Figure 1

Change in LH in relation to time of light exposure. Change in urinary LH excretion (mIU/ml) is expressed as the LH stimulation index. This is a change index calculated by computing the ratio of the post-treatment LH excretion rate divided by the baseline (pre stimulus) rate, and then taking the log (base 10) of this fraction. In this way, a decrease producing a ratio of < 1.0 gives a negative log value. Each point is plotted relative to the internal circadian time of the midpoint of the 3 h light stimulus. Zero h represents circadian midnight, defined as 3.52 h prior to the time of the aMT6s acrophase in the pre-stimulus phase assessment. The key to symbols identifies the points by age and gender of the participants, N = 98. The black line presents a 3-hour moving average of the points, with dotted lines showing 95% confidence intervals of the mean.