IJCS | Volume 33, Nº4, July and August 2020

363 (DBP), waist circumference (WC), body fat percentage, body mass index, glycemia, sexual maturation index or sleep quality. Nonetheless, although WC was not statistically different between the groups, the size of the effect showed high clinical relevance when comparing the groups. The HRV of the Control and the FHD groups are shown in Figure 1 and Table 2. No statistically significant differences were observed between the groups in the time domain variables RR average, pNN50 (%) and total variance (ms²), but differences were observed in SDNN, RMSSD, SD1, and SD2. The variables LF (ms²) and HF (ms²), in the frequency domain, also showed statistical differences. The other frequency domain variables in normalized units – LF (nu) and HF (nu) – and the LF/HF balance did not show significant differences. However, it is important to highlight that both LF/HF and the total variance (ms²) showed to have a significant clinical impact when the effect size was evaluated. Discussion The main finding of this study was a decrease in vagal activity in children of diabetic parents before the manifestation of any change in glycemia, suggesting an impairment in cardiac autonomic modulation. These results can be observed in the HRV of the participants, which does not corroborate the study by Rocha et al., 8 which compared the autonomic function of individuals aged 18 to 49 years, with and without a family history of type 2 DM (DM2) in the absence of glucose intolerance. In this study, the authors observed differences in BMI, serum lipids, leptin, and C-reactive protein, in addition to similar autonomic parameters between the groups. In contrast, our results indicated earlier changes in HRV, which, in turn, corroborate the study by Iellamo et al., 19 which showed that these changes occur primarily in individuals with diabetic parents. Anthropometric indices, sexualmaturation, Pittsburgh’s sleep quality, SBP, DBP, blood glucose and physical activity level were not significantly different between the groups, showing that theywere not determining factors to changes in the HRV. However, WC showed a high effect, a result that corroborates studies that relate abdominal fat accumulationwith the increase ofWC as an important risk factor for the development of DM2. 20, 21 In addition, it was possible to notice a reduction in HRV in individuals with a family history of diabetes, with worse cardiac autonomic modulation, resulting in greater sympathetic activity. 22-24 This suggests that altered autonomic function would precede the onset of glycemic dysfunction, which corroborates the study by Table 1 - Body composition of adolescents without a family history of diabetes (controls) and adolescents with a family history of diabetes (FHD) Controls (n = 46) FHD (n = 23) p Effect size Age (years) 16.41 ± 1.33 16.16 ± 1.8 0.52 0.16 Height (cm) 163.3 ± 1.173 159.9 ± 1.717 0.10 2.47 Weight (kg) 57.00 ± 1.617 53.97 ± 2.085 0.26 1.69 Waist circumference (cm) 72.4 ± 1.160 70.29 ± 1.462 0.27 1.66 Body fat (%) 26.79 ± 1.374 26.07 ± 1.465 0.74 0.51 Body mass index (kg/m²) 21.33 ± 0.518 21.02 ± 0.612 0.71 0.56 Systolic blood pressure (mmHg) 112.45 ± 2.332 113.54 ± 1.542 0.75 0.51 Diastolic blood pressure (mmHg) 65.16 ± 1.102 67.24 ± 1.595 0.28 1.61 Glycemia 87.15 ± 11.216 83.31 ± 10.725 0.35 0.34 Sexual maturation index 2.92 ± 0.611 2.89 ± 0.311 0.63 0.05 Pittsburgh 1.54 ± 0.658 1.47 ± 0.611 0.65 0.10 IPAQ 1.34 ± 0.487 1.62 ± 0.517 0.21 0.56 IPAQ: International Physical Activity Questionnaire; data presented as mean ± standard error; Student’s t-test. Controls vs FHD (p < 0.05). The size effect was calculated according to the Hedges’g method. Dias-Filho et al. Family history of diabetes and autonomic nervous system Int J Cardiovasc Sci. 2020; 33(4):360-367 Original Article