How do statistical properties influence findings of tracking (maintenance) in epidemiologic studies? An example of research in tracking of obesity.

Published

Journal Article

There is great interest in studying the tracking (maintenance) of health conditions and risk factors over the life span. Tracking is often defined as the maintenance of a distribution position (e.g., quintile or percentile) in a study population over time. This study investigated how statistical properties might influence research findings of tracking with a special attention on the tracking of extreme ranking. Our results show that when repeated measures over time were positively correlated, the probability of tracking in extreme rankings was greater than other rankings and this was closely influenced by the overall correlation (r) and by the categorization. For example, when r = 0.4, 38% remained in the bottom and upper quintile (Q1, Q5) respectively, while only 22% remained in the middle quintile (Q3); when r = 0.8, the figure became 65% vs. 32%. When r = 0.4 and 0.8, 19 and 50% remained in the upper 95th percentile (or under the 5th percentile), respectively. Our real data show that children in the upper body mass index (= weight(kg)/height(m)(2)) quintile were more likely to maintain their ranking (54%) than others (about 30%), but not significantly higher than the expected (47%, p > 0.05). In conclusion, the overall correlation should be considered when studying tracking. Our proposed methods and predicted probabilities of tracking can help test whether one's observed tracking patterns are different from the statistically predicted ones.

Full Text

Duke Authors

Cited Authors

  • Wang, Y; Wang, X

Published Date

  • January 2003

Published In

Volume / Issue

  • 18 / 11

Start / End Page

  • 1037 - 1045

PubMed ID

  • 14620937

Pubmed Central ID

  • 14620937

Electronic International Standard Serial Number (EISSN)

  • 1573-7284

International Standard Serial Number (ISSN)

  • 0393-2990

Digital Object Identifier (DOI)

  • 10.1023/a:1026196310041

Language

  • eng