Research article

A case-control study of sporadic Creutzfeldt-Jakob disease in Switzerland: analysis of potential risk factors with regard to an increased CJD incidence in the years 2001–2004

Jessica Ruegger^{* 1} , Katharina Stoeck^{* 2,3} , Lorenz Amsler^4,5 , Thomas Blaettler^2,6 , Marcel Zwahlen⁷ , Adriano Aguzzi² , Markus Glatzel^2,8 , Klaus Hess¹ and Tobias Eckert^4,9

¹Department of Neurology, University Hospital Zurich, Zurich, Switzerland

²Institute of Neuropathology, University Hospital Zurich, Zurich, Switzerland

³Department of Neurology, University Hospital Hamburg-Eppendorf, Hamburg-Eppendorf, Hamburg, Germany

⁴Federal Office of Public Health, Bern, Switzerland

⁵CSL Behring, Bern, Switzerland

⁶Bristol-Myers Squibb, Wallingford, CT, USA

⁷Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland

⁸Institute of Neuropathology, University Hospital Hamburg-Eppendorf, Hamburg-Eppendorf, Hamburg, Germany

⁹Swiss Tropical Institute, Basel, Switzerland

author email corresponding author email* Contributed equally

BMC Public Health 2009, 9:18doi:10.1186/1471-2458-9-18

Published:	14 January 2009

Abstract

Background

In 2001, the observed annual mortality from Creutzfeldt-Jakob disease (CJD) in Switzerland increased from less than 1.5 to 2.6 per million inhabitants. An underlying cause could not be identified.

Methods

To analyse potential risk factors for sCJD in Switzerland, close relatives of 69 sCJD-patients and 224 frequency age-matched controls were interviewed in a case-control study using a standardised questionnaire. 135 potential risk factors including socio-demographics, medical history, occupation and diet were analysed by logistic regression adjusting for age, sex and education.

Results

sCJD patients were more likely to have travelled abroad, worked at an animal laboratory, undergone invasive dental treatment, orthopaedic surgery, ophthalmologic surgery after 1980, regular GP visits, taken medication regularly, and consumed kidney. No differences between patients and controls were found for residency, family history, and exposure to environmental and other dietary factors.

Conclusion

Although some factors were significantly more frequent among sCJD-cases, this study did not reveal specific explanations for the increased incidence of deaths due to sporadic CJD observed in Switzerland since 2001. Results have to be interpreted with caution due to multiple testing and possible recall bias in association with a long incubation period. The most plausible reason for the increase in Swiss sCJD cases after 2000 is an improved case ascertainment. Therefore, underreporting of cases might well have occurred before the year 2001, and the "real" yearly incidence of sCJD might not be lower than, but rather above 2 per million inhabitants.