LETTERS TO THE EDITOR “Cot death” rates on diVerent days of the week EDITOR,—The series of reprints that have arisen from the New Zealand cot death study, which took place around 1990, such as the article by Williams and colleagues 1 are repli- cating work that we carried out in SheYeld in the l950s. 2–4 In the SheYeld studies, as well as noting the significance of prone sleeping, we also saw an increase in children presenting as unexpected deaths at the weekend. In addi- tion, we found a relative increase on the night after the day when family doctors took their traditional half day oV and did not hold after- noon or evening surgeries. This feature became most apparent when the cot death rates were seen as part of the total pattern of deaths—that is, a diminution in acute deaths following admission to hospital was replaced by greater numbers of home cot deaths. This pattern of deaths in SheYeld changed after we introduced the prevention pro- gramme identifying children at increased risk of unexpected death. 5 We found that we had largely eliminated the partially explained group of cot deaths, and the total infant and cot death rates in the city fell considerably. The point that needs to be made is that such sociopathological studies on child deaths should always be carried out in relation to the pattern and site of deaths, and to the total infant death rate in the local com- munity. Much of the confusion related to risk discriminants results from the false assump- tion that with cot deaths one is dealing with a single cause. Particular causes can be in- creased, reduced, or eliminated. This has been particularly striking during the past 50 years relating to what are almost certainly accidental suVocation deaths. An increase in the unexpected death rate occurred following propaganda arising from neonatologists rec- ommending prone sleeping in children. The recent complete reversal of that policy seems to have resulted in the elimination of that group and hence the fall in “cot death” rates to their original level. JOHN L EMERY Emeritus Professor of Paediatric Pathology, Room C1, Department of Paediatrics Stephenson Unit, University of SheYeld, The Children’s Hospital Western Bank, SheYeld S10 2TH, UK 1 Williams SM, Mitchell EA, Scragg R, and the New Zealand National Cot Death Study Group. Why is sudden infant death syndrome more common at weekends? Arch Dis Child 1997;77:415–19. 2 Emery JL. Epidemiology of sudden unexpected or rapid deaths in children. BMJ 1959;ii: 925–8. 3 Emery JL. Sudden and unexpected death in infant [abridged]. Proceedings of the Royal Society of Medicine 1959;52:890 [Section of paediatrics, pp 32–4.] 4 Emery JL, Crowley EM. Clinical histories in cases of sudden death in infants reported to the Coroner. BMJ 1956;ii:1578. 5 Carpenter RG, Gardner A, Jepson M, et al. Pre- vention of unexpected infant death. Evaluation of the first seven years of the SheYeld intervention programme. Lancet 1983;i:723–7. Nitrate and nitrite content of meat products EDITOR,—Having read the case report by Kennedy and colleagues, 1 we would like to point out some aspects of the production of dry fermented sausage, salami, and sausage. We agree with Kennedy et al that food manu- facturers should order ingredients specifi- cally, in writing, and preferably by their approved chemical name. Nitrate and nitrite are widely used as addi- tives in meat products for eVects such as red- dening, as preservatives, and as antioxidants. Prolonged ingestion of nitrates and nitrites may cause methaemoglobinaemia and favour the formation of carcinogenic nitrosamines. 23 The use of nitrates and nitrites as meat curing agents is restricted in Turkey by the Regula- tions of food additives, 4 but it does not prevent the use of overdose by food processors as the residual quantities in the end products are not limited. To investigate nitrate and nitrite contents in meat products for human consumption we collected 65 dry fermented sausages, 83 salamis, and 60 sausage samples from mar- kets in Istanbul and analysed them with spec- trophotometric methods. 5 The average ni- trate concentrations were 87.0 mg/kg (range 0–362.9) in dry fermented sausage, 102.4 mg/kg (0–390) in salami, and 147.4 mg/kg (0–370.9) in sausage. The average nitrite concentrations were 42.8 mg/kg (0376.9) in dry fermented sausage, 87.6 mg/kg (0–375) in salami, and 102.8 mg/kg (0–420) in sausage. The nitrate contents in 3.6% of salamis and 11.7% of sausages were above 300 mg/kg. The nitrite contents in 3.0% of dry fermented sausages, 15.6% of salamis, and 20% of sausages were above 150 mg/kg. Therefore, nitrates and nitrites used during the production of meat products were higher than the concentrations indicated by the Regulations of food additives and this might be detrimental to human health. Therefore, the concentrations of nitrate and nitrite in the end product should be limited and control- led. SUZAN YALÇIN Department of Food Hygiene and Technology, Faculty of Veterinary Medicine, Selçuk University, Konya, Turkey S SONGÜL YALÇIN Department of Social Pediatrics, Institute of Child Health, Hacettepe University, Ankara, Turkey 1 Kennedy N, Smith CP, McWhinney P. Faulty sausage production causing methaemoglobi- naemia. Arch Dis Child 1997;76:367–8. 