ABSTRACT
Prevalence There have been three simple descriptive surveys but as yet no sound cross-sectional population survey. A prevalence of 10% was recorded from entrants to a Boston medical library while a higher figure of 21% was obtained amongst employees of a Swedish pharmaceutical company. A study conducted in England and Australia produced figures of 14.8% and about 5% which confirmed the observation of PLE being commoner away from the equator.1
