Objective: The aim of the present cross-sectional study was to evaluate the autonomic nervous system by dynamic pupillometry (DP) in normotensive and hypertensive individuals with either a non-dipper-type or a dipper-type circadian rhythm of blood pressure (BP).
Patients and methods: A total of 80 patients were allocated into four groups: normotensive/dipper (n=23), normotensive/nondipper (n=19), hypertensive/dipper (n=18), and hypertensive/nondipper (n=20). Pupil diameters (R0, R1, R2, and R%): latency (Lc), amplitude (Ac), velocity (Vc), and duration (Tc) of pupil contraction: latency (Ld), velocity (Vd), and duration (Td) of pupil dilatation were measured by DP. Among the DP parameters, Vc and Ac were known parasympathetic indices and R% was the major sympathetic index.
Results: Vc and Ac were higher in the dipper normotensives with respect to nondipper normotensives (Vc=5.19±0.85 vs. 4.58±0.71, P=0.017; Ac=1.66±0.27 vs. 1.49±0.28, P=0.048). Vc and Ac were higher in dipper hypertensives with respect to the nondipper subgroup of hypertensive cases (Vc=4.44±0.81 vs. 3.94±0.45, P=0.024; Ac=1.47±0.26 vs. 1.27±0.11, P=0.004). R% was higher in the nondipper subgroup of hypertensives than the dipper subgroup of hypertensive cases (36.7±4.8 vs. 33.5±3.8, P=0.033). Correlation analyses showed moderate positive correlations of night-time decline in BP with Vc (r=0.460, P=0.001) and Ac (r=0.420, P=0.001). There was also a negative correlation between night-time decline in BP and R% (r=-0.259, P=0.001).
Conclusion: Nondipping in BP is associated with lower parasympathetic activity both in normotensive and in hypertensives cases. Furthermore, in the nondipper subgroup of hypertensive cases, there is higher sympathetic activity than the dipper subgroup.