Sexual behaviour and attitudes of Danish middle-aged men-methodological considerations.

A Danish cohort-investigation of health risk-factors (started in 1976) included descriptions of the sexuality of the participants. This paper examines the validity/representativity of the results of the sexological investigation of the male participants, when in 1987 they were 51 years old. Remaining results will be published in separate articles about each main theme. The participants, 439 men, completed a questionnaire concerning sexuality (behaviour, attitudes and experience) and had their serum-LH and serum-free testosterone measured. Thereafter 100 of the 439 men were interviewed. The present examination shows that the participants are representative of same-aged men from all over Denmark concerning the sexological results. The answer ratio of the questionnaire was 70-95% and the non-responders of the questionnaire gave different interview answers than the rest. Complemented with their answers (answer ratio of nearly 100%) the interview results are more representative than the results of the questionnaire. The interview information is in this study considered more valid than the information obtained by the questionnaire--because the former more frequently than the latter contain answers embarrassing to the participants (e.g. high frequency of masturbation) or difficult for them to recall. The interview thereby adds vital information to that of the questionnaire.