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Predictors of Weight Outcomes, Dietary Behaviors, and Physical Activity in
Coronary Artery Risk Development in Young Adults Study (CARDIA)
Cora E. Lewis, MD, MSPH for the CARDIA Investigators
University of Alabama at Birmingham
Agenda and Abstracts
CARDIA study is a prospective, epidemiologic investigation of the determinants and evolution of cardiovascular risk factors among 5,115 African American and white young adults 18-30 years of age at baseline in 1985-86. Participants were recruited from the populations of four geographic locations (Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA). The study population was approximately balanced according to sex (54% women), ethnicity (52% African American), and education (40 % with less than equal to 12 years of education) at each center. Additional examinations were undertaken at years 2 (1987-88), 5 (1990-91), 7 (1992-93), 10 (1995-96), and 15 (2000-01). Overall retention rates for follow-up examinations were: 90 percent, 86 percent, 81, 79 percent, and 74 percent of surviving participants, respectively (approximately 2.5 percent were deceased as of the year 15 examination) over the 15 year follow-up.
Weight and height were measured at each exam using the same equipment and protocols; baseline height was used to determine BMI. A quantitative food frequency questionnaire was interviewer-administered at baseline and year 7, as was a symptom-limited maximum treadmill exercise test. Physical activity, and a variety of behavioral, psychosocial, attitudinal, and socioeconomic factors were assessed by self-report.
As of the 15 year examination, the average participant had gained: 16 kg for BW, 10.1 kg for WW, 14.1 kg for BM and 11.1 kg for WM, and of these groups 48%, 26%, 41%, 29%, respectively, gained greater than equal to 15 kg. Large increases in obesity prevalence had occurred in all groups.
In general, lifestyle variables potentially related to overweight were associated with each other. Frequent fast food intake was related to a higher intake of refined grains and soft drinks and lower intake of fruits and vegetables at baseline. At year 5, hours per day of TV viewing was inversely associated with physical activity, education, income, and with hostility and depression (in whites) scores.
Over the first 7 years of follow-up, overall treadmill duration decreased 10 percent, ranging from a 15 percent decrease in African-American men to a 7 percent decrease in white women. Dietary intake improved in terms of cholesterol and saturated fat intake and Keys score. There was some evidence for tracking for both physical activity and diet with many participants maintaining their relative ranking on these two variables.
Findings of relationships of lifestyle and other factors with weight change vary depending on the time period evaluated and/or the specific dependent variable examined. Between baseline and year 2, weight gain of at least 5% was associated with greater baseline BMI, previous dieting, considering oneself too fat, and the report of previous loss of 10 lb or more, compared to those whose weight remained stable. Over the first 7 years, change in physical fitness explained the greatest amount of the variance in weight change; each 60 second decline in exercise duration was associated with an average weight gain of 2.1 kg in women and 1.5 kg in men. Other factors significantly associated with greater 7-year weight gain in both sexes were ex-smoker status, younger baseline age, greater baseline percent energy from fat, lower baseline fitness, and ethnicity (men).
Over the first 10 years, dietary fiber was inversely related to weight gain in both African Americans and whites. The 10-year incidence of obesity was inversely related to dairy intake in those overweight at baseline but not in those initially normal weight.
Over 15 years, baseline fast food consumption (frequency per week) was independently related to weight increase in both African Americans and whites, and increased fast food consumption from baseline to year 15 was related to weight increase in whites. There was a particularly strong relationship among those least physically active at baseline. When 18 baseline behavioral, psychosocial, attitudinal, and socioeconomic factors were examined for associations with 15-year weight gain of greater than equal to 15 kg, comparing to those participants who maintained a stable weight (within 5 kg of baseline), only 8 variables (age, overweight at baseline, alcohol intake, considering oneself too fat, job demands, report of previous dieting, physical activity and physical fitness) were significant predictors of large weight gain, and none was significant in more than 2 of the 4 race-sex groups. There were no associations for fast food, fat, or carbohydrate intake, or TV watching.
Large increases in weight and obesity have occurred during follow-up in CARDIA. These increases have affected all four major demographic groups. Associations with potential predictors have been inconsistent across analyses.
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