Survey response rates: national and regional differences in a European multicentre study of vertebral osteoporosis.
O'Neill TW., Marsden D., Matthis C., Raspe H., Silman AJ.
STUDY OBJECTIVE: This analysis aimed to compare the response rates of those invited to attend for screening in a multicentre, multinational study within Europe. DESIGN: This was a population survey. SETTING: Thirty four centres in 16 European countries. SUBJECTS: Men and women aged 50 years and over were recruited from population based sampling frames to participate in a prevalence survey of osteoporosis. Subjects were invited by post to attend for radiological screening and interview, and non-responders were followed up by repeat mailing. RESULTS: There was a substantial variation between centres in response rates: the mean was 49% and the range 5-83%. Adjusting for those known to have died or moved house did not affect the overall ranking. The response rates to each mailing also varied between centres: first mailing 45% (range 5-83%) and second mailing mean 10% (range 0-23%). The response rates varied in relation to age and sex and were higher in women than men. Rates fell gradually with age in women but rose in men until the age of 65 years. Response rates varied regionally. These were highest in countries from northern Europe and lowest in southern European countries, but there was wide variation both within regions and within countries. CONCLUSIONS: Multicentre, multinational studies within Europe will probably become increasingly popular. In this study, despite a standardised approach, the range in response rates between centres both within and between countries was substantial. Attempts at cross national standardisation in survey design can have only a limited effect on yielding uniformity in response.