Waist-height ratio predicts severe diabetic eye disease risk in T1D

Waist-height ratio (WHtR), a hallmark of central obesity, appears to be a good indicator for the risk of developing severe diabetic eye disease (SDED) in adults with type 1 diabetes (T1D), results of a 15-year cohort study suggest.

“This study supports the inclusion of WHtR beyond body mass index (BMI) in the routine consultation of individuals with T1D,” the researchers said.

Of the 5,401 adults with T1D in the Finnish Diabetic Nephropathy Study, 3,468 were assessed and 437 underwent dual-energy X-ray absorptiometry for body composition analysis. SDED, the composite outcome, was defined as proliferative retinopathy, laser treatment, antivascular endothelial growth factor treatment, diabetic maculopathy, vitreous haemorrhage, and vitrectomy.

The researchers performed logistic regression analysis to examine the associations between body compositions and SDED and multivariable Cox regression analysis to assess the links between anthropometric measures and SDED. They also conducted a subgroup analysis by stages of albuminuria. The relevance ranking of each variable was based on the z statistic.

A total of 886 SDED events occurred during a median follow-up of 14.5 years. Visceral/android fat ratio correlated with SDED (odds ratio [OR], 1.40; z, 3.13), as did percentages of visceral (OR, 1.80; z, 2.45) and android fat (OR, 1.28; z, 2.08) but not the total body fat percentage. [J Clin Endocrinol Metab 2022;107:e653-e662]

WHtR had the most robust correlation with the SDED risk (hazard ratio [HR], 1.28; z, 3.73), followed by waist (HR, 1.01; z, 3.03), BMI (HR, 1.03; z, 2.33), and waist-hip ratio (WHR; HR, 1.15; z, 2.22). Results were similar in normo- and microalbuminuria but not significant in macroalbuminuria. Specifically, a WHtR ≥0.5 raised the risk of SDED by 28 percent at the normo- and microalbuminuria stages.

“The weaker association … between BMI and SDED compared to the association between WHtR and SDED may be due to the lower power of BMI [relative] to WHtR to estimate the visceral fat in individuals with T1D, according to previous research of our group,” the researchers said. [Sci Rep 2020;10:18575]

“The observed differences between BMI and WHtR are even more relevant in clinical practice since, given that in the present data set, 10.7 percent of the individuals with normal BMI and 69.1 percent of those with higher-than-normal BMI presented a WHtR ≥0.5, which means that several individuals at high risk of SDED would not be recognized if only a BMI ≥30kg/m² is considered as a risk factor,” they added.

Central fat, estimated by WHR, has been shown to correlate with diabetic retinopathy in studies of individuals with type 2 diabetes. [Acta Diabetol 2010;47:209-215; JAMA Ophthalmol 2016;134:251-225]

However, the present study found WHR to be the last of four anthropometric measures in the ranking of relevance. Beyond that, WHR did not correlate with SDED in subgroup analysis according to diabetic nephropathy stages.

“To understand the disagreement with the literature, it is important to recognize that the present study included individuals with T1D, which differs from those with type 2 diabetes in many aspects,” the researchers said, adding that WHR is inferior to WHtR as an estimator of visceral fat. [Sci Rep 2020;10:18575]

“In other words, it seems that visceral fat is the main factor for SDED; therefore, the stronger the association between the anthropometric measure and visceral fat is, the better predictor it is,” they added.