BACKGROUND: The Amsterdam Growth and Health Longitudinal Study (AGAHLS) is a 20 y observational study concerning biological, psychological and lifestyle risk factors for cardiovascular disease and osteoporosis. In the AGAHLS two cohorts can be distinguished: the so-called Multi-Measurement Group (MMG), which received eight repeated measurements, and a Bi-Measurement Group (BMG), which received two measurements, one at the beginning and one at the end of the 20 y period.
OBJECTIVE: In health-related longitudinal research, the outcomes of the study may be influenced by the measurements themselves and the health information provided. It was hypothesized that the repeated measurements and the health information given to the MMG would result in a more healthy dietary intake in comparison to the BMG.
DESIGN: The MMG consisted of 164 subjects and the BMG consisted of 90 subjects. At the start of the study, subjects were teenagers of 13-y-old. The hypothesis was tested with use of regression analysis, analysing group differences in mean individual change scores.
RESULTS: Only the MMG showed a significantly larger decrease in the intake of mono- and disaccharides compared to the BMG.
CONCLUSIONS: The effect of the repeated measurements and the health information provided on dietary intake was relatively small, since it was only one out of the 14 nutrients that differed between the MMG and the BMG.