[Algesimetric experiment on pain sensitivity in the pericranial musculature. Circadian rhythms and corresponding psychic variables.].

Many types of headache that occur in the form of attacks show a notably high incidence at certain times of the day. Attacks are often accompanied by emotional instability, irritability, exhaustion and other impairments of well-being. The cause for the frequent daytime occurrence of attacks is not clear. One possible explanation could be the variability in a person's sensitivity to headache over the course of the day. For this reason we set out to investigate whether pain sensitivity to experimentally-induced headache varies in a circadian manner and whether this variation correlates to changes in the current state of well-being over the course of the day. In 24 healthy, voluntary subjects, headache was induced experimentally at 0200, 0600, 1000, 1400, 1800, and 2200 hours. Blood criculation in both superficial temporal and occipital arteries was reduced by applying a cuff to the head and inflating it to 200 mmHg, thereby producing a continuously increasing, bilateral, dull, frontal headache. The subjects scaled the intensity continually, using the category subdividing procedure ranging from pain threshold to pain tolerance level. In addition, 17 dimensions of the current state of well-being and 12 personality traits were recorded at the above-mentioned times in a standardized quantitative manner. At low levels of headache intensity there were no significant differences in pain sensitivity. Sensitivity to very intense headache, however, varied significantly over the course of the day: sensitivity was greatest at 0200 hours; it decreased at a constant rate until 1400 hours, and increased again continuously until 2200 hours (P</=0.05). Sensitivity to low levels of headache intensity did not prove to be significantly correlated to dimensions of current well-being. By comparison, however, the findings showed significant correlations between sensitivity to very high headache intensities and multiple dimensions of the current state of well-being. These findings show that headache sensitivity follows circadian patterns. Daytime variations, however, are only significant for sensitivity to high intensities. Thus these results may explain, in part, why violent attacks of pain occur predominantly at night and in the early morning.