Waist-to-Height Ratio and Coronary Artery Disease in Type 1 Diabetes
Central obesity may be more than a cosmetic concern in people with type 1 diabetes. A long-term Finnish cohort study found that a higher waist-to-height ratio (WHtR), a simple measure of abdominal fat, was linked to a greater risk of coronary artery disease (CAD). The association was especially clear among participants who did not yet have albuminuria, an early sign of kidney damage.
Why abdominal fat matters
Body fat distribution can influence cardiovascular risk even when body mass index is not markedly elevated. Fat stored around the abdomen is metabolically active and is associated with insulin resistance, inflammation, abnormal lipid levels, and higher blood pressure. In type 1 diabetes, these factors can add to the already elevated risk of blood vessel damage.
The waist-to-height ratio is calculated by dividing waist circumference by height. A ratio of 0.5 or higher is commonly used to define central obesity. Compared with body mass index, WHtR may better reflect cardiometabolic risk because it captures abdominal fat rather than overall body size alone.
What the study examined
This analysis used data from the Finnish Diabetic Nephropathy Study, a large cohort of 4,349 people with type 1 diabetes and no prior CAD at baseline. Researchers followed participants for a median of 19 years to see whether central obesity was associated with future coronary events.
The main outcomes included acute myocardial infarction, coronary revascularization procedures such as angioplasty or bypass surgery, and death related to coronary artery disease. The investigators also examined whether the relationship differed across albuminuria categories: normoalbuminuria, microalbuminuria, and macroalbuminuria. Albuminuria refers to the presence of albumin in the urine and is a marker of kidney injury and vascular risk.
Key findings
During follow-up, 664 CAD events occurred, representing 15.3% of the cohort. People with central obesity had noticeably higher cumulative CAD incidence over time. At 10 years, the cumulative incidence was 11.6% in those with central obesity compared with 4.4% in those without it. At 20 years, the difference widened to 25.3% versus 9.9%.
In multivariable Cox regression models adjusted for baseline clinical factors, each 0.1-unit increase in WHtR was associated with a 21% higher risk of CAD overall. The hazard ratio was 1.21, with a 95% confidence interval of 1.06 to 1.38 and a statistically significant P value of 0.006.
Among participants without albuminuria, the association was even stronger. In this subgroup, each 0.1-unit WHtR increase corresponded to a 26% higher CAD risk, with a hazard ratio of 1.26 (95% CI, 1.02 to 1.56; P = 0.03).
What the results mean
These findings suggest that WHtR may be a useful and practical tool for identifying type 1 diabetes patients at higher cardiovascular risk. Because it is easy to measure in routine care, it could help clinicians spot individuals who may benefit from more intensive risk-factor management.
The stronger association in those without albuminuria is particularly important. Kidney disease is already a well-known marker of cardiovascular risk in diabetes, but this study indicates that central obesity may signal elevated CAD risk even before kidney damage becomes apparent. In other words, a normal urine albumin result does not rule out meaningful cardiovascular risk if abdominal obesity is present.
Possible biological explanations
Several mechanisms may explain why central obesity increases CAD risk. Excess abdominal fat can promote chronic low-grade inflammation, worsen blood sugar variability, increase triglycerides, lower protective HDL cholesterol, and raise blood pressure. It may also contribute to endothelial dysfunction, meaning the inner lining of blood vessels does not work properly. Over time, these changes favor atherosclerosis, the buildup of plaque in the coronary arteries.
In type 1 diabetes, long-term exposure to hyperglycemia already accelerates vascular injury. Adding central obesity may amplify this process and make coronary events more likely.
Clinical implications
This study supports a more active focus on waist-related measurements in people with type 1 diabetes, not just weight or BMI. In practice, clinicians may consider the following:
Regular measurement of waist circumference and height to calculate WHtR
Assessment of blood pressure, lipids, kidney function, and albuminuria
Lifestyle counseling aimed at reducing abdominal fat through diet quality, physical activity, and smoking cessation
Optimization of glycemic control while avoiding frequent hypoglycemia
Appropriate use of statins, antihypertensive therapy, and other cardiovascular preventive measures when indicated
For patients, the message is straightforward: maintaining a healthy waist size relative to height may be an important part of protecting the heart, even in type 1 diabetes.
Strengths and limitations
The study has several strengths, including a large sample size, long follow-up, and detailed assessment of cardiovascular outcomes. It also evaluated risk across albuminuria categories, which adds clinical relevance.
However, as an observational cohort study, it cannot prove that central obesity directly causes CAD. Some residual confounding is possible, meaning other unmeasured factors may have influenced the results. In addition, WHtR was measured at baseline, so changes in body shape over time were not fully captured.
Bottom line
In this 19-year cohort study of people with type 1 diabetes, a higher waist-to-height ratio was associated with a greater risk of coronary artery disease. The relationship was especially strong in those without albuminuria. WHtR is a simple, low-cost measure that may help identify patients who need closer cardiovascular prevention and follow-up.