2 Hotchkiss JH, Cassens RG. Nitrate, nitrite and nitroso compounds in foods. Food Technology in Australia 1988;40:100–5. 3 Vösgen W. Curing. Are nitrite and nitrate neces- sary or superfluous as curing substances? Fleischwirtsch 1992;72:1675–8. 4 Regulations of Turkish food codex. The oYcial news of the Turkish Republic [Turkish], 1997;No 23172:44. 5 Yalçin S, Güneg ˘i S, Yalçin SS. Nitrate and nitrite levels of dry fermented sausage, salami and sausage consumed in Istanbul [abstract; in Turkish]. I. National congress of environmen- tal health, Ankara, Turkey, December 1997. Incidence of coeliac disease EDITOR,—We were interested to read the arti- cle by Challacombe et al reported a declining incidence of coeliac disease in West Somerset. 1 Our observations on the incidence of coeliac disease in South Glamorgan over a 15 year period have revealed no such decline. We determined the frequency of new cases of coeliac disease from 1981 to 1995 in patients resident in South Glamorgan (1995 total population 415 900; population 14 years or younger 83 500; total live births 5700 per year). Cases of coeliac disease were ascer- tained from hospital activity data, pathology, dermatology, and dietetic records, general practitioner lists, and the local coeliac society. All cases satisfied the revised ESPGAN diagnostic criteria. 2 Over the three five-year periods (1981–85, 1986–90, 1991–95) the number of new cases in children younger than 14 were 8, 10, and 9, respectively— annual incidences of 2.08, 2.53, and 2.15 per 100 000. The incidence of childhood coeliac disease has therefore remained constant over the 15 year period at approximately 1 in 2500 to 1 in 3000 live births. In contrast, the inci- dence of adult coeliac disease has increased over the three time periods from 1.3 to 2.15 and 3.08 per 100 000. The incidence of adult dermatitis herpetiformis has remained be- tween 0.3 and 0.43 per 100 000. The age at diagnosis of children with coeliac disease has risen from a median of 4 years (1 to 10) between the period 1981 to 1990, to 7.6 years (1.7 to 14.9) between 1991 and 1995, whereas the age at presentation of adult patients has remained constant with a median of 49.5 years (19 to 88). From 1981–90 the predominant presenting symp- toms were gastrointestinal, with 70% of the children having diarrhoea, and only three of the 18 children being anaemic. Between 1991–95 anaemia associated with vague abdominal symptoms (such as discomfort or bloating) became a more common presenta- tion (44%) and diarrhoea was noted in only 11%. Anaemia as the sole presenting feature remained rare at diagnosis (one of 27) compared with a figure of 25% of the adult coeliac population over the 15 year period. Two asymptomatic children were diagnosed following screening for IgA antigliadin anti- bodies in siblings of aVected probands. We may be missing asymptomatic cases or those that present later with symptoms such as anaemia, so the true incidence is likely to be much higher. Many adult cases are now identified from duodenal biopsies taken dur- ing upper gastrointestinal endoscopy for investigation of iron deficiency anaemia and non-specific gastrointestinal symptoms. The incidence of adult dermatitis herpetiformis, which shares the same genetic basis as coeliac disease, 3 has remained stable, suggesting the increased diagnosis of adult coeliac disease primarily because of increased clinical aware- ness. We consider that although the classic gastrointestinal presentation of coeliac dis- ease may be decreasing in children, the over- all incidence may not have altered, and is likely to be much higher than previously rec- ognised once screening tests become more widely employed. It is thus vital that we remain aware of the diagnosis and how subtle its presentation may be, and screen actively for cases using IgA antigliadin antibody and antiendomysial antibody, particularly in populations at higher risk (for example, fam- ily history, Down’s syndrome, insulin de- pendent diabetes mellitus). HUW R JENKINS Consultant Paediatric Gastroenterologist NEIL HAWKES Registrar in Gastroenterology Arch Dis Child 1998;79:198–204 198