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Top of pageAbstractBackground: The majority of the studies have focused on the effect of general and central fat on coronary risk, neglecting the potential role of peripheral body fat.Objective: To assess the effect of surrogate measures for general, central and peripheral body fat on the occurrence of non fatal acute myocardial infarction (AMI).Methods: Population based case study; cases were patients aged 40 years consecutively hospitalized with an incident AMI (n and controls were community participants without previous AMI, selected randomly from the hospitals catchment area population (n Body mass index (BMI), waist circumference (WC),
hip circumference and a skinfolds composite index to estimate the proportion of peripheral subcutaneous fat in the arms were ascertained. Associations were summarized with odds ratios (OR) and 95 confidence intervals (95 CI), obtained from unconditional logistic regression with adjustment for the main confounders.Results: WC, and in particular waist to hip ratio (WHR), had strong direct associations with AMI risk replica van cleef and arpels flower earrings. Peripheral subcutaneous fat was inversely associated with AMI in women, but directly in men. Using principal component analysis, three uncorrelated factors were identified representing different patterns of fat distribution: (1) generalized fat, with high BMI and high WC; (2) central fat, with high WC and WHR; and (3) peripheral subcutaneous fat. The first factor showed no significant association with AMI, but the second factor increased AMI risk in each sex (upper vs lower fourth: OR 12.2, 95 CI 5.34 in women; OR 25.0, 95 CI 14.0 in men).Keywords: body fat distribution; peripheral fat; acute myocardial infarction; case study; principal component analysisTop of pageIntroductionObesity, often assessed by body mass index (BMI), has been related to several metabolic disorders,1 but its role on cardiovascular risk is still uncertain, because some studies have found a linear association with cardiovascular outcomes while others have reported J or U shaped associations or even no significant effects.2, 3, 4 Moreover, the amount and type of body fat distribution seem to be more important to cardiovascular risk than overall obesity per se replica van cleef and arpels butterfly earrings, because in several studies waist circumference (WC) and waist to hip ratio (WHR) were found to be better predictors of cardiovascular morbidity and mortality than total body weight and BMI.3, 5, 6, 7, 8, 9 WC has been more extensively used to identify individuals at high risk, due to its well documented positive association with cardiovascular disease,10, 11, 12, 13, 14 but WHR is attracting greater interest,5, 8 because of the role recently attributed to peripheral fat (fat located in upper and lower limbs) in the modulation of cardiovascular risk.Only a few studies have addressed the cardiovascular role of peripheral fat mass,15, 16, 17, 18, 19 which might be less atherogenic than abdominal fat, due to a low fatty acid turn over, and a differential hormone production.20, 21 Moreover, because women and men have different patterns of fat distribution,22 the association of peripheral fat with coronary outcomes might also vary with sex.Using data from a population based case study, we have examined the independent effect of surrogate measures for general, central and peripheral body fat on the occurrence of non fatal acute myocardial infarction (AMI) in each sex.Top of pageMaterials and methodsStudy design and participantsA population based case study was conducted among Portuguese Caucasian adults in Porto, a large urban center with almost 300 inhabitants in the northwest of Portugal.Cases were patients aged 40 years admitted consecutively, from 1999 through 2003, to the Cardiology Department of the four hospitals providing acute coronary care in Porto, who survived beyond the fourth day after a first AMI. Diagnosis of AMI was carried out with standard procedures.23Controls were selected from the non institutionalized adult population of the hospital's catchment area.
