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Dementia in twins
remained culture positive for at least a year, during which time the rat population doubled in size. In the UK in the 1930s and 1940s several outbreaks of salmonellosis in people were linked to Salmonella-based rodent bait.2 This type of rodenticide could easily cause foodborne disease in people. Salmonella Enteritidis of a variety of phage types, including 6a, is recognised globally as a human foodborne pathogen and is particularly likely to be transmitted through eggs from chickens with ovarian infections.3 Infected rodents may play an important role in sustaining the infection on egg-producing farms.4 Salmonella-based rodenticides were banned in the USA, Germany, and the UK in the 1920s, 1930s, and 1960s, respectively. In 1967, the World Health Organization recommended that salmonella-based rodenticides not be used because they imposed a public health hazard.5 The use of Salmonella-based rodenticides in the developing world in the 1990s once again poses a public health risk. The effectiveness of these products is, to our knowledge, undocumented by field studies on wild rodent populations. All strains of Salmonella serotype Enteritidis are presumed to be pathogenic for humans. The risk of using these bacterial pathogens to control rodents outweighs any potential benefit they may have. Public health officials world wide should be aware of this so they may take steps to prevent illness that Salmonella-based rodenticides are likely to cause.
rats
showed that
some rats
R Friedman, Georgia Malcolm, José G Rigau-Pérez, Primo Arámbulo III, Robert V Tauxe *Foodborne and Diarrheal Diseases Branch, DBMD, Dengue Branch, DVBID, NCID, Centers for Disease Control and Prevention, Atlanta GA 30333, USA; and Veterinary Public Health Program, Pan American Health Organization/World Health Organization, Washington DC
*Cindy
1 2 3
Rosenau MJ. The inefficiency of bacterial viruses in the extermination of rats. Public Health Bull 1910; 40: 179-204. Taylor J. Bacterial rodenticides and infection with Salmonella enteritidis. Lancet 1956; i: 630-34. Mishu B, Griffin PM, Tauxe RV, et al. Salmonella enteritidis gastroenteritis transmitted by intact chicken eggs. Ann Intern Med
1991; 115: 190-94. 4
5
Henzler DJ, Opitz HM. The role of mice in the epizootiology of Salmonella enteritidis infection on chicken layer farms. Avian Dis 1992; 36: 625-31. Anonymous Joint FAO/WHO expert committee on zoonoses. World Health Organ Tech Rep Ser 1967; 378: 1-127
various types of dementia is evaluated retrospectively. In our study, the linkage of the registers according to the first diagnosis yielded the monozygotic/dizygotic ratio 1.2. When the linkage was done with four diagnoses, the ratio was 1.5. After review and adjustment for age, the ratio climbed to 1.8. Another point is that the linkage of registers yielded only a few twin pairs concordant for ICD code 290 (senile dementia) and the most concordant co-twins were not found until the validation of diagnosis. Dementia in a co-twin had been recorded in hospital notes but a diagnosis of dementia was not concluded at the discharge. In the analysis of Danish twins, the frequency of concordant pairs was not stated. This would have been of interest in comparing the two data sets. *I
Räihä, J Kaprio, M Koskenvuo, T Rajala, L Sourander
Departments of *Geriatrics and Public Health, University of Turku, 20700 Turku, Finland; and Department of Public Health, University of Helsinki Christensen K, Holm NV, Vaupel JW. Lancet 1996; 347: 976. Räihä I, Kaprio J, Koskenvuo M, Rajala T, Sourander L. Alzheimer’s disease in Finnish twins. Lancet 1996; 347: 573-77.
1 2
Will
today
be the
day YOU hear from "J"?
SiR-Drowning in medical reading? Can’t even keep up with all the junk mail? Maybe you, too, have lately received an advertisement ripped out of an un-named medical journal, with a "post-it" attached from "J" saying: "Try this. It’s really good!". The advertisement extols the benefits of American Medical Digest, a journal summarising reports in 150 other medical journals, which can be subscribed to for a year at the introductory rate of$195. The impression is created that a benevolent friend in the USA has thoughtfully torn out the article, attached the "post-it", and written to you, a busy academic, with some good advice on how to "stay completely informed-despite your tight schedule". The ruse is uncovered (or is it?) upon the realisation that one does not know a "J" in the USA; "J" has not put his/her address on the envelope-and further inquiries quickly locate other colleagues who have received the same apparently personal letter from "J" (who must subscribe to a ton of journals in order to rip out so many advertisements from them!). Surely, this is a dubious approach to promotion.
