The Relationship Between Waist Circumference and Biomarkers for Diabetes and CVD in Healthy Non-Obese Women. The Pensacola Study

Kristina Jackson Behan, PhD, MT(ASCP); Justice Mbizo, DrPH

Disclosures

Lab Med. 2007;38(7):422-427. 

In This Article

Discussion

Risk of Diabetes Mellitus

The risk of diabetes increases with age, BMI, hypertension, physical inactivity, dyslipidemia (low HDL or high triglycerides, or both), and inflammation, and is higher in non-Caucasians. In this study, women were similar in age and normal to overweight, and most of them were Caucasian. Women in the highest quartile of waist circumference had the highest BMI, the highest percent with hypertension, and the lowest percent that exercised. They also had the highest triglycerides, lowest HDL, and highest CRP of all of the groups. Five of the women had fasting glucose ≥ 100 mg/dL, the cutoff for prediabetes, and 13 had CRP > 3 mg/L. There were trends of increasing glucose and CRP across the WC quartiles. Other studies have found a correlation of increased WC with insulin resistance[7,18,19] and found that women with a WC between 32.3 and 35.6 inches (82 and 90.5 cm) had about 4 times the risk of becoming diabetic as women with a WC less than 29.5 inches (75 cm).[15] High CRP levels are associated with an increased risk for diabetes, independent of BMI, fasting insulin, and A1c.[5,6]

White blood cell count is another marker for inflammation, but it was not significantly different between the quartiles. Hemoglobin A1c is a marker of long term glycemic status, but it was not significantly different between the quartiles. It may be that the small difference in glucose levels in the study group was insufficient to affect a change in A1c. Furthermore, the accuracy of A1c values is influenced in opposite directions by iron deficiency and anemia of blood loss,[20,21,22,23] conditions found at a high prevalence in child-bearing and perimenopausal women.[24,25,26]

Risk of Cardiovascular Disease

The classic risk factors for CVD overlap those of diabetes, and include age, BMI, hypertension, physical inactivity, high cholesterol, diabetes, and inflammation. The prevalence of CVD is higher in non-Caucasians, smokers, and males. Waist circumference cutoffs of 32.7 and 36.6 inches, respectively (83 cm and 93 cm), were shown to be equivalent to a BMI of 25 and 30 with respect to the risk for CVD in white and black women.[16,17] The women in WC quartile 4 had waist measurements between 32.5 and 36.0 inches, putting most of them between the 2 cutoffs. Biomarkers of interest are the lipids and their ratios. Quartile 4 had the highest triglycerides, total cholesterol, and LDL, and the lowest HDL of all participants.

Ridker and associates followed a large cohort of healthy, middle-aged to elderly women over a 10-year period. They found that the 3 laboratory parameters with the highest predictive value for future cardiovascular events were non-HDL cholesterol, cholesterol/HDL, and CRP, with the hazard ratio for the women in the highest quintile of each parameter being 2.51 for non-HDL, 3.81 for cholesterol/HDL, and 2.98 for CRP.[27] Interestingly, the CRP was independent of the lipids, a finding consistent with other published works.[28] In the current study, women in Q4 had the highest median cholesterol/HDL ratio, the highest median non-HDL, and the highest median CRP. Women in Q3 had waist measurements between 28.5 and 32.0 inches (72.4 and 81.3 cm), and this quartile also showed significant differences in LDL, HDL, and cholesterol/HDL, though not to the extent of Q4.

The Value of WC Measurement

This study focused on healthy, non-obese, middle-aged women and found that those with the largest WC were significantly different than the other groups with respect to biomarkers that have customarily been used to predict future diabetes and cardiovascular events. Menopausal status did not alter these results.

Strengths of this study are that it was specific for females and middle age, and that the lipid and glucose results are true and not influenced by lipid- or glucose-lowering medication. A limitation is that the percentage of non-Caucasians was low. Race is a risk for both diabetes and CVD, and these results may be different in a more diverse study group. Data on exercise and health status are self reported. Three women were not aware of their menopausal status due to hysterectomy. They were classified as postmenopausal to account for the effect of menstrual bleeding on A1c. It is unlikely that this small number of participants would affect the results if they were misclassified, since none of the correlation coefficients between WC and the laboratory biomarkers changed significantly after adjustment for menopause. Women in this study volunteered to participate in response to advertising, which presumes that they are actively involved in their health. The study group, therefore, is biased toward educated health-care consumers, which may have some effect on the lipid and glucose values found. As a cross-sectional study, their actual progression to diabetes or CVD cannot be ascertained.

The goal in preventive health care is to identify subjects with increased risk and do something about it. Several studies have shown the success of intervention strategies, including weight loss, increased physical activity, and modifications in fat consumption[7,29,30] as well as drug therapy[3,30] in preventing or delaying T2DM and heart disease. A WC measurement done in a clinical setting along with BMI provides information about abdominal fat and is a measurement the general public is familiar with. It is a measurement that can be done easily at home. Furthermore, women are cognizant of weight gain around the middle, even without actually measuring it. In other studies, a WC greater than 83 cm showed a 1.56 odds ratio for incident CVD independent of BMI in white and black women[16,17,31] and 4 times the risk for incident T2DM.[15] In the present study, subjects with a WC greater than 32.5 inches (82.6 cm) showed significant changes in the conventional biomarkers for diabetes and cardiovascular disease, reaffirming WC as an appropriate clinical action threshold.

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