Influences of long- and short-distance driving on alpha waves and natural killer cell activity

We examined the effective amplitudes of alpha waves (using a mean frequency with a range of +/- 0.5 Hz), and activity of natural killer cells in six subjects, before and after a short-distance (43 km, 1 hr.) drive, and after a midnight (am 0:00-am 7:00 to 8:00) long-distance (550 km on average, for 7 to 8 hr.) drive. Following a long-distance drive, the activity of natural killer cells tended to decrease, and the effective amplitudes of alpha waves in the photic feedback period were greater than those observed during the rest period, showing that photic driving had occurred even under physically and mentally stressful conditions. However, after short-distance driving, no photic driving response occurred and activity of natural killer cells tended to increase, possibly related to mental concentration. Avoiding midnight long-distance driving may help prevent excessive stress and preserve high activity in natural killer cells.