Table 1 Characteristics of studies used in the data analysis (N = 45)

Study characteristics

Studies contributing age groups

45

Studies comprising several distinct substudies^a

3

Countries represented

17

Setting

General population

21

Primary care practice

12

Hospital/nursing home

3

Health insurance

8

Several settings (and different data sets)^b

1

Disease classification

Name of diseases/disease groups only

30

Diseases based on international classification systems

15

No. of diseases in the classification

Range of diseases under study

5 to over 300

Median

16

Data collection period

Up to one year

25

One year or more

19

Several periods^c

1

No. of study participants

Range of persons under study

301 to 5.6 million

Median

6864

No. of age groups

1

26

2 to 3

9

4 to 6

10