In a case-control study 82 patients with Crohn's disease and matched controls drawn from general practice lists were questioned about their smoking habits. Patients with Crohn's disease were significantly more likely to be smokers than the controls, and the association was stronger for smoking habit before the onset of the disease than for current smoking habit, the relative risks for smokers compared with non-smokers being 4-8 and 3-5 respectively.Taken in conjunction with earlier data showing an association between non-smoking and ulcerative colitis, these results suggest that smoking habit may be an important determinant of the type of inflammatory bowel disease that develops in predisposed subjects.
In several patients the findings that metastases were forming in some organs but not others, despite infusion of viable tumour cells into the systemic circulation, provides direct evidence supporting the "seed and soil" hypothesis of Paget." This proposes that although haematogenously released tumour cells (seeds) "are carried in all directions they can only live and grow" if they lodge in an organ (soil) that is congenial. The clearest demonstration of this was in the patient (case 12) who was known before insertion of the shunt to have large haematogenous deposits in the liver and bone marrow but in whom there were no metastases or even tumour cells in the lungs or elsewhere at necropsy. With knowledge of such unusual patterns of spread and availability of tumour cells from the same patients it is possible to investigate the host factors responsible for local encouragement or suppression of metastatic growth; these are now being studied in this laboratory. A further point in relation to host related factors is that no cellular immune response was seen in response to micrometastases or isolated tumour cells. Also no features suggesting regression of tumour deposits-for example, dying tumour cells or host lymphoid infiltration-were seen even in those patients who survived for only short periods. It seems unlikely, therefore, that failure to form metastases is due to surveillance by the immune system.In conclusion, our observations provide otherwise unobtainable information on mechanisms of metastasis in man and confirm that peritoneovenous shunting for malignant ascites does not carry the hazard of promoting clinically important metastasis. This study was supported by the Cancer Research Campaign ofGreat Britain, whose help we gratefully acknowledge. We also thank Mrs P Messer and Mrs B Carter for help in coordinating this study and in preparing the manuscript, and our clinical colleagues for referring cases for treatment. References
SUMMARY Previous studies have consistently found strong positive associations between refined sugar intake and Crohn's disease (CD) and recently between smoking and CD. As refined sugar intake and smoking are themselves associated we have enquired about smoking and added sugar intake (AS) and smoking in CD using a postal questionnaire sent to 104 CD patients and 153 community controls. Smoking and AS were associated with one another. After adjusting for AS, smoking showed a significant association with CD with a relative risk of 1.8. After adjusting for smoking habit, AS was also strongly associated with CD in never and exsmokers and in a dose response pattern, with the relative risks for no AS, <50 g/day and >50 g/day being respectively 1.0, 1.8, and 4-6 (X2=12-1; p<0005). No association between CD and AS was evident in smokers. The AS relationship was supported by a separate association between frequency of confectionery consutnption and CD. These findings indicate that while smoking and AS are individually associated with CD combined exposure results in no further increase in risk, suggesting that they may operate through a common mechanism. Increased refined sugar consumption by patients withCrohn's disease (CD) was first reported by Martini and Brandes in 1976 and has since been demonstrated in many studies, although some have suggested that the increased consumption is secondary to the development of CD.'-9 We, and subsequently others, have recently found a strong association between smoking and CD which antedates disease onset."''5 Smoking has previously been found to be positively associated with sugar consumption.'6`7 It therefore seemed possible that the association of smoking or sugar consumption with CD might be due to confounding, that is, any increase in smoking, or sugar consumption, in CD patients might be accounted for by the one habit being associated with the other. We have therefore reapproached subjects from our earlier study with a second questionnaire designed to determine whether the association of smoking and CD was related to increased sugar consumption by smokers with CD.
To determine whether the social class differences in duodenal ulcer frequency may be explained by differences in physical activity at work, the energy expenditure during work, smoking habits, and social class were compared in 76 recently diagnosed duodenal ulcer patients and in age and sex matched community controls. As anticipated, the relative risk of duodenal ulcer showed significant associations with smoking and social class. Social class and physical activity at work were associated with one another. After adjusting for age, sex, smoking, and social class, physically active work was still associated with duodenal ulcer, with relative risks for moderate and high activity compared with sedentary work being 1*3 (0.6-3.0) and 3*6 (1.3-7.8) respectively. Within each social class stratum, the relative risk of having a duodenal ulcer was greater in those with a high level of occupational activity than in those undertaking sedentary work.
An association between duodenal ulceration and a low fibre intake and a high refined carbohydrate diet has been reported. We therefore compared the current diet, smoking habits, social class, and possible other risk factors of 78 patients with duodenal ulcer and a community control group matched for age and sex. Logistic regression for matched sets was used to calculate the relative risks for successive quintiles of dietary fibre and sugar intake before and after adjustment for total calorie intake and for the possible confounding effect of other known risk factors. Relative risks did not differ materially or consistently for total dietary fibre or for the cereal moiety whether adjusted or not for calorie intake. By contrast, relative risks tended to be reduced with high vegetable fibre intake and with low refined sugar intake. After controlling for smoking and social class, both of which were associated with ulcer disease, and for relative weight (Quetelet's index), the relation between ulcer disease and low refined sugar intake persisted, while that with high vegetable fibre intake was reduced. The results of this study indicate that a lack of cereal or total fibre intake plays no part in duodenal ulcer development but that a low refined sugar intake may be a protective factor.
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