Pediatric inflammatory bowel disease in southeastern Norway: a five-year follow-up study

OBJECTIVES: Few prospective population-based studies have been carried out on the incidence of inflammatory bowel disease (IBD). In a population-based study of pediatric IBD in southeastern Norway, patients <16 years at the time of diagnosis were followed up prospectively. The study reports on changes in diagnosis and clinical outcome 5 years after diagnosis. METHODS: From 1990 to 1993 new cases of IBD were registered in a population of 174,482 children aged less than 16 years. The patients' diagnoses were systematically evaluated 1 year after diagnosis and the patients were followed up clinically for up to 5 years after diagnosis. Results: Sixteen cases of Crohn's disease (CD), 14 cases of ulcerative colitis (UC) and 3 cases of indeterminate colitis (IND) were initially registered. After 1 year IND were reclassified as UC (n=2) or CD (n=1). Altogether, 18% (6/33) had their diagnosis changed during the 5 years of follow-up, which yielded a mean annual incidence of 2.7/100,000 for CD and 2.0/100,000 for UC. Of the children with CD, more than 80% had relapses during the 5-year period, and 6 of 18 had surgery. Two-thirds of the children with UC had relapses during the 5-year period, and 3 patients underwent colectomy. CONCLUSIONS: An incidence of 4.7/100,000 is comparable to that found in most other studies made in Europe. The relationship between UC and CD in children was found to differ from that in the adult population. One of 5 patients had their diagnosis changed during the follow-up period. Pediatric UC seems to have a more serious course of disease than in the adult IBD population, which may be explained by the higher risk of pancolitis at diagnosis.     

Incidence of inflammatory bowel disease in Primorsko-goranska County, Croatia, 2000-2004: A prospective population-based study

OBJECTIVE: It has been suggested that the incidence of inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD), is higher in northern than in southern Europe. Recent epidemiological studies showed the loss of the previously described geographical north-south gradient. The aim of this study was to investigate the incidence of UC and CD in Primorsko-goranska County, Croatia. MATERIAL AND METHODS: In the period 1 January 2000 to 31 December 2004 (5 years) all new patients diagnosed with IBD were prospectively identified according to a standard protocol for case ascertainment and definition. A total of 178 residents (81 F, 97 M) were newly diagnosed as having IBD during the study period. Of these, 70 had UC and 100 CD. Eight patients had indeterminate IBD. The data on patients were collected using a data form completed by gastroenterologists. RESULTS: Annual age-standardized incidence rates were 4.3/10(5) (95% CI 2.6-6.0) for UC and 7.0/10(5) (95% CI 3.4-10.6) for CD. The highest incidence rate was observed in the age group 35-44 years for UC and the 25-34 years age group for CD. The incidence of IBD was higher in the urban than in the rural population, with the exception of on the islands. CONCLUSIONS: The incidence of IBD was higher than previously observed in Croatia. Our results suggest that CD incidence rates in the northern coastal part of Croatia are currently comparable with those reported in northern Europe.     

Mortality in inflammatory bowel disease: a population-based cohort study

BACKGROUND & AIMS: There is no consensus regarding any increase in mortality with inflammatory bowel disease (IBD). In general, previous studies were not contemporary and were unable to correct for likely confounders. We have performed a large cohort study to examine contemporary IBD related mortality in the United Kingdom. METHODS: We selected subjects within the General Practice Research Database with a coded diagnosis of inflammatory bowel disease and up to 5 matched controls for each. We derived the date of recorded deaths and information on smoking and a variety of medical conditions. We calculated both the absolute risk of death and the relative risk as a hazard ratio corrected for available confounders by Cox regression. RESULTS: We included 16,550 IBD cases with 1047 deaths and 82,917 controls with 3758 deaths. The mortality rate was 17.1 per 1000 person-years overall for IBD cases and 12.3 for controls; this difference was greatest in the elderly. Conversion of these figures to hazard ratios by Cox regression gave hazard ratios of 1.54 (1.44-1.65) for all IBD, 1.44 (1.31-1.58) for ulcerative colitis (UC), and 1.73 (1.54-1.96) for Crohn's disease. The greatest hazard ratio for UC was among the 40-59-year age group (1.79 [1.42-2.27]) and for Crohn's disease among 20-39-year-olds (3.82 [2.17-6.75]). CONCLUSIONS: IBD is associated with an overall small increase in mortality rate greatest in relative terms in younger subjects but in absolute terms in the elderly.     

