NR AAWB
AU Aylin,P.; Bunting,J.; de Stavola,B.; Coleman,M.P.
TI Mortality from dementia in occupations at risk of exposure to bovine spongiform encephalopathy: analysis of death registrations.
QU British Medical Journal 1999 Apr 17; 318(7190): 1044-5
IA http://bmj.bmjjournals.com/cgi/content/full/318/7190/1044
KI BMJ. 1999 Apr 17;318(7190):1045. PMID: 10336285
PT journal article
VT
Since the early 1980s close contact with animals or animal products infected with bovine spongiform encephalopathy has posed a putative risk of infection with Creutzfeldt-Jakob disease. Several groups with potentially high exposure have already been identified [1].
To study whether transmissible spongiform encephalopathy has had any effect on people working in animal husbandry and slaughter, we used national mortality records to examine patterns of mortality from Creutzfeldt-Jakob disease and other dementias during 1979-80 and 1982-96.
Subjects, methods, and results
We studied people who died aged 20-74 years during 1979-1996 in England and Wales and for whom the occupational information recorded at death included butcher and abattoir worker, farmer and farm worker, or veterinarian. Women were selected on the basis of their own occupation, if recorded, or on the occupation of their spouse.
The causes of death selected for study were Creutzfeldt-Jakob disease (ICD-9 046.1) and a wide range of dementias, including those most likely to be misdiagnosed as Creutzfeldt-Jakob disease [2]. It was not possible to separate deaths from new variant disease. There were in any case too few deaths from new variant Creutzfeldt-Jakob disease within the study period (13 deaths during 1994-6 [3]) to include them as a separate category.
We calculated the age standardised proportional mortality ratio for each occupational group and each disease category. The 95% confidence intervals were calculated by assuming that the observed number of events followed a Poisson distribution. The data were grouped into four periods (1979-80 and 1982-3, 1984-7, 1988-91, and 1992-6). Sex specific linear trends in the proportional mortality ratio over time were examined by fitting a Poisson regression model [4] to the observed numbers of deaths in each year, with the year and the expected number of deaths as the explanatory variables. The estimated risk ratios for successive calendar years represent the average linear change over time in the proportional mortality ratios.
During the study period, 4,145,898 deaths were registered in people aged 20-74. Of these, 92,365 occurred in farmers, 22,596 in butchers, and 970 in veterinarians. In farmers and farm workers only 12 deaths were attributed to Creutzfeldt-Jakob disease (table). Deaths from dementia (including Creutzfeldt-Jakob disease seemed to fall in men but there were no significant trends. In women the proportional mortality ratios remained relatively constant. No deaths were recorded from Creutzfeldt-Jakob disease in butchers or abattoir workers. In men, the proportional mortality ratio for dementias increased from 62 (95% confidence interval 23 to 134) in 1979-83 to 119 (70 to 188) in 1992-6, but the change was not significant. In women, there was no evidence of a linear trend. No veterinarians died from Creutzfeldt-Jakob disease during the entire period and only six died from dementia.
-----------------------------------------------------------------------------------
Numbers of deaths, proportional mortality ratios (PMR), and 95% confidence intervals for Creutzfeldt-Jakob disease (CJD) and dementia among men and women aged 20-74 in selected occupational groups, England and Wales, 1979-96
Occupation and Total 1979-83* 1984-7 1988-91 1992-6 Annual linear
cause of death No of No PMR(95%CI) No PMR(95%CI) No PMR(95%CI) No PMR(95%CI) trend in PMR
deaths Risk P
Farmers and farm workers ratio value
CJD:
Men 7 2 239(29-862) 1 91( 2-506) 0 - 4 254(69-652) 1.05 0.65
Women 5 2 195(24-704) 2 131(16-474) 0 - 1 65( 2-364) 0.73 0.32
Dementia including CJD:
Men 247 41 106(76-143) 88 98(78-119) 63 82(62-103) 55 82(61-104) 1.03 0.77
Women 258 41 98(70-133) 76 87(67-106) 75 89(69-109) 66 105(80-130) 0.82 0.35
Butchers and abattoir workers
CJD:
Men 0 0 - 0 - 0 - 0 - - -
Women 0 0 - 0 - 0 - 0 - - -
Dementia including CJD:
Men 66 6 62(23-134) 23 98(62-147) 19 101(61-158) 18 119(70-188) 1.03 0.30
Women 67 11 113(56-202) 26 123(81-181) 17 80(47-129) 13 91(49-156) 0.97 0.25
Veterinarians
CJD:
Men 0 0 - 0 - 0 - 0 - - -
Women 0 0 - 0 - 0 - 0 - - -
Dementia including CJD:
Men 4 0 - 0 - 3 359(74-1049) 1 132( 3-735) 1.21 0.23
Women 2 0 - 1 127( 3-708) 0 - 1 109( 3-608) 1.20 0.33
*Occupational data were not available for 1981 owing to industrial action by registrars of births and deaths in that year.
