4. Patients' characteristics

Age distribution of the total number of cases could be described according to recommended age groups in 32 countries reporting a total of 107 096 cases. Among these cases, 4% were reported in children (1% in children under five, 3% in the 5 to 14 age group), 77% in adolescents and adults less than 65 years old (11% in the 15 to 24 years age group, 18% in the 25 to 34 group, 20% in the 35 to 44 group, 15% in the 45 to 54 group, 13% in the 55 to 64 group) and 19% in patients aged 65 or more.

Overall, 1.8 times more male than female tuberculosis patients were reported in the 32 countries mentioned above. By country, the sex ratio ranged from 1.0 to 2.6 (median 1.5). It was 1.0 in three countries : Sweden, Iceland (12 cases) and San Marino (2 cases). Seven countries reported more than twice as many cases in males as in females: Armenia, Azerbaijan, the three Baltic states (Estonia, Latvia, Lithuania), Moldova and Romania. The sex ratio was close to 1 among patients aged less than 25 years as well as in patients aged 64 years and over. However, the number of males exceeded that of females in patients between 25 and 64 years of age, with a maximum male to female ratio of 2.9 in the group aged 45 to 54 ( Figure 1).

The age distribution varied across countries. The 18 countries in Group 1 (with incidence rate lower than 20 per 100000) reported a higher proportion of cases in children than the 14 countries in Group 2 : 2% versus 1% in the group 0 to 4, 3% versus 2% in the 5 to 14 years. In adults and adolescents however, the age distribution of cases was shifted towards older age groups in Group 1 compared to Group 2 countries : 27% of the cases in Group 1 were reported in patients aged 65 years or more as compared to 14% in Group 2, while proportionally less cases were reported in the 15-24 age group in Group 1 than in Group 2 (4% versus 13%). This shift towards older age groups in Group 1 countries was even more marked after exclusion of cases reported in patients of foreign origin (data not shown). It is known that countries with low incidence of tuberculosis report proportionally more cases in older age groups mainly due to reactivation of ancient M. tuberculosis infection. However, the lower proportion of children in countries notifying more than 20 cases per 100 000 annually is not consistent and may be due to underreporting. Age and sex distribution of cases in individual countries is illustrated for 29 countries reporting at least 30 cases in 1995 (Country Profiles).

In the same 32 countries, age and sex-specific incidence rates (Figure 2) were lowest in the younger age groups, then increased with age. In males, the incidence rate increased steadily up to the 35-44 age group and remained stable above 44 years of age. In females, incidence rate peaked first in the 25-34 group and again in the older age group (64 years and over). Below 25 years of age, incidence rates were similar in males and in females. Above 24 years, the incidence rate in males was higher than in females (twice as high above 34 years of age). These overall trends resulted from patterns which differed by country, as illustrated by the age and sex-specific incidence rate curves in individual countries (Country Profiles) .

Information on the geographic origin of the patient was available as a binary variable in 21 countries, including 10 defining the origin by the birth place and 11 defining the origin by the citizenship of the patient (Table 2) ). In the 10 countries classifying cases according to birth place, the proportion of cases in foreign-born patients varied dramatically from 1% to 56% (median 40%). Excluding San Marino which reported only 2 cases, four countries (Luxembourg, Denmark, Norway and Sweden) reported more than 40% of their cases in foreign-born patients. In the 11 countries classifying cases according to citizenship, the proportion of cases in foreigners ranged from 1% to 62% (median 24%). Five countries (Belgium, France, Germany, Switzerland and the Netherlands) reported 25% or more of the cases in foreign citizens. Differences in proportion of patients of foreign origin should be interpreted with caution, considering between country differences in the definition of foreign origin as well as in policies regarding acquisition of nationality. In addition, separate population figures for foreign and national populations in each country should be obtained in order to compare incidence rates rather than proportions.

The specific country of birth or of citizenship was available for 14 countries, of which 12 reported at least 5% of cases in patients of foreign origin (Table 4) . Among the seven countries reporting the patient's country of birth, African origin accounted for the highest proportion of foreign-born patients in Denmark and Finland, European origin in Luxembourg and Slovenia, Asian origin in Malta and Norway, and Iceland reported only one case in a foreign-born patient. Among the five countries reporting the patient's country of citizenship, Europe was the most frequent origin of foreign patients reported in Austria and Switzerland, whereas African origin was most frequent in foreign patients from Belgium, Italy and the Netherlands.