Incidence of inflammatory bowel disease in northern France (1988-1990).

There were no data concerning the incidence of inflammatory bowel disease (IBD) in France. The aim of this study was to investigate the incidence of Crohn''s disease and ulcerative colitis in northern France. This prospective population based study was realised through the gastroenterologists of the region Nord-Pas de Calais and the Somme Department. Each gastroenterologist referred patients consulting for the first time with clinical symptoms compatible with IBD. Data were collected by an interviewer practitioner present at the gastroenterologist''s consulting room. Two independent expert gastroenterologists assessed each case in a blind manner and made a final diagnosis of Crohn''s disease, ulcerative colitis, ulcerative proctitis, or unclassifiable chronic colitis. From 1988 to 1990, 1291 cases of IBD were recorded: 674 (52%) Crohn''s disease, 466 (36%) ulcerative colitis including 162 proctitis (35%), and 151 (12%) unclassifiable chronic colitis. The mean annual incidence was 4.9 per 100,000 for Crohn''s disease and 3.2 for ulcerative colitis. The sex ratio F/M was 1.3 for Crohn''s disease and 0.8 for ulcerative colitis. The highest age specific incidence rate for Crohn''s disease was between 20 and 29 years: 13.1 for women and 9.8 for men. The highest age specific incidence rate for ulcerative colitis was between 20 and 39 years: 5.5 for women and 6.5 for men. This first French prospective study has shown an incidence rate for Crohn''s disease comparable with that seen in north European studies but lower than that seen for ulcerative colitis. These results could be related to the different environmental factors or the genetic background of the population studied, or both.     

Bone mineral density in patients with inflammatory bowel disease: a population-based prospective two-year follow-up study

BACKGROUND: Bone loss and osteoporosis are commonly reported in inflammatory bowel disease (IBD), especially Crohn disease (CD). The aims of the present study were to evaluate changes in bone mineral density (BMD) in IBD patients during a 2-year follow-up period, and to investigate the role played by possible contributing factors in bone loss. METHODS: Sixty patients with CD and 60 with ulcerative colitis (UC) were studied initially. Fifty-five CD and 43 UC patients were re-examined after 1 year, and 50 CD and 44 UC patients after 2 years. Lumbar spine, femoral neck and total body BMD were measured by dual X-ray absorptiometry (DXA), and Z scores were obtained by comparison with age-matched and sex-matched healthy subjects. Biochemical variables were assessed at inclusion and at the 1-year follow-up visit. RESULTS: Mean BMD values were unchanged in both CD and UC patients. In patients with repeated measurements, significant differences in Z scores (delta Z score) were found for femoral neck and total body in CD and for total body in UC. Significant bone loss occurred in 11 CD (22%) and 12 UC (27%) patients. A significant increase in BMD was found in 21 CD (42%) and 20 UC (46%) patients. In CD patients the initial BMD values for lumbar spine and femoral neck were inversely correlated to BMD changes at the same sites and the change in body mass index (BMI) was positively correlated to change in the total body BMD. C-reactive protein was significantly higher in CD patients with bone loss. Biochemical markers of bone metabolism could not be used to predict BMD changes. Although it was not significant, there was a relationship between corticosteroid therapy and bone loss in CD. CONCLUSIONS: Only minor changes in BMD were observed in both CD and UC patients during a 2-year period. The multifactorial pathogenesis of bone loss in IBD makes it difficult to assess the importance of each single contributing factor. However, our results indicate that disease activity and corticosteriod therapy are involved in bone loss in CD patients.     

Pulmonary manifestations in inflammatory bowel disease: a prospective study

Background

Although pulmonary abnormalities have been recognized in patients with inflammatory bowel diseases (IBD), their prevalence and clinical significance are not known.

Aim

To study the prevalence and clinical significance of pulmonary abnormalities in patients with IBD.

Methods

Ninety-five non-consecutive patients with IBD (12 Crohn’s disease, 83 ulcerative colitis; mean age 41.9 [SD 13] years; 47 women) were prospectively studied from January 2007 to March 2010. Pulmonary function tests (PFT) and high-resolution CT (HRCT) chest were performed in them. PFT were compared to those in 270 healthy (control) subjects matched for age, sex and smoking status.

Results

Twenty-seven (28.5%) patients and 11 (4%) control subjects had abnormal PFT (p?Conclusion PFT and HRCT chest showed abnormality in about one-quarter of patients with IBD. A majority of patients with these abnormalities were asymptomatic.     

