The attack of Raynaud's phenomenon (RP) is characterized by finger blanching in response to cold or emotional stimuli.
To clarify the relationship between the attack of RP and air temperature, certain inhabitants of mountain village “T” (N₁=23) who had primary RP (PRP) were observed every day from August 20, 1990 to May 31, 1991 and those in town “K” (N₂=20) were observed from November 1, 1990 to May 31, 1991. One hundred and sixty-seven attacks of RP among 6 subjects in T Village and 89 attacks among 8 subjects in K Town were observed.
In T Village, the frequency of attacks was high in the morning, and the minimum and mean air temperatures in the days when some of the subjects had attacks (“attack days”) were significantly lower than those in the days when there was no attack on any subject (“non-attack days”). In K Town the frequency of attacks was high both in the morning and in the evening. In addition, the, mean and maximum air temperatures on the “attack days” were significantly lower than those on the “non-attack days.” The threshold temperature to cause RP attacks differed from one subject to another (5.2 to 17.6°C) in K Town during the period from November through February. The minimum air temperature which caused an attack of RP on any subject in T Village from August 20 to December 31 was 17.8°C.
These results suggest that cooling of the whole body in daily life promotes the onset of attacks of RP. When the minimum air temperature becomes lower than 18°C from autumn to winter, the whole body must be protected against cold to prevent the onset of RP.