, Jintan Jiangsu Province, Zhoushan,Zhejiang Province, Wuming Guangxi Province, Hanzhong Shaanxi Province, Deyang,Sichuan Province, Panyu Guangzhou Province and Mudanjiang HeilongjiangProvince) located in various parts of China. After excluding the people whose BMIwas less than 18.5 Kg/m2, a total of 18115 participants with complete informationwere valid to analyze, t test and chi square test were used to compare continuous variables and categorical variables.Multivariable Logistic regression was used toevaluate the relationship between obesity and AF.The AF was diagnosed by risk factor questionnaire or field ECG. It was defined as AFwhen either was positive. And then the AF patients performed the echocardiogram testand were ask to fill out a specific AF history questionnaire.Non-valve AF(NVAF) was defined as AF without valvular heart disease(VHD), and inthis study we further excluded 1 Af occurred within 30 days after surgeries and 4 AFsoccurred within 12 months after incidence of hyperthyroidism, when NVAF wasanalyzed.BMI was calculated by equation weight(Kg)/height(m)2. Underweight participants(BMI<18.5) were excluded to reduce the possibility of including individuals withcachexia. Normal-weight, overweight, and obesity were defined respectively asBMI<24, 24≤BMI<28, and BMI>28; the cut-off points of WC were 85/80 cm,95/90cm for men/women, based on the latest Chinese guideline for the obesityprevention and controll 11,12. WC<85/80cm(men/women) was defined as normal WC,85/80cm≤WC<95/90cm modestly increased WC, 95/90cm≤WC heavily increasedWC.RESULTSThere were 193 individuals with AF out of total 18115 participants, 89 men and 104women. The prevalence of AF was higher in men than in women and higher in theurban than the rural, the prevalence of AF significantly increased in participants agedover 60 years. The prevalence of overweight and obesity were 34.2% and 13.1%; theprevalence of modestly increased WC and heavily increased WC were 32.6% and16.0%. It was higher for AF patients in age, BMI, prevalence of myocardialinfarction(MI), the prevalence of left ventricular hypertrophy(LVH), the prevalence ofhypertension, the prevalence of diaetes mellitus and the prevalence of use alcohol etc..But the prevalence of hypercholesteremia was lower than non-AF patients.The prior studies had shown that the VHD, surgery and hyperthyroidism were the riskfactors of AF, but the project only had the AF patient to perform the echo test and to fill out the AF history questionnaire. Thus, these factors can not be controlled inLogistic regression model. We further analyzed the assiociation between AF andobesity after excluding these factors. The cause-specific ratio of AF was NVAF 71%,VAF?29%for men and NVAF 65%, VAF35%for women.1. The relationship between obesity and AF1) The relationship between BMI and AFThe prevalences of AF across three BMI groups were 0.9%, 1.1%and 1.7%.Age-adjusted prevalence was 1.02%in obese group. Prevalence of AF in normalweight group and overweight group were higher in men than in women. Theprevalence of AF were higher in the urban than in the rural. The prevalence of AF wasincreased sharply after 60 years. The presence rates of city, MI, hypercholesteremeia,hypertension, and diabetes increased across 3 BMI categories, while presence rate ofelectrocardiographic LVH decreased. When BMI was used as continuous variable inLogistic Regression model, it was significantly associated with risk of AF, OR was1.09(CI: 1.05-1.14). When BMI was used as categorical variable in LogisticRegression model, ORs in overweight and obese groups were 1.21(CI: 0.86-1.69) and1.88(CI: 1.26-2.81) compared to normal weight group, Ptrend<0.01. Association inmale, urban and elder was much closer.2) The relationship between WC and AF.The prevalence of AF across three WC groups were 0.8%, 1.1%and 1.9%. There wasno association between age and WC in men, while WC was increased with age inwomen. Prevalence of AF was increased with WC, and it higher in men than inwomen. When WC was used as continuous variable in Logistic Regression model,WC was significantly associated with risk of AF. ORs in men and women were1.03(CI: 1.01-1.06) and 1.03(CI: 1.01-1.05). When WC was used as categoricalvariable in Logistic Regression model, the ORs in male and female WC heavilyincreased groups were 2.53(CI: 1.41-4.56) and 1.57(CI: 0.95-2.59). 2. The relationship between obesity and NVAF§1) The relationship between BMI and NVAFAs we expected, BMI was associated with this kind of AF much more closely. Whenthis kind of AF was used as independent variable, the risk of AF was increased12%(CI: 6%-18%) with 1 unit increase of BMI after adjusted other factors. WhenBMI was used as categorical variable, the ORs in overweight and obese groups were1.53(CI: 0.99-2.35) and 2.39(CI: 1.44-3.98). Being different from total AF, therelationship between BMI and this kind of AF in women was more significant, whoseORs were 1.86(CI: 0.99-3.47) and 2.53(CI: 1.25-5.15) in overweight and obesegroups. It was probably because prevalence of valvar heart diseases was higher inwomen, the association between obesity and AF was enhanced after excluding effectof valvar heart diseases.2) The relationship between WC and NVAFThe association between WC and this kind of AF was closer too, especially in women.The risk of this kind of AF was increased 6%(CI: 3%-9%) with increase of 1cm WC.The ORs in WC modestly increased group and WC heavily increased group were2.35(CI: 1.16-4.76) and 3.37(1.61-7.08) compared with the normal WC in women. Itprobably resulted from WC was associated with cardiovascular diseases much closer,especially in these populations with low BMI, such as Chinese. BMI does not accountfor the wide variation in body fat distribution in this kind of populations. Meanwhile,BMI may be less useful indicator of adiposity among the elderly, who tend to have ashift of fat form peripheral to central sites but no increase in BMI. WC, however,compensates for this limitation of BMI, by bringing regional fat into consideration. Sowe further analyzed the combining effect of BMI and WC.3) Combining effect of BMI and WCThe combining effect of BMI and WC was further analyzed after excluding valvar AF,postoperative AF and hyperthyroidism AF. The entire population was subdivided in to18 groups, considering 2 sexes, 3 BMI groups and 3 WC groups. There was highestAF risk in WC heavily increased and obese group in men after adjusted for other risk factors, which was 3.28(CI: 1.45-7.43); there was highest risk of AF in WC modestlyincreased and obese group in women after adjusted for other risk factors, which was3.70(CI: 1.17-11.74); the AF risk of total population was generally increased withBMI and WC the OR of WC heavily increased and obese group was 2.85(CI:1.60-5.09) compared with the group with normal BMI and WC. It possibly suggestedthat bringing WC into consideration was more meaningful, when evaluating therelationship between BMI and AF.CONCLUSIONObesity is closely associated with risk of AF in Chinese middle aged and elderlypopulatins. The results indicated that BMI and WC are likely the independent riskfactors of AF; bringing WC into consideration may be more appropriate whenevaluating the relationship between BMI and AF. It is probably to prevent AF bycontrolling obesity.

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CLC: > Medicine, health > Internal Medicine > Heart, blood vessels ( circulatory ) disease > Heart disease > Arrhythmia
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