Association of Novel Oral Appliance Use With Heart Rate Variability in Adolescent Athletes

BACKGROUND The Lin Oral Appliance (LOA) is a novel oral device intended to reduce snoring. Heart rate variability (HRV) can noninvasively represent autonomic function. We investigated whether LOA use influences autonomic modulation in adolescent athletes using HRV indices. MATERIAL AND METHODS This prospective study analyzed HRV in time and frequency domains. RMSSD, SDSD, and p.NN50 represented parasympathetic activity; low-frequency (LF)/high-frequency (HF) ratio represented sympathetic balance. Two-way repeated-measures analysis of variance evaluated associations of sex and test sequence. Associations between test sequence and RMSSD or LF/HF were examined via repeated-measures multiple linear regression with generalized estimating equations. RESULTS Forty-three adolescent athletes (23 boys, 20 girls) were enrolled (age, 14.8±1.6 years; body mass index, 21.8±2.5 kg/m²; training duration, 2.7±1.6 years). RMSSD and SDSD were strongly correlated (r>0.832, P<0.001). LF/HF was positively correlated with LF (r=0.339, P<0.001) and negatively correlated with HF (r=-0.234, P=0.002). After LOA use, RMSSD significantly increased (mean difference, 12.2; P=0.007); p.NN50 also increased. In generalized estimating equation models adjusted for autocorrelation, test round (10 minutes per round) was a significant positive predictor of RMSSD (P<0.001); RMSSD and LF/HF did not differ by sex. CONCLUSIONS Adolescent athletes exhibited a significant increase in parasympathetic activity across tests. This increase may be associated with LOA use during test 2. Future studies should incorporate sham controls, randomized and counterbalanced designs, and concurrent respiratory monitoring to explore causality and elucidate underlying mechanisms.