QT Interval Duration is Related to Obesity and Physical Activity Level for African American Women and Children

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Medicine & Science in Sports & Exercise


The Q-T interval indicates the time required for the ventricles to undergo a single cycle of depolarization and repolarization. Long QT interval is predictive of sudden cardiac death and has been observed in obese patients. Although it is well known that physical activity reduces incidence of obesity, little is known about the QT interval duration in African American Women and their daughters or the effects of obesity and physical activity level (PA)on QT duration.

PURPOSE:This descriptive study was conducted to determine if degree of obesity or PA is significantly correlated with QTc (QT interval duration corrected for heart rate), in a group of African American mothers (ages 21–53 yr) and their daughters (5-17 yr) (n = 44 and 66, respectively).

METHODS: Apparently healthy, inner-city African American women with daughters volunteered and gave informed consent to participate. Subjects were 12-14 hours fasted when blood was drawn, PA were estimated, and electrocardiograph (ECG) and blood pressure measurements were made. Data were blocked by the body mass index (BMI) for normal weight (BMI < 25), overweight (BMI 25-29.99), and obesity (BMI > 30) and ANOVA tests run to determine differences in QTc between the groups. Correlations were run between all variables.

RESULTS: Percentages of normal weight, overweight and obesity for mothers and daughters were 18, 23, 59 and 59, 29, 12, respectively. Results indicate a significantly longer QTc(p = 0.003), and significantly higher systolic and diastolic blood pressure values (SBP and DBP), (p = 0.003) and fasting glucose levels (p = 0.039) for obese compared to normal-weight mothers and daughters. QTc was positively associated with waist circumference (r = 0.85), and SBP(r = 0.65) and DBP (r = 0.62) for mothers, but not daughters. Average PA for 63% of combined mothers and daughters was 4.58 MET-hr/wk, compared to the Surgeon General's recommendation of 7.5-15 MET-hr/wk. There was an inverse association between self-reported PA and QTc for mothers and daughters, which reached significance (p < 0.001) for the obese daughters.

CONCLUSION: These results indicate a positive association between obesity and long QTc and an inverse association between exercise and long QTc. Additional research is needed to determine potential independant and interactive effects of exercise and obesity on QTc for African American women and their daughters. Supported by the Graduate School and Department of Health and Sport Science, University of Dayton.

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Medicine & Science in Sports & Exercise is the official journal of the American College of Sports Medicine.


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