Dementia in twins SiR-Christensen
and
colleagues (April 6, p 976),1 article,2 reported their analysis of the Danish Twin Register concerning the incidence of Alzheimer’s disease (AD) in mono- and dizygotic-twin individuals. They did not find a difference in the incidence between these groups of individuals comparable to that found in our own study. The major difficulty in investigating dementia by the record linkage method arises from inadequate clinical responding
to
our
classification of dementia in the 1970s, and even in the 1980s. Diagnoses of morbus cerebrovascularis ischaemicus generalisatus (International Classification of Diseases code 437) and arteriosclerosis universalis (440.99) were commonly used as the synonyms for AD. Conversely, our review of medical records showed that the diagnosis of dementia senilis (290) included, in addition, many cases of vascular dementia. This inclusion is understandable since the entity of vascular dementia, in its presently understood form, was only established in clinical practice by the late 1980s. In nearly 35% of the cases classified in the review as having either AD or vascular dementia, the initial classification was insufficient or incorrect. Therefore we consider that validation of the diagnosis is necessary when the incidence of
1706
*Robert Booy, Hermione Lyall *Department of Epidemiology, Institute of Child Health, London WC1 1EH and Department of Paediatrics, Imperial College School of Medicine at St Mary’s, London W2 1NY, UK
Retraction: Polymorphism at the tumour necrosis factor locus: a marker of genetic predisposition to colorectal cancer? SIR-Our recent attempts to replicate these experiments’1 have been unsuccessful. We have since discovered that the data were affected by a technical error and cannot now be sustained. The nature of the error was such that we were unable to correctly discriminate between adjacent alleles and this led to the artifactual accumulation of "allele 3" in the colorectal cancer group. We therefore withdraw these data. *D A Campbell, M Field, C S McArdle, T G Cooke, G Gallagher *University of Leeds Department of Molecular Medicine, Queen Elizabeth Building, Glasgow Royal Infirmary, Glasgow G31 2ER, UK; University of Glasgow Department of Medicine; University of Edinburgh Department of Surgery. University of Glasgow Department of Surgery 1
Campbell DA, Field M, McArdle CS, Cooke TG, Gallagher G. Polymorphism at the tumour necrosis factor locus: a marker of genetic predisposition to colorectal cancer? Lancet 1994; 343: 293-94.
rats
showed that
some rats
R Friedman, Georgia Malcolm, José G Rigau-Pérez, Primo Arámbulo III, Robert V Tauxe *Foodborne and Diarrheal Diseases Branch, DBMD, Dengue Branch, DVBID, NCID, Centers for Disease Control and Prevention, Atlanta GA 30333, USA; and Veterinary Public Health Program, Pan American Health Organization/World Health Organization, Washington DC
*Cindy
1 2 3
Rosenau MJ. The inefficiency of bacterial viruses in the extermination of rats. Public Health Bull 1910; 40: 179-204. Taylor J. Bacterial rodenticides and infection with Salmonella enteritidis. Lancet 1956; i: 630-34. Mishu B, Griffin PM, Tauxe RV, et al. Salmonella enteritidis gastroenteritis transmitted by intact chicken eggs. Ann Intern Med
1991; 115: 190-94. 4
5
Henzler DJ, Opitz HM. The role of mice in the epizootiology of Salmonella enteritidis infection on chicken layer farms. Avian Dis 1992; 36: 625-31. Anonymous Joint FAO/WHO expert committee on zoonoses. World Health Organ Tech Rep Ser 1967; 378: 1-127
various types of dementia is evaluated retrospectively. In our study, the linkage of the registers according to the first diagnosis yielded the monozygotic/dizygotic ratio 1.2. When the linkage was done with four diagnoses, the ratio was 1.5. After review and adjustment for age, the ratio climbed to 1.8. Another point is that the linkage of registers yielded only a few twin pairs concordant for ICD code 290 (senile dementia) and the most concordant co-twins were not found until the validation of diagnosis. Dementia in a co-twin had been recorded in hospital notes but a diagnosis of dementia was not concluded at the discharge. In the analysis of Danish twins, the frequency of concordant pairs was not stated. This would have been of interest in comparing the two data sets. *I
Räihä, J Kaprio, M Koskenvuo, T Rajala, L Sourander
Departments of *Geriatrics and Public Health, University of Turku, 20700 Turku, Finland; and Department of Public Health, University of Helsinki Christensen K, Holm NV, Vaupel JW. Lancet 1996; 347: 976. Räihä I, Kaprio J, Koskenvuo M, Rajala T, Sourander L. Alzheimer’s disease in Finnish twins. Lancet 1996; 347: 573-77.
