Comparison between T1DM and the general population

Data from 186 T1DM patients were available for analyses. Of these 186 T1DM patients, 48.9% were female and 51.1% male with a mean age of 45 ± 15 years. The sample of the general Austrian population comprised 15,771 individuals, with the median age group between 45 and 49 years and an interquartile range of ±10 years. Baseline characteristics are shown in Table 1. Of the general population 4.7% reported having a diagnosis of diabetes, without further differentiation.

Table 1 Baseline characteristics T1DM and general population Full size table

The mean BMI of T1DM patients was 25.9 ± 4.2 kg/m2 and, controlling for age group, significantly higher than the mean BMI of the general population (25.3 ± 4.5 kg/m2, P = 0.027). Fig. 1 shows a scatterplot of BMI by age overlaid with age-specific median and 25th and 75th percentiles of BMI calculated in the general population. Of T1DM patients, 64 (34.4%) had a BMI higher than the age-specific 75th percentile, while only 46.5 (25%) would be expected (P = 0.010). Applying the commonly used categories, 39.8% of T1DM patients and 33.1% of the general population were overweight. The prevalence of obesity was 14% in T1DM and 13.8% in the general population; however, the differences in prevalence of overweight and obesity were not significant.

Fig. 1 Body mass index (BMI) of each T1DM in comparison with median, 25th and 75th percentile of general population in relation to age Full size image

Descriptive analyses of different age groups revealed that T1DM patients between 30 and 49 years had the highest BMI whereas in the general population BMI was highest in those aged 50–69 years (Table 1). In T1DM as well as in the general population the individuals younger than 30 years of age had the lowest mean BMI.

As ANOVA revealed evidence of heterogeneity in the differences in BMI between patients and the reference population across the age groups (interaction P = 0.017), those differences were tested separately for the four age groups. A significantly higher BMI in T1DM patients than in the reference population only in the age group between 30 and 49 years (26.7 ± 4.4 vs. 24.8 ± 4.3 kg/m2, corrected p < 0.001). This was further evidenced by the number of T1DM patients with BMI higher than the age-specific 75th percentile (observed: 35 out of 79, 44.3%; expected: 19.75, 25%; p < 0.001). The BMI values were not significantly different in the other age groups. Within the age group of 30–49 years it appears that female T1DM patients were responsible for the higher BMI as they had higher BMI values than their healthy counterparts (27.0 ± 5.1 vs. 23.9 ± 4.4 kg/m2, p < 0.001) in contrary to male patients where no significant difference could be found.

Metabolic parameters in T1DM

In T1DM patients the median duration of diabetes was 17 years (interquartile range, IQR: 10–27) and mean HbA1c level was 7.7 ± 1.3% (61 ± 14 mmol/mol) with 47.3% having good, 42.5% intermediate and 10.2% poor glycemic control. The average daily basal insulin dose was 23.4 ± 11.5 IU and 30 patients had additional antidiabetic medication, like metformin.

The T1DM patients had a mean systolic blood pressure of 136.4 ± 19.7 mm Hg and a mean diastolic pressure of 81.6 ± 10.6 mm Hg, while 44% (n = 78) had a diagnosis of arterial hypertension. Also, 14.6% (n = 19) had an albumin-creatinine-ratio above 30 mg/dl and were therefore diagnosed with albuminuria, with 11.5% (n = 15) in the category for microalbuminuria and 3.1% (n = 4) meeting the criteria for macroalbuminuria. Dyslipidemia was found in 23.3% of T1DM and in 27 prescriptions of statins was recorded. Further analysis showed that T1DM had cholesterol levels of 179.9 ± 37.1 mg/dl, LDL levels of 89 ± 30 mg/dl, HDL levels of 66 ± 20 mg/dl, and triglyceride levels of 100 ± 50 mg/dl.

There was no significant BMI difference between female and male T1DM (25.6 ± 4.4 vs. 26.2 ± 3.9; p = ns). As shown in Table 2, T1DM with a BMI ≥27.5 kg/m2 had significantly higher systolic and diastolic blood pressure, higher triglyceride levels and lower HDL-cholesterol levels than T1DM with a BMI <27.5 kg/m2. In addition, they more often had complications like albuminuria, especially microalbuminuria. Furthermore, as expected, the basal insulin dose was significantly higher compared to T1DM with a BMI <27.5 kg/m2. After adjusting each patients’ basal insulin dose by dividing it through their respective body weight the difference was still significant between the two groups. In contrast neither mean HbA1c nor prevalence of good or bad glycemic control was different between the BMI groups.