Matching for Body Mass Index in addition to Age and Gender May Make a Big Difference in Estimating Nutrient Intake in the Case-Control Studies

Reema F. Tayyem*
Department of Nutrition and Food Technology, Faculty of Agriculture, The University of Jordan, Amman, Jordan
*Corresponding Author Email Address: r.tayyem@ju.edu.jo

ABSTRACT
In almost all case-control studies, age and sex are the main confounders which we should match between cases and controls. The purpose of this matching is to attenuate the differences in outcomes results between cases and controls. By matching for age and sex only, the estimation of nutrients will be performed regardless of total energy intake, weight, body mass index (BMI) and physical activity level. The intake of macronutrients and some micronutrients estimated in most chronic diseases that are affected by diet, is usually higher in cases as compared to controls. This is attributed to the fact that controls should be apparently healthy which means that most of them should have normal or overweight. Accordingly, the nutrients intake was higher in cases than controls in most of the conducted studies. The effect of having higher intake of energy and consequently nutrients is usually controlled by adjusting for energy during the statistical analysis. Unfortunately, this adjustment does not make a remarkable difference between the crude and the adjusted data. However, matching for BMI could change the whole picture. Matching for age, sex and BMI between cases and controls will result in insignificant differences (in most situations) in energy intake between these two groups. In addition, matching in BMI will give a large similarity in the intake of macro- and micronutrients.
Nevertheless, few nutrients will show differences between cases and controls. On my opinion, the differences in these few nutrients could reflect the real association between the disease under investigation and nutrients intake. Although, matching for BMI may add burden on the researchers but this will seize the need to adjust for energy and more precise results may be obtained. More studies may be warranted to assure the favorable effect of matching for BMI in case-control studies that dealing with chronic diseases and diet history.

Keywords: Body Mass Index, Gender Difference, Nutrient Intake
Citation: Tayyem RF. Matching for Body Mass Index in addition to Age and Gender May Make a Big Difference in Estimating Nutrient Intake in the Case-Control Studies. Canad J Clin Nutr 2019; 7 (1): 113.
DOI: http://dx.doi.org/10.14206/canad.j.clin.nutr.2019.01.10

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