Epidemiological study in Switzerland.

Attention was first drawn to the association between analgesic abuse and chronic renal damage by Spuhler and Zollinger in 1950 [1]. Between that time and 1967, many studies attempted to investigate the nature of this association, yet none of these were able to assess quantitatively the extent of the relationship between excessive use of analgesics and subsequent development of urorenal disorders. What seemed to be needed was a longitudinal study in a healthy population which would incorporate reliable and valid measurements of analgesic use as well as urorenal disorders. With this in mind, an epidemiologic study was designed in Switzerland using a study population of apparently healthy women who were 30 to 49 years of age. A previous investigation had indicated that heavy intake of analgesics is more prevalent in women than in men and most prevalent in women of this age group [2]. This study was designed to be conducted in four phases as outlined: Phase 1 (completed 1968) was a two-stage screening procedure to establish a study group of women, aged 30 to 49 yr, who show evidence of high intake of phenacetin-containing analgesics and a matched control group of women who show no such evidence of high intake. Phase 2 (also completed 1968) was an interview and examination of both study and control groups, and phase 3 (completed 1972) was a follow-up of these women, including yearly examinations from 1969-72. Phases 1, 2, and 3 have been reported elsewhere [3, 4]. Phase 4 was started in 1975: it consists of further follow-ups at three-year intervals. The present report concerns the incidence of urorenal disorders in the study and control groups during the last follow-up in 1975.