recognized therapeutic range for a few days to a few weeks, the results suggest that rebound insomnia may present a clinical hazard. Two of the agents studied, flurazepam and diazepam, were not associated with rebound insomnia. Interestingly, the half-life of flurazepam and diazepam or of their active metabolites, or both, is longer than that of the other three agents. The report of Kales and colleagues, therefore, raises a question regarding a potential disadvantage of the use .of benzodiazepines with short half-lives in the treatment of insomnia. The laboratory sleep method is one of the most important tools available for studying the effects of drugs on sleep. Among other things, the subject's environment during sleep is carefully controlled and the continuous recording of the brain waves while the subject is asleep provides an objective measurement ROGER J. WOLSTENHOLME, B SC, M B,BS, of drug effects. Under these condiMRCP Cottage Hospital tions it is not surprising that difHarbour Breton, Nfld. ferences between various hypnotic agents can be demonstrated. These findings should further stimulate careful observation in clinical setClinical pharmacology and therapeutics of benzodiazepiues tings for similar but previously unrecognized differences between benTo the editor: As innovators in the zodiazepines with short and long development of benzodiazepines, half-lives. we at Hoffmann-La Roche Limited D.P. ZAROWNY, M Sc, MD wish to comment belatedly on Dr. Medical director Edward M. Sellers' concise review Hoffmann-La Roche Limited (Can Med Assoc J 118: 1533, Vaudreuil, PQ 1978). Dr. Sellers defined advantages and disadvantages associated with Reference the use of the various benzodiaze- 1. KALES A, SCHARF MB, KALES JD, pines available to Canadian physiet al: Rebound insomnia. JAMA 241: cians in 1978. More recent infor1692, 1979 mation suggests that there may be another clinically important difCanada Health Survey ference between various benzodia- The who will pay for it? zepines. In April 1979 Kales and col- To the editor: The question of payleagues1 reported the occurrence of ment for a controversial survey rebound insomnia, which they de- should be raised. There are a numfined as "an intense worsening of ber of segments of our society other sleep [that] consistently follows the than the government that have a abrupt withdrawal of certain ben- substantial interest in health. Prozodiazepine drugs". This observa- cessed food, tobacco and alcohol tion was based on the analysis of affect heath. The industries produc15 published laboratory sleep ing them have substantial advertising studies with five benzodiazepines budgets and should be asked to sup- triazolam, nitrazepam, flunitra- port an endeavour like the Canada zepam, flurazepam hydrochloride Health Survey, which Dr. P.P. and diazepam. Since the drugs were Morgan discussed recently in the administered at doses within the Journal (121: 148, 1979).

the 50 women 5 (aged 35 to 58 years) had had renal calculi and 8 had had bacteriologically proven urinary tract infections. Therefore, of the 100 adults 12 (7 men and 5 women) had had episodes of nephrolithiasis. Clearly, this may be a selected population but even so there does appear to be a high prevalence of nephrolithiasis in this group. Possible etiologic factors, such as hypercalciuria, hyperuricemia or other metabolic disturbances, have not been excluded. However, I believe it likely that both dietetic and, particularly, genetic factors may contribute significantly in this relatively isolated community. Because the population is stable, further epidemiologic studies with a larger group might confirm this high prevalence and elucidate the etiologic factors associated with nephrolithiasis in this area.

There is a precedent for such requests. I understand that the forestry industry will support a considerable portion of the forestry product research previously financed by the government. Many sceptics suspect that less reliance on government subsidy might also increase the relevance of health surveys. This greater reliance on private funding seems to me to be the "Spirit of Lalonde". To quote Marc Lalonde:1 Since direct health care is already consuming some 7% of the wealth that Canadians produce annually, it is evident that the rate at which the Government of Canada can expand its activities in the field of health is severely limited by financial considerations. WILLIAM A. McLEIsH, MD

Department of laboratory medicine

Ottawa General Hospital Ottawa, Ont. Reference 1. LALONDE M: A New Perspective on the Health of Canadians. A Working

Document, Govt of Canada, Ottawa, 1974

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