The effect of age on blink reflex excitability recovery

Background: The effect of age on blink reflex excitability recovery has not as yet been investigated.

Methods: We studied blink reflex excitability recovery bilaterally in 60 healthy volunteers (32 males, mean age=40.7, SD=13.2; 28 females, mean age=39.7, SD=12.1) following right supraorbital nerve stimulation with paired pulses (0.2ms constant current square pulses, 10 times sensory threshold intensity, 160, 300, and 500ms interstimulus intervals, ISI). Six responses were amplified, filtered (30–3000Hz), rectified, and on-line averaged. At least 15 seconds were interspersed between consecutive stimulus pairs.

Results: Multiple regression showed a significant influence of age, but not of gender, on blink reflex excitability recovery. Increasing age was inversely correlated with conditioned ipsi- and and contralateral R2 area with 300 and 500ms ISI (P<0.002 each), indicating less recovery. With 160ms ISI, there was no significant change with age.

Conclusion: These data indicate reduced excitability of brainstem interneuronal circuitry mediating the blink reflex with advancing age.