Pseudogout: timing of attacks and the cosmogeophysical environment.

OBJECTIVE To search for a time parallelism between lunar and solar rotation cycles and calendar dates of attacks of pseudogout--chondrocalcinosis articularis (pyrophosphate arthropathy). METHODS Seventy-four documented attacks with known calendar dates of onset recorded in 16 patients of one family cluster between 1955 and 1995 were examined in this study. Their daily frequencies during the given time span (chronogram) were transformed into frequencies pertaining to separate days of the corresponding cycle (plexogram). The latter data were processed by the cosinor analysis to test the presence of a priori supposed periodicities. RESULTS The most pronounced time parallelism was found with the Bartels solar rotation cycle, covering a period of 27 days. The cosinor regression explained 95% of the total variance in the data. The plexogram of the attacks displayed 4 clear peaks and 4 troughs. Besides the 27-day cycling, its 2nd, 3rd, 4th and 5th harmonics, i.e. approximately 14-, 9-, 7- and 5 day rhythms were also statistically significant. Some periodic changes were also found during lunar cycles. The maximum frequency was encountered shortly after the full moon and after the moon perigee. CONCLUSION A causal connection between fluctuations of the geomagnetic field, such as that during solar rotation and perhaps also lunar cycles, and the occurrence of pseudogout attacks could exist and should be studied more extensively.