The incidence of inflammatory bowel disease in a rural region of Southern Germany: a prospective population-based study

OBJECTIVE: Although important advances in understanding the aetiology and pathogenesis of inflammatory bowel disease (IBD) have been made, many questions remain unanswered. As the most recent data available on the incidence of IBD in Germany were collected about 15 years ago, we set up a new population-based cohort to determine current incidence data for a defined region in Germany and to establish a basic cohort for prospective follow-up. METHODS: All patients living in the region of Oberpfalz newly diagnosed with IBD between 1 January 2004 and 31 December 2006 were included in this study by setting up a network of reporting clinicians and general practitioners in hospitals as well as in private practices. Demographic and clinical characteristics such as age at first diagnosis, localization of the disease, extraintestinal manifestations or family history on IBD were documented. Age-adjusted incidence rates are presented with 95% Poisson confidence intervals (CIs), based on the European standard population. RESULTS: In total, 286 newly diagnosed patients with IBD were reported in this region, 168 patients suffering from Crohn's disease (CD), 105 patients with ulcerative colitis. Age-standardized incidence rates were 11.0/10(5) (95% CI: 9.1-11.6) for IBD, 6.6/10(5) (95% CI: 5.6-7.7) for CD and 3.9/10(5) (95% CI: 3.2-4.7) for ulcerative colitis. Peak incidences were found in the age interval of 16-24 years for both diseases, predominantly for CD. Age at first diagnosis was lower, extraintestinal manifestations and a positive family history on IBD were more common in patients with CD. CONCLUSION: The incidence rate in IBD seems to be stable in Germany as compared with previously reported data, as is the remarkable predominance of CD. Prospective follow-up studies will be based on this incidence cohort.     

Childhood growth and risk of inflammatory bowel disease: a population-based study of 317,030 children

Background: Growth in childhood is associated with later development of autoimmune diseases and cancer, but the impact of growth on risk of inflammatory bowel disease (IBD) remains unknown. We conducted a population-based cohort study to examine whether birth weight, childhood height, or changes in height associated with later risk of IBD.

Methods: Our cohort consisted of 317,030 children from the Copenhagen School Health Records Register (born 1930–1989) with height repeatedly measured from age 7 to 13 and with data on birth weight on a subset. Through linkage to the Danish National Patients Register, cases of IBD were identified. Cox proportional hazard regression was used to examine associations between measures of childhood growth and risk of IBD.

Results: During more than 9 million years of follow-up, 1612 individuals were diagnosed with Crohn’s disease (CD) and 2,640 with ulcerative colitis (UC). Birth weight and childhood heights were not associated with subsequent risk of CD or UC (HRs close to 1.00). Childhood growth from 7 to 10 years (CD: HR, 1.00; 95% CI, 0.85–1.18; UC: HR, 0.92; 95% CI, 0.81–1.05) and 10 to 13 years (CD: HR, 1.02; 95% CI, 0.89–1.17; UC: HR, 0.95; 0.85–1.05) did not associate with risk of IBD either.

Conclusion: In this large population-based cohort study, birth weight and childhood growth did not influence risk of IBD, which contrasts with observations in other chronic diseases. Thereby, the study also suggests that pre-clinical effects of adult IBD are not measurable in childhood and that childhood risk factors for IBD do not influence growth.     

Incidence of inflammatory bowel disease in Finnish children, 1987-2003

BACKGROUND: The incidence of inflammatory bowel disease (IBD) has been increasing in Western countries. In younger people, Crohn's disease (CD) predominates over ulcerative colitis (UC), but the finding is not universal. The present study aimed to characterize not only the incidence but also the clinical picture of IBD from 1987 to 2003 in a large pediatric population in Finland. MATERIALS AND METHODS: Data were collected from the patient discharge and medical records at the 2 largest university hospitals in Finland. The study population covered a total of 619,340 children, representing 56% of the children <18 years old in the country. All of the cases diagnosed with IBD from 1987 to 2003 were reviewed. Clinical, endoscopic, and histological data were collected. Incidence rates were estimated based on statistical assumptions. RESULTS: A total of 604 cases with IBD were diagnosed during the 17-year period. All of the patients had undergone endoscopy. The diagnosis was CD in 203 (34%) cases, UC in 317 (52%) cases, and indeterminate colitis (IC) in 83 (14%) cases. The mean annual incidence rate increased from 3.9/100,000 (95% confidence interval [CI] 2.5-5.8) in 1987 to 7.0/100,000 (CI 5.0-9.4) in 2003 (P < 0.001). The majority of cases were 12 to <15 years old (n = 200, 33%). Of the patients, 5.1% were <3 years old and 14% were <6 years old. IC was most common in young children; 29% of all IBD patients <3 years of age had IC. Of the patients, 97% had been followed up until the age 18 in the hospitals after initial diagnosis (median follow-up 3.1 years). Of the patients, 45.2% were initially treated with steroids, whereas 17.8% received immunosuppressive agents at the end of the follow-up. Operations had been performed in 21% of the cases before age 18. The median time interval from the diagnosis to the first operation was 1.8 (range 7.8) years. CONCLUSIONS: The incidence of pediatric IBD almost doubled in Finland from 1987 to 2003. Surgical intervention was common early in the disease course.     

