NR AQBW
AU Hofman,A.; Wientjens,D.P.W.M.
TI Epidemiological evidence concerning a possible causal link
QU British Medical Journal 1995 Nov 25; 311(7017): 1418-9
IA http://bmj.bmjjournals.com/cgi/content/full/311/7017/1418
PT Article
VT
The occurrence of Creutzfeldt-Jakob disease in British dairy farmers possibly exposed to cattle with bovine spongiform encephalopathy has focused attention on the possibility of a causal link between the two diseases. We briefly review the currently available epidemiological evidence.
The table shows the incidence of Creutzfeldt-Jakob disease in France, Germany, Italy, the Netherlands, and Britain. The data are based on registries in the countries, which have used similar methods of surveillance and criteria for diagnosis since the start of a European collaborative study in 1992. The incidence in Britain, with a much higher risk of exposure to bovine spongiform encephalopathy, was similar to that in the other European countries.
The epidemiological evidence concerning occupational exposure derives from two sources- a meta analysis of three case-control studies, conducted in Japan, Britain, and the United States[iv]; and an ongoing European case-control study based on the registries of Creutzfeldt-Jakob disease that were started in 1992.[v] The meta-analysis included data on 178 cases of Creutzfeldt-Jakob disease and 333 controls. In 95 cases information on occupational exposure to cattle was available, and 26 subjects had been exposed. The corresponding figures for the controls were 26 out of 145. The resulting relative risk for exposure (adjusted for age and sex) was 1-7 (95% confidence interval 0 9 to 31).
lncidence of Creutzfeldt-Jakob disease per million person years in European countries in 1993 and 1994[i,ii]
France Germany Italy Netherlands Britain
1993:
No of cases* 28 19 31 10 32
Incidence 0.50 0.47** 0.54 0.68 0.56
1994:
No of cases* 47 58 30 16 54
Incidence 0.81 0.73 0.53 1.04 0.93
*Includes probable and definite cases according to criteria adapted from Masters et al
**Extrapolated from figures for June to December 1993.
A preliminary analysis from the ongoing European case-control study included 234 cases of people with the disease, of whom 24 had ever been occupationally exposed to cows, and 237 controls, of whom 19 had ever been exposed. The relative risk amounted to 13 (95% confidence interval 0 7 to 2 5) (personal communications from A Alperovitch and N Delasnerie-Laupretre, France; S Poser and T Weber, Germany; C Masullo and M Pocchiari, Italy; A Hofman and D P W M Wientjens, Netherlands; and R G Will, Britain).
Although the occurrence of Creutzfeldt-Jakob disease in four dairy farmers in Britain is clearly a matter of concern, the current evidence from the European surveillance study suggests that there is no higher risk of the disease in British dairy farmers than in farmers in other European countries. Furthermore, the overall incidence of Creutzfeldt-Jakob disease is similar in the five European countries, while there is a substantial difference in the incidence of bovine spongiform encephalopathy. Taken together, the epidemiological evidence to date does not point to a causal link between bovine spongiform encephalopathy and Creutzfeldt-Jakob disease but, unfortunately, does not strongly reject that possibility either.
i. Alperovitch A, Brown P, Weber T, Pocchiari M, Hofman A, Will R. Incidence of Creutzfeldt-Jakob disease in Europe in 1993. Lancet 1994,343:918.
ii. Delasnerie-Laupretre N, Poser S, Pocchiari M, Wientjens DPWM, Will R. Creutzfeldt-Jakob disease in Europe. Lancet 1995;346:898.
iii. Masters CL, Harris JO, Gajdusek DC, Gibbs CJ Jr, Bernoulli C, Asher DM. Creutzfeldt-Jakob disease: patterns of worldwide occurrence and the significance of familial and sporadic clustering. Ann Neurol 1979;5:177-88.
iv. Wientjens DPWM, Davanipour Z, Hofman A, Kondo K, Matthews WB, Will RG, et al Risk factors for Creutzfeldt-Jakob disease: a reanalysis of case control studies. Neurology (in press)
v. Hofman A. Risk of Creutzfeldt-Jakob disease in relation to animal spongiform encephalopathies: a collaborative study in Europe. Eur J Epidemiol 1991;7:466-8.
ZR 5
AD Albert Hofman professor of epidemiology Dorothee P W M Wientjens research physician, MRC Comparative Cognition Team Department of Experimental Psychology School of Clinical Veterinary Medicine Cambridge CB3
SP englisch
OR Prion-Krankheiten H