AIM: To study the incidence of ulcerative colitis UC in the prefecture of Trikala, Central Greece.

METHODS: A prospective and population based epidemiological study of UC from 1990 to the end of 1994 was conducted. Trikala is a semirural prefecture of Central Greece with a population of 138946 (census 1991). Three gastroenterologists (one hospital based, two private doctors) of the prefecture participated in this study.

RESULTS: During the study period, 66 new histologically verified cases of UC were recorded. The mean annual incidence of the disease in 1990-1994 was 11.2 per 10⁵ inhabitants (95%CI: 8.7-14.3). There was no difference between men and women (annual incidence: 10.5 and 12.0 per 10⁵ inhabitants respectively), either among urban, semirural or rural populations (annual incidence: 11.7, 17.1 and 9.9 per 10⁵ inhabitants respectively). The majority (56%) of the patients never smoked and a quarter were ex-smokers. About a half of all cases had proctitis.

CONCLUSION: UC is common in Central Greece and its incidence is similar to that in North-Western European countries.

Ulcerative colitis (UC) is a chronic inflammatory disease of unknown etiology. During recent years, many epidemiological studies have shown that the incidence of UC varies within different geographic areas. Northern developed countries in Europe, especially United Kingdom and Scandinavia, have a higher rate than in southern countries[1-3]. This geographic variation suggests the hypothesis that some environmental factor(s) and life style may be responsible for the etiology of the disease[3]. Two epidemiological studies showed a different incidence of UC in Greece[4,5].

The aim of our study was to obtain an estimation of the incidence of the disease in Central Greece and to compare our data with those of other parts of Greece and other European countries. The present prospective epidemiological study concerned the prefecture of Trikala, a semirural area of Central Greece.

During the five-year period (1 January 1990-31 December 1994), 66 new cases of definite UC were seen in the area of Trikala (31 males, 35 females). Table 3 shows the incidence of UC by the year of diagnosis and sex. The mean annual incidence of UC over the five years was 11.2/10⁵ inhabitants per year (95%CI: 8.7-14.3). The annual incidence of 5.1/10⁵ in 1990 increased to 17.9/10⁵ in 1994. There were fluctuations in the incidence rates with the highest of 18.7/105 in males in 1994 and the lowest of 5.1/105 in men and women in 1990.

The male/female ratio was 1:0.9. The 95%CI in Table 3 showed the difference in incidence rates between males and females. Table 4 shows the age distribution at the time of diagnosis for all the patients as well as age specific incidence rates. The highest age specific incidence rate was 22.7/10⁵ inhabitants for patients between 30-39 years of age.

Looking at the incidence of UC by sex and place of residence (Table 5), the urban population had an incidence of 11.7/10⁵, the semi-rural 17.1/10⁵ and the rural 9.9/10⁵. The average annual incidence of females living in rural area was the lowest (8.8/10⁵) among women, whereas males living in urban area had the lowest average annual incidence among men (6.9/10⁵).

In relation to smoking, 13 of the 66 patients (19.7%) smoked, 16 (24.3%) were ex-smokers and 37 (56%) non-smokers.

As far as family history of IBD was concerned, in 3 of the 66 patients (4.5%) either UC or Crohn’s disease was present in a first degree relative.

In relation to clinical features, 5 patients (7.5%) had pancolitis, 29 (44%) proctosigmoiditis and 32 (48.5%) proctitis. During the follow up period, in 36 of the patients (54.5%) at least one relapse per year was observed. Hospitalization was required by 8 patients (12.1%) at different times after the day of diagnosis.

Epidemiological studies have found that the incidence of UC varies within geographic areas and within populations of different race.

According to our findings, a UC incidence of 11.2/10⁵ (95%CI: 8.7-14.3) was higher than that reported from other southern European countries[8,9] and within the range of findings in northern Europe[10-12]. In Greece, a retrospective study from north-west Greece [4] showed an incidence of 4.0/10⁵ (95%CI: 3.0-5.0) and a prospective study from Crete[5] showed an incidence of 8.9/10⁵ (95%CI: 7.2-10.4).

The incidence of UC in Trikala prefecture showed an increase during the five years of the study, from 5.1/10⁵ in 1990 to 17.9/10⁵ in 1994. This increase may be attributed to informing programs about the disease, raising the likelihood of people being referred to specialists. Moreover, the application of modern investigative techniques in diagnostic evaluation is likely to explain the increase, although a true raise of the incidence can not be excluded.

The incidence regarding sex was slightly higher for females (12.0/10⁵) compared to males (10.5/10⁵). This finding was remarkable especially in the incidence of 1993, without a special reason to explain it. Another two Greek studies[4,5] did not show this difference. The age-specific incidences, either in males or in females, showed a peak in the age group of 30-39 years. This peak incidence has also been observed by others [4,5,13].

The incidence between urban and rural population was similar, whereas the incidence in semi-rural populations was slightly increased. The average incidence among women living in rural areas (8.8/10⁵) was lower than that among women living in urban areas (16.4/10⁵) and also lower than that among men living in rural areas (11.0/10⁵). This finding has been reported in the study of Crete[5], but it is unclear if it shows true incidence differences or reflects difficulties in access to hospital care and the social shyness of women living in Greek villages.

Regarding smoking, our findings are similar to those reported by others[14,15]. UC was more common between non-smokers and ex-smokers compared with smokers.

According to the anatomical distribution of UC, pancolitis showed a slightly lower proportion compared with other studies[4,5,10,16], but the proportion for proctitis was similar.

Although epidemiological studies presented special problems, we believe that our results represent the true incidence of UC in the prefecture of Trikala. The population of Trikala is relatively stable and with only three specialists and one hospital, it was easy to carry out the study.

In conclusion, the incidence of UC in Central Greece is comparable to that reported from other European countries. The increasing incidence of UC during the five years of the study may be explained by the tendency in Greece to adopt a life-style similar to other European countries. This increase may suggest that environmental determinants, diets and life-styles are probably related to UC.