IJCS | Volume 33, Nº4, July and August 2020

365 Fiorentini et al., 25 with 75 individuals with a mean age of 47.71 years, divided into a group with a family history of DM2 and insulin resistance, a group of descendants with a family history without insulin resistance and a control group. The authors identified that changes related to the reduction in autonomic system function were associated with a family history of diabetes. 25 The results in this study showed changes in cardiac autonomic modulation suggestive of lower vagal activity, which was also noted in the study by Kardelen et al. 26 in children with an average age of 12 years and insulin dependence. The time-domain RMSSD (ms 2 ) and SDNN variables confirmed a lower cardiac autonomic modulation in children of diabetic parents found in the analysis of adjacent RR intervals, 27 reflecting a decrease in vagal activity. 28 Therefore, a significant decrease in RMSSD and SDNN is indicative of a reduction in vagal tone and greater modulation of the cardiac sympathetic autonomic nervous system as shown in adolescents in the family history of diabetes group, corroborating previous studies. 26,29,30 Analysis of the frequency domain revealed that HF (ms²) and LF (ms 2 ) indices are lower in children of diabetics, corroborating the studies by Chen et al. 31 and Malik et al., 32 including DM2 children aged from eight to 12 years, showing a decrease in the LF (ms 2 ), HF (ms 2 ) components, as well as in total variance. Although our study did not show significant differences in total variance, this parameter showed a high effect size, indicating important clinical representativeness. The LF/HF ratio, a marker of autonomic imbalance, was lower in children with parents with DM2. This is different from the study by Fiorentini et al., 25 which identified changes in LF/HF ratio indicating lower vagal activity in 70 Caucasian individuals, mean age of 47 years, descended from parents with DM2. The failure to identify autonomic imbalance in the present study may be related to the age range of the groups in our study, since autonomic nervous system disorders in insulin- resistant patients are closely related to longer exposure to the disorder. 33,34 However, it is important to emphasize that the LF/HF balance showed a strong effect, supporting it as an important marker of clinical changes in cardiac autonomic modulation in adolescents with a family history of diabetes. The SD1 andSD2 values indicateda lower vagal activity in the FHD group, which corroborates the findings of Kaminski et al. 35 who evaluated the sympathovagal activity in adult individuals. However, their sample comprised individuals aged 11 to 18 years incomplete, whichmakes the findings important evidence for a better understanding and early identification of an association of cardiac autonomic dysfunction with a genetic factor in the etiology of this condition. First-degree relatives of individuals with DM2 are known to have two to six times greater risk of developing the disease compared with individuals with no family history of diabetes. 36 In this case, the genetic component is a determining factor, where the possibility of individuals with a family history of diabetes is five to ten times higher for the development of the disease than the general population. 37 In terms of clinical and scientific relevance of the findings, some points need to be highlighted. First, in the studies reviewed, there was little scientific evidence, since HRV in adolescents with a family history of diabetes has been poorly studied and deserves further investigation. Our findings may be used in subclinical detection of autonomic dysfunctions, definition of the risk level, and in early diagnosis of hemodynamic and autonomic changes in offspring of individuals with DM. This would reduce overall mortality and the risk of the development of DM2, metabolic complications and other noncommunicable chronic diseases. In interpreting these results, some limitations need to be considered. The study allowed verifying the existence of a family history of diabetes among participants, however, it was not possible to determine the type of DM in the parents; also, insulin and lipid levels of these individuals were not assessed, which could have provided relevant clinical information and should be explored in future studies. Conclusion Global autonomic modulation is decreased in adolescents with a family history of diabetes. It was also observed a vagal activity decrease (RMSSD and SD1 indices), indicating that a sympathetic modulation is predominant in this population. Acknowledgements Credit to FAPEMA and the CINTRA School Teaching Group for their support to the development of this research. Dias-Filho et al. Family history of diabetes and autonomic nervous system Int J Cardiovasc Sci. 2020; 33(4):360-367 Original Article