The epidemiology of inflammatory bowel disease in Canada: a population-based study

BACKGROUND: Previously, we have demonstrated a high incidence and prevalence of Crohn's disease (CD) and ulcerative colitis (UC) in the Canadian province of Manitoba. However, the epidemiology of inflammatory bowel disease (IBD) in other regions of Canada has not been defined. The aim of this study was to estimate the incidence and prevalence of CD and UC in diverse regions of Canada and the overall burden of IBD in Canada. METHODS: We applied a common case identification algorithm, previously validated in Manitoba to the provincial health databases in British Columbia (BC), Alberta (AB), Saskatchewan (SK), Manitoba (MB), and Nova Scotia (NS) to determine the age-adjusted incidence rates per 100,000 person-years for 1998-2000 and prevalence per 100,000 for mid 2000 and to estimate the IBD burden in Canada. Poisson regression was used to assess differences in incidence rates and prevalence by gender, age, and province. RESULTS: The incidence rate for CD ranged from 8.8 (BC) to 20.2 (NS), and for UC ranged from 9.9 (BC) to 19.5 (NS). The prevalence of CD was approximately 15- to 20-fold higher than the incidence rate, ranging from 161 (BC) to 319 (NS). This was similar for the prevalence of UC, which ranged from 162 (BC) to 249 (MB). Adjusting for age and province, the female:male ratio for incidence ratio was 1.31 (p < 0.0001) for CD and 1.02 (n.s.) for UC and was mostly stable across the five provinces. CONCLUSIONS: Approximately 0.5% of the Canadian population has IBD. Canada has the highest incidence and prevalence of CD yet reported.     

Body composition in patients with inflammatory bowel disease: a population-based study

OBJECTIVE: Weight loss and nutritional depletion are common features of inflammatory bowel disease. Our aim was to assess body composition in patients with Crohn's disease (CD) and ulcerative colitis (UC) and to evaluate possible differences between the patient groups and healthy subjects. METHODS: A total of 60 patients with CD, 60 patients with UC, and 60 healthy subjects were investigated. Each group consisted of 24 men and 36 women. Body composition was measured by dual x-ray absorptiometry and Z scores were obtained by comparison to age- and sex-matched normal values. RESULTS: Bone mineral content and lean body mass were significantly lower in patients with CD compared with patients with UC and healthy subjects. The body composition of CD men was more strongly affected than that of women. UC patients had significantly higher fat mass and body mass index than patients with CD and healthy subjects. There was no difference in the percentage of fat mass between the two patient groups. Corticosteroid treatment and smoking had a negative impact on bone mineral content and lean body mass in CD patients independently of each other. CONCLUSIONS: CD was associated with disturbances in body composition: both bone mineral content and lean body mass were significantly reduced, especially in men with CD. Corticosteroid therapy and smoking had a significant influence on body composition in patients with CD. When studying the effects of inflammatory bowel disease on body composition and nutritional status, patients with CD and UC should be evaluated separately.     

The clustering of other chronic inflammatory diseases in inflammatory bowel disease: a population-based study