-----------------------------------------------------------------------------------
Comment We found no increase in deaths from Creutzfeldt-Jakob disease or other dementias during 1979-96 among these occupational groups. Among farmers and farm workers there were four deaths certified as due to Creutzfeldt-Jakob disease in men and one in a woman during 1992-6, but the proportional mortality ratios are not higher than might be expected by chance. The study, assuming 80% power, would be able to detect at least 1.5 additional deaths in male farmers each year with 95% confidence.
It is difficult to monitor trends in rare diseases such as Creutzfeldt-Jakob disease because of small numbers of deaths and doubts about the precision of diagnosis and certification of death. However, surveillance of deaths in these occupational groups will remain necessary to identify promptly any trends in mortality from Creutzfeldt-Jakob disease or its new variant.
We thank Dr R Will at the National CJD Surveillance Unit in Edinburgh for advice in the planning phase of this study, and the constructive criticism of earlier drafts by Gillian Dollamore at the Office for National Statistics.
Contributors: JB was responsible for the extraction and interpretation of the data. BDeS conducted the statistical analysis and contributed to interpretation and reporting. MPC contributed to the study design, interpretation, and drafting the report. PA took the initiative in this study and contributed to the study design, analysis, interpretation of the results, and drafting the paper. PA is the guarantor.
Funding: Department of Health and Medical Research Council.
Competing interests: None declared.
1 Roberts GW. Furrowed brow over mad cow. BMJ 1995;311:1419-20.
2 Will RG, Mathews WB. A retrospective study of CJD in England and Wales 1970-79. I. Clinical features. J Neurol Neurosurg Psychiatry 1984;47:134-40.
3 National CJD Surveillance Unit. Creutzfeldt-Jakob disease surveillance in the UK. Sixth annual report. Edinburgh: NCJDSU, 1997.
4 Breslow NE, Day NE. Statistical methods in cancer research. Vol II. The design and analysis of cohort studies. Lyons: IARC, 1987:168-71. (IARC scientific publications No 82.)
-----------------------------------------------------------------------------------
ZR 4 Zitate
MH Adult; Aged; Animal Husbandry; Animals; Cattle; Creutzfeldt-Jakob Syndrome/*mortality; Death Certificates; Dementia/*mortality; Encephalopathy, Bovine Spongiform/*transmission; England/epidemiology; Female; Food-Processing Industry; Humans; Male; Meat Products; Middle Aged; Occupational Diseases/*mortality; Occupational Exposure/statistics & numerical data; Wales/epidemiology
AD
Paul Aylin (senior clinical lecturer), Department of Epidemiology and Public Health, Imperial College of Medicine at St Mary's, London W2 1PG
Julia Bunting (researcher) und Michel Coleman (deputy chief medical statistician), Health and Demography, Office for National Statistics, London SW1V 2QQ
Department of Epidemiology and Population Health, London School of Hygiene and Tropical Bianca De Stavola (senior lecturer), Medicine, London WC1E 7HT
Correspondence to: Dr Aylin p.aylin@ic.ac.uk
SP englisch
PO England
OR Prion-Krankheiten 1