Abstract 18524: Heart Rate Variability and Cardiovascular Fitness are Lower in Non-hispanic Black versus Non-hispanic White Adolescents With Type 1 Diabetes

Abstract

Type 1 diabetes mellitus (T1D) is growing worldwide with the incidence peaking at puberty. Current population projections indicate that the numbers will nearly triple by 2050 with the prevalence primarily among minority racial/ethnic groups. Future diabetes-related morbidity, mortality and health care expenditures associated with poor cardiovascular (CV) outcomes are of paramount concern. In adolescents with T1D, heart rate variability (HRV) is noted to be lower when compared with healthy control subjects. Current research also supports a level of physical activity for adolescents with T1D that does not meet American Heart Association guidelines of 60 minutes of moderate-to-vigorous intensity per day, leading to decreased levels of physical fitness and elevated HbA1c. T1D Exchange (a large national epidemiological study) found that only 14% of Non-Hispanic Black (NHB) versus 34% Non-Hispanic White (NHW) youth met the American Diabetes Association HbA1c targets of < 7.5%, potentially increasing the odds of poorer outcomes in NHB youth.The hypotheses were that HRV and CV fitness would be lower in NHB versus NHW adolescents with T1D and that those with poorer glycemic control would have lower HRV and CV fitness. Methods: A sample of 96 adolescents with T1D (n = 67 NHW; n = 29 NHB) participated. Using 24-hour holter recordings, both spectral and time domain measures of HRV were obtained. Cardiovascular fitness (V02peak) using a graded exercise test was completed. HbA1c was obtained using the Siemens/Bayer DCA 2000. Findings: There were no significant differences in age (15.4 ± 1.9 vs. 15.0 ± 1.9 years) or duration of diabetes (6.6 ± 3.8 vs. 5.3 ± 3.4 years). Resting diastolic BP, recent and average HbA1c (values averaged over 1 year) were significantly higher (p < 0.05) and measures of HRV and fitness were significantly lower in NHB versus NHW adolescents (p < 0.001). While average HbA1c was associated with lower CV fitness in both NHB and NHW groups (r = -.44 vs. -.25, p < 0.05, respectively), lower measures of HRV were associated with poor glycemic control (HbA1c) only in NHBs (r = -.37 to -.43, p < 0.05). Conclusions: Findings support the importance of early identification of CV health disparities in adolescents with T1D, particularly variation experienced in NHB youth.