BACKGROUND & AIMS: We aimed to discern the relative risk for several chronic inflammatory conditions in patients with ulcerative colitis (UC) and Crohn's disease. METHODS: We used the population-based University of Manitoba IBD Database that includes longitudinal files on all patients from all health system contacts identified by International Classification of Diseases, 9th revision, Clinical Modification codes for visit diagnosis. From the provincial database we extracted a control cohort matching the IBD patients 10:1 by age, sex, and geography. We considered a potential comorbid disease to be present if the patient had 5 or more health system contacts for that diagnosis. The comorbid disease period prevalence was analyzed separately for patients with UC and Crohn's disease and a prevalence ratio was calculated comparing the IBD populations with the matched cohort. RESULTS: There were 8072 cases of IBD from 1984 to 2003, including UC (n = 3879) and Crohn's disease (n = 4193). There was a mean of approximately 16 person-years of coverage for both patients and control patients. Both UC and Crohn's disease patients had a significantly greater likelihood of having arthritis, asthma, bronchitis, psoriasis, and pericarditis than population controls. An increased risk for chronic renal disease and multiple sclerosis was noted in UC but not Crohn's disease patients. The most common nonintestinal comorbidities identified were arthritis and asthma. CONCLUSIONS: The finding of asthma as the most common comorbidity increased in Crohn's disease patients compared with the general population is novel. These may be diseases with common causes or complications of one disease that lead to the presentation with another. Studies such as this should encourage further research into the common triggers in the organ systems that lead to autoimmune diseases.     

Incidence and prognosis of colorectal dysplasia in inflammatory bowel disease: a population-based study from Olmsted County, Minnesota

BACKGROUND AND AIMS: The risk, fate, and ideal management of colorectal dysplasia in inflammatory bowel disease (IBD) remain debated. We estimated the incidence, long-term outcome, and risk factors for progression of colorectal dysplasia (adenomas [adenoma-associated lesions or masses (ALMs)], flat dysplasia, and dysplasia-associated lesions or masses [DALMs]) in a population-based IBD cohort from Olmsted County, Minnesota. MATERIALS AND METHODS: The Rochester Epidemiology Project was used to identify cohort patients with colorectal dysplasia. Medical records were reviewed for demographic and clinical characteristics. Histology slides were reviewed by a pathologist blinded to previous pathology reports. The cumulative incidence of dysplasia was estimated, and the association between patient characteristics and recurrence/progression of dysplasia was assessed using proportional hazards regression. RESULTS: Twenty-nine (4%) IBD patients developed flat dysplasia (n = 8), DALMs (n = 1), ALMs in areas of IBD (n = 18), or ALMs outside areas of IBD (n = 2). Among 6 patients with flat low-grade dysplasia (fLGD) who did not undergo colectomy, none progressed during a median of 17.8 (range 6-21) years of observation with a median of 3 (range 0-12) surveillance colonoscopies. Four (22%) patients with ALMs in areas of IBD who did not undergo surgery developed LGD or DALMs. Primary sclerosing cholangitis and dysplasia located proximal to the splenic flexure were significantly associated with risk for recurrence/progression of dysplasia. CONCLUSIONS: This population-based cohort study from Olmsted County, Minnesota did not confirm an increased risk of cancer related to fLGD, whereas 22% of patients with ALMs in areas of IBD developed fLGD or DALMs.     

The prevalence of extraintestinal diseases in inflammatory bowel disease: a population-based study

OBJECTIVE: The aim of this study was to determine the prevalence of the major extraintestinal manifestations of inflammatory bowel disease (IBD) and their relation to disease diagnosis and gender. METHODS: We used the population-based University of Manitoba IBD Database, which includes longitudinal files on all subjects of all health system contacts identified by International Classification of Diseases, 9th Revision, Clinical Modification codes for visit diagnosis. We extracted a cohort from our database, which included subjects with a known diagnosis of IBD for at least 10 yr. We then determined how many contacts each subject had for each of the following extraintestinal IBD-associated immune diseases: primary sclerosing cholangitis, ankylosing spondylitis, iritis/uveitis, pyoderma gangrenosum, and erythema nodosum. We calculated the prevalence of the extraintestinal diseases using an administrative definition of having at least five health system contacts for the diagnosis in question. This administrative definition has previously been validated in Crohn's disease and ulcerative colitis (UC). RESULTS: A total of 6.2% of patients with IBD had one of six major extraintestinal diseases studied in this report. Only 0.3% of patients had multiple extraintestinal diseases. Iritis/uveitis was the most common extraintestinal disease of all assessed (2.2% of women and 1.1% of men). Iritis/uveitis was more common among women, particularly those with UC (3.8%). Primary sclerosing cholangitis was most common among men with UC (3%). Ankylosing spondylitis was more common among men, and the highest rate was seen among men with Crohn's disease (2.7%). Pyoderma gangrenosum was more common in Crohn's (1.2%) with no gender predilection. Erythema nodosum was similarly present in Crohn's and UC but was more common among women (1.9%). CONCLUSIONS: The associations of immune mediated diseases in extraintestinal sites may help us to further our understanding of IBD pathogenesis, and it may help us in developing a paradigm of disease subsets.     