For each household identified by random digit dialing,24 permanent residents were characterized according to age and sex, and one participant was selected by simple random sampling.During the study period, 1106 patients aged 40 years with an incident AMI were identified. The following cases were excluded from the analyses: 60 who were unable to collaborate; 3 who refuse to participate; 34 who died before data collection; 82 who did not complete the interview; 133 with missing data on anthropometrics and 3 on selected confounders; and 138 with cognitive impairment. Out of 2000 community participants, the following were excluded: 103 (5.2 because of a previous AMI based on a self report or a 12 lead electrocardiogram; 121 for incomplete information on anthropometrics and 13 on selected confounders; and 50 with cognitive impairment. Therefore, analyses were conducted with 653 cases (163 women and 490 men) and 1713 controls (1065 women and 648 men).Data collectionData on cases and controls were collected by the same set of trained interviewers. Cases were interviewed during the hospital stay after clinical stabilization, and controls were invited to visit the Department of Hygiene and Epidemiology of the University of Porto Medical School to be evaluated.Anthropometrics Anthropometrics were performed with participants in light clothing and barefoot under standard procedures.26 Body weight was measured to the nearest 0.1 using a digital scale (SECA, Columbia, MO, USA) and height was measured to the nearest cm using a wall stadiometer (SECA, Hamburg, Germany). BMI was calculated dividing the weight in kg by the squared height in m replica van earrings.WC was measured midway between the lower limit of the rib cage and the iliac crest, and hip circumference on the maximum circumference over the femoral trochanters; both were measured to the nearest cm with a flexible and non distensible tape. SKF were grasped with the thumb and index finger approximately 1 proximal to the SKF site, which was measured to the nearest 0.5 Three measurements were taken for each SKF, obtaining the average value. A SKF composite index was calculated to estimate the proportion of subcutaneous fat of the arms ( triceps and biceps SKF triceps, biceps, subscapular and suprailiac SKF). Participants were classified into fourths of the distribution of the SKF composite index in controls.Confounders Data on potential confounders such as social, behavioral and clinical characteristics were collected with a standard structured questionnaire. Education was recorded as completed years of schooling. Participants were also classified as current smokers (daily and occasional smokers) and non smokers (never and former smokers quitting at least 6 months ago). Alcohol consumption was assessed with a validated semi quantitative food frequency questionnaire,28 concerning the previous 12 months. The intake of alcoholic beverages was converted into total alcohol intake using the software Food Processor Plus (ESHA Research, Salem, OR, USA, 1997). Physical activity corresponded to the regular practice (at least 30 per week) of any leisure time physical activity with energy expenditure higher than 2.5 metabolic equivalents per hour, including walking, running and the practice of any type of sport during the previous year.A family history of AMI was registered when one or more first degree relatives had suffered an AMI, regardless of the age at occurrence. Information on menopause and hormone replacement therapy was also recorded for all women. Individuals aged 65 or more years underwent a Mini Mental State Examination (MMSE)29 to assess cognitive function (those scoring in the Mini Mental State Examination were considered as cognitive impaired to provide reliable information).Statistical analysisCharacteristics of cases and controls were compared with the Mann test for continuous variables, and with the test or the Fisher's exact test, as appropriate, for categorical variables. Correlations between the anthropometric measures were evaluated by Spearman correlation coefficients.Principal component analysis30 with varimax rotation was used to identify factors representing uncorrelated components of body fat. The number of factors to identify must explain more than 90 of the total variance of anthropometry. Factor's interpretation was based on the correlations between the anthropometrics and the identified factors, obtained from the factor's loadings.The association between the anthropometric variables and the risk of AMI were summarized with odds ratios (OR) and their 95 confidence intervals (95 CI), obtained from unconditional logistic regression. ORs were adjusted for age, education and alcohol consumption, modelled as continuous variables, and for current smoking, regular physical activity, and menopause and hormone replacement therapy in women, modelled as categorical variables with dummy terms. The dose relationship between the anthropometric variables and AMI was assessed with tests for linear trend, by modelling the anthropometric measures as continuous variables.Analyses were conducted separately in each sex. We tested for sex interactions in analyses of the whole study sample using interaction terms, constructed as the product of sex by anthropometric variables. Statistical significance was set at P value Analyses were performed using Stata, version 9 (StataCorp. College Station, TX, USA).Top of pageResultsTable 1 shows the characteristics of AMI cases and controls, by sex. In women, cases were slightly older than controls, while the opposite was found in men. As compared with controls, cases had lower education, were less physically active, and reported more frequently a family history of AMI. Male cases had also a higher alcohol intake and reported a higher prevalence of smoking than controls.
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