Scientific Concept of the National Cohort (status ... - Nationale Kohorte

A.3
A.3 Study design
genetics of BMI has recently been described 647 . Waist circumference is a common measure
of abdominal fat mass and can be obtained quickly. The ratio of waist circumference to hip
circumference has been used as an indicator for abdominal fat accumulation and fat distribution
among adults. The waist-to-hip ratio is a particularly informative predictor of vascular
risk, e.g., it is an additional predictor of incident MI 648 . The waist-to-height ratio is a further
simple index of body fat distribution that is only weakly associated with age but is highly
correlated with visceral fat mass among adults 649, 650 .
Procedure of measurement:
Measurements of waist and hip circumference will be taken with a flexible tape (e.g., Seca
201) according to a standardized protocol. Waist circumference will be measured at the
smallest position between the lower rib and the upper margin of the iliac crest. Hip circumference
will be measured at the widest part over the hips or buttocks region. The measurements
will take about 2 min. Measurements will not be taken in pregnant women (>12 th
week of pregnancy).
dual-energy X-ray absorptiometry
DXA is a noninvasive, easy to use, and relatively fast examination for assessing the three
body compartments bone mass, fat mass, and lean body mass. It is the gold standard procedure
to estimate bone mass and to predict bone fracture risk 651, 652 .
Comparing DXA to other techniques for assessing body composition (e.g., underwater
weighing) has shown that DXA correlates highly with other measures of body composition,
suggesting that DXA is an accurate method 653-655 . Historically, underwater weighing has
been considered the reference standard for the assessment of body composition. Due to its
ease of use and the fact that it provides a three-compartment model, DXA has the potential
of becoming a new reference standard 656 .
Procedure of measurement:
In a feasibility study it will be tested whether DXA measurement can also be applied in
observational studies with healthy subjects in Germany. Strict legal and administrative requirements
must be fulfilled. Furthermore, the specific device for DXA scans will be selected
within the feasibility study. The dose of radiation is very low (