Body mass index growth in a sample of U.S. children: repeated measures data analysis of the Minneapolis Children's Blood Pressure Study.

Longitudinal assessments of the body mass index (BMI) in children and adolescents are limited. The purpose of the study was to describe the growth patterns of the BMI in children and young adults. Black and White children of Minneapolis Children's Blood Pressure Study (MCBPS) were 6 to 9 years old at entry and were followed for 12 years at 19 separate visits. Those with at least five visits (n = 1,302) were included for analysis, using non-linear mixed effects models in conjunction with the Gompertz curve. The growth patterns of four sex-ethnic groups were different at three levels: starting level (SL) (kg/m(2)), asymptote level (AL) (kg/m(2)), and peak growth age (PGA) (in years). In this context, SL is the average BMI level at age 6, AL is the average BMI level when growth diminishes, and PGA is the average age at which the rate of growth in the BMI peaks. The SL (16.3 +/- 0.1) for White males was significantly greater than SL in the other three sex-ethnic groups, among which there were no significant differences. There was a significant ethnic difference in AL between Black females (25.5 +/- 0.3) and White females (24.4 +/- 0.2) and a marginally significant difference in AL between Black females and Black males (24.4 +/- 0.3). For PGA, only sex differences were significant: Black females reached the peak at the earliest age at (11.5 +/- 0.1) years, followed by White females (11.7 +/- 0.1), Black males (12.6 +/- 0.1), and White males (12.8 +/- 0.1).

Response error in self-reported current smoking frequency by black and white established smokers.

As compared with white smokers, black smokers, although they report using fewer cigarettes per day, are at higher risk for most smoking-related diseases. Among black smokers serum cotinine levels are also higher in proportion to cigarettes per day; this observation has led to suggestions of bias in self-reporting. The purpose of this study was to evaluate and compare the extent of errors in self-reported smoking patterns among black and white established smokers. Ninety-seven white and 66 black smokers participated in structured telephone interviews, filled out two self-administered questionnaires one week apart, and collected all of their cigarette butts for a week. Group differences in the validity of self-reported smoking patterns were assessed by comparison with cigarette butt counts and the measured butt lengths. Both black and white smokers significantly overestimated smoking on our measure of smoking frequency (both P < 0.001); the group difference in bias was not significant (P = 0.13). There was no evidence that underreporting was more common among blacks than among whites (P = 0.67). Test-retest reliability was not significantly different in the two groups (P = 0.09). Both groups performed poorly when asked to categorize their smoking frequency according to the cutpoints of the Fagerström Test for Nicotine Dependence. Black smokers smoked more of each cigarette and smoked longer cigarettes, but they smoked fewer total millimeters of cigarettes per day (all P < 0.001). Contrary to an earlier report, the disproportionately high cotinine levels could not be attributed to reporting error.