1 2
Will
today
be the
day YOU hear from "J"?
SiR-Drowning in medical reading? Can’t even keep up with all the junk mail? Maybe you, too, have lately received an advertisement ripped out of an un-named medical journal, with a "post-it" attached from "J" saying: "Try this. It’s really good!". The advertisement extols the benefits of American Medical Digest, a journal summarising reports in 150 other medical journals, which can be subscribed to for a year at the introductory rate of$195. The impression is created that a benevolent friend in the USA has thoughtfully torn out the article, attached the "post-it", and written to you, a busy academic, with some good advice on how to "stay completely informed-despite your tight schedule". The ruse is uncovered (or is it?) upon the realisation that one does not know a "J" in the USA; "J" has not put his/her address on the envelope-and further inquiries quickly locate other colleagues who have received the same apparently personal letter from "J" (who must subscribe to a ton of journals in order to rip out so many advertisements from them!). Surely, this is a dubious approach to promotion.
Dementia in twins SiR-Christensen
and
colleagues (April 6, p 976),1 article,2 reported their analysis of the Danish Twin Register concerning the incidence of Alzheimer’s disease (AD) in mono- and dizygotic-twin individuals. They did not find a difference in the incidence between these groups of individuals comparable to that found in our own study. The major difficulty in investigating dementia by the record linkage method arises from inadequate clinical responding
to
our
classification of dementia in the 1970s, and even in the 1980s. Diagnoses of morbus cerebrovascularis ischaemicus generalisatus (International Classification of Diseases code 437) and arteriosclerosis universalis (440.99) were commonly used as the synonyms for AD. Conversely, our review of medical records showed that the diagnosis of dementia senilis (290) included, in addition, many cases of vascular dementia. This inclusion is understandable since the entity of vascular dementia, in its presently understood form, was only established in clinical practice by the late 1980s. In nearly 35% of the cases classified in the review as having either AD or vascular dementia, the initial classification was insufficient or incorrect. Therefore we consider that validation of the diagnosis is necessary when the incidence of
1706
*Robert Booy, Hermione Lyall *Department of Epidemiology, Institute of Child Health, London WC1 1EH and Department of Paediatrics, Imperial College School of Medicine at St Mary’s, London W2 1NY, UK
Retraction: Polymorphism at the tumour necrosis factor locus: a marker of genetic predisposition to colorectal cancer? SIR-Our recent attempts to replicate these experiments’1 have been unsuccessful. We have since discovered that the data were affected by a technical error and cannot now be sustained. The nature of the error was such that we were unable to correctly discriminate between adjacent alleles and this led to the artifactual accumulation of "allele 3" in the colorectal cancer group. We therefore withdraw these data. *D A Campbell, M Field, C S McArdle, T G Cooke, G Gallagher *University of Leeds Department of Molecular Medicine, Queen Elizabeth Building, Glasgow Royal Infirmary, Glasgow G31 2ER, UK; University of Glasgow Department of Medicine; University of Edinburgh Department of Surgery. University of Glasgow Department of Surgery 1
Campbell DA, Field M, McArdle CS, Cooke TG, Gallagher G. Polymorphism at the tumour necrosis factor locus: a marker of genetic predisposition to colorectal cancer? Lancet 1994; 343: 293-94.