Table 1 Summary of data collection methods, and demographics of samples, in each country

Random urban (50 %) and rural (50 %) samples aged 18–65 years from general population listings supplied by local municipal authority. Questionnaires distributed and returned by post. No reminders sent.

3000/318

M

136

F

182

Random urban (70 %) and rural (30 %) samples drawn from general population using listings supplied by Azienda Sanitaria Locale of Pavia, stratified with regard to gender, age (in range 18–65 years) and education. Questionnaires distributed and returned by post. No reminders sent.

3500/487

M

203

F

284

Sample drawn from Kaunas city and Kaunas region using Residents’ Register Service, reflecting age (in range 18–65 years) and gender composition of Lithuania and proportions living in rural (33 %) or urban (67 %) areas. Data collection face-to-face, conducted by medical students “cold-calling” door-to-door.

1137/573

M

237

F

336

Sample aged 18–65 years, stratified for age, gender, region and nationality, drawn from general population via national social security registry (IGSS). Questionnaires distributed and returned by post. Reminders sent one month later to non-responders.

6498/1833

M

769

F

1064

Survey conducted by market research company with access to population sample of 200,000, representative with regard to gender, age (in range 18–65 years), region and education. Questionnaire distributed by internet, to be completed on-line. Study stopped when >2000 received back.

unknown/2414

M

1214

F

1200

Random sample of employees of companies operating in national postal services in 10 areas of Spain, stratified to be representative of general working population with regard to gender, age (in range 18–65 years) and education. Ten occupational health physicians delivered and took return of questionnaires. One telephone reminder to non-responders.

1700/999

M

410

F

589

unknown/6624

M

2969

F

3655

All

6624