Incidence of juvenile idiopathic arthritis in children in Estonia: a prospective population-based study

OBJECTIVE: To study the incidence rate of juvenile idiopathic arthritis (JIA) and its clinical subtypes in Estonia, to follow the course of the disease in newly diagnosed patients for 2 years, and to find the frequency of human leucocyte antigens (HLA) B27, DR1 and DR4 in JIA patients. METHOD: A population-based study involving prospective registration of new cases of JIA in 1998-2000 and their clinical follow-up for 2 years. RESULTS: In 1998-2000, 162 new cases of JIA were diagnosed. The mean annual incidence rate of JIA was 21.7 per 100 000 children aged 0-15 years (22.9 in girls and 19.3 in boys). During the investigation period, the incidence rate rose 3.5-fold. Oligoarthritis was the most frequent subtype (mean annual incidence rate of 11.7 per 100 000), followed by seronegative polyarthritis (4.4 per 100 000). HLA-DR1, B27 and DR4 were found respectively in 44.4, 28.6 and 11.1% of cases in which the analysis was performed. In HLA-B27-positive patients, inflammation markers of blood remained at a high level for a longer period compared with HLA-B27-negative patients. CONCLUSIONS: This is the first population-based study on the epidemiology of juvenile arthritis in Estonia in which the new classification criteria defined by the International League of Associations for Rheumatology (ILAR) have been used. In addition to environmental factors, an increase in awareness among family doctors is a probable reason for the rise in incidence during the study period. HLA-B27 might have predictive value as a marker of chronicity of inflammation.     

Inflammatory bowel disease in Iceland, 1990-1994: a prospective, nationwide, epidemiological study

BACKGROUND: Two separate nationwide, retrospective epidemiological studies of inflammatory bowel disease (IBD) in Iceland over a combined 40-year period, 1950-1989, have shown a continually rising incidence. The main objective of this study was to investigate the incidence of IBD prospectively for the 5-year period 1990-1994 to determine whether there still was an ongoing increase. METHODS: The retrieval of new cases of ulcerative colitis (UC) and Crohn's disease (CD) was based on a monthly review of all small and large intestinal tissue specimens with any type of inflammation submitted to all three departments of pathology in Iceland. All small intestinal X-ray records suggestive of CD were also reviewed. All possible new cases of IBD were then scrutinized by examination of the clinical records, using accepted criteria for confirmation or exclusion of IBD. RESULTS: A total of 215 cases of UC and 72 cases of CD were diagnosed, yielding a mean annual incidence for UC 16.5/100000 (95% confidence interval (CI) 14.4-18.9), and for CD 5.5/100000 (95% CI 4.3-7.0). The highest combined age related incidence for UC was 28.7/100000 in the group aged 30-39 years, and for CD 8.5/100000 in the groups aged 10-19 and 20-29 years. The most common extent in UC was proctosigmoid and the most frequent localization in CD was colonic only. CONCLUSIONS: This prospective study demonstrates a continuing and statistically significant increase in the incidence of both UC and CD in Iceland. The general changes identified for a few previously suggested environmental factors do not allow any firm conclusions as to their role in the observed increase in incidence. It is possible that there are some other causative factor(s).     

The epidemiology of inflammatory bowel disease: a large, population-based study in Sweden

Previous population-based incidence studies of inflammatory bowel disease are limited by small numbers, short duration, or inadequate case-finding. To address these problems, we identified all persons with confirmed ulcerative colitis (n = 2509) or Crohn's disease (n = 1469) in the Uppsala Health Care Region from 1965 to 1983. Age-specific incidence rates by sex were slightly greater for males with ulcerative colitis and females with Crohn's disease. Incidence rates for ulcerative colitis and Crohn's disease were higher in urban than rural areas. The annual incidence rate of ulcerative colitis increased from less than 7 per 100,000 to more than 12 per 100,000 during the study period, while the rate for Crohn's disease remained between 5 and 7 per 100,000. The increase in the incidence of ulcerative colitis was the result of a marked increase in the number of patients with ulcerative proctitis. Analyses by 5-year birth cohorts suggest that those born from 1945 through 1954 were at higher risk for ulcerative colitis and Crohn's disease, and that this effect was accounted for by those born in the first half of the year. The seasonality in the cohort effect, combined with the urban preponderance of disease, suggests that environmental causes may be involved in ulcerative colitis and Crohn's disease.