| Is the ratio of flow-mediated dilation and shear rate a statistically sound approach to normalization in cross-sectional studies on endothelial function? | |
| | |
MedLine Citation:
|
PMID: 19833808 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
It has been deemed important to normalize flow-mediated dilation (FMD), a marker of endothelial function, for between-subject differences in the eliciting shear rate (SR) stimulus. Conventionally, FMD is divided by the area under the curve of the SR stimulus. In the context of a cross-sectional comparison across different age cohorts, we examined whether this ratio approach adhered to established statistical assumptions necessary for reliable normalization. To quantify brachial artery FMD and area under the curve of SR, forearm cuff inflation to suprasystolic pressure was administered for 5 min to 16 boys aged 10.9 yr (SD 0.3), 48 young men aged 25.3 yr (SD 4.2), and 15 older men aged 57.5 yr (SD 4.3). Mean differences between age groups were statistically significant (P < 0.001) for nonnormalized FMD [children: 10.4% (SD 5.4), young adults: 7.5% (SD 2.9), older adults: 5.6% (SD 2.0)] but not for ratio-normalized FMD (P = 0.10). Moreover, all assumptions necessary for reliable use of ratio-normalization were violated, including regression slopes between SR and FMD that had y-intercepts greater than zero (P < 0.05), nonlinear and unstable relations between the normalized ratios and SR, skewed data distributions, and heteroscedastic variance. Logarithmic transformation of SR and FMD before ratio calculation improved adherence to these assumptions and resulted in age differences similar to the nonnormalized data (P = 0.03). In conclusion, although ratio normalization of FMD altered findings about age differences in endothelial function, this could be explained by violation of statistical assumptions. We recommend that exploration of these assumptions should be routine in future research. If the relationship between SR and FMD is generally found to be weak or nonlinear or variable between samples, then ratio normalization should not be applied. |
| | |
Authors:
|
Greg Atkinson; Alan M Batterham; Mark A Black; Nigel T Cable; Nicola D Hopkins; Ellen A Dawson; Dick H J Thijssen; Helen Jones; Toni M Tinken; Daniel J Green |
Related Documents
:
|
16313458 - Female common lizards (lacerta vivipara) do not adjust their sex-biased investment in r... 11085698 - The male/female ratio of fetal deaths and births in japan. 16461288 - Sex allocation conflict in ants: when the queen rules. 3905518 - Erythrocyte flow velocity changes with age and sex in augmented supraorbital, superfici... 17598138 - Ptsd symptoms in children and adolescents 28 months after a flood: age and gender diffe... 532538 - Prediction of postoperative hypoxemia in smokers and non-smokers. |
Publication Detail:
|
Type: Journal Article Date: 2009-10-15 |
Journal Detail:
|
Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 107 ISSN: 1522-1601 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2009 Dec |
Date Detail:
|
Created Date: 2009-12-02 Completed Date: 2010-02-02 Revised Date: - |
Medline Journal Info:
|
Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
|
Languages: eng Pagination: 1893-9 Citation Subset: IM |
Affiliation:
|
1Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom. g.atkinson@ljmu.ac.uk |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Adult Age Factors Aging / physiology* Area Under Curve Blood Flow Velocity Brachial Artery / physiology* Child Cross-Sectional Studies Endothelium, Vascular / physiology* Forearm / blood supply, physiology Humans Male Middle Aged Models, Statistical* Regression Analysis Vasodilation / physiology* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: When energy balance is maintained, exercise does not induce negative fat balance in lean sedentary, ...
Next Document: Permanent alveolar remodeling in canine lung induced by high-altitude residence during maturation.