Sexual behaviour related to the spread of sexually transmitted diseases--a population-based survey.

Behavioural patterns pertinent to the spread of sexually transmitted diseases (STD) were assessed in a random sample population study in Sweden. From a sample of 1150 individuals aged 16-31 years, 768 (68%) completed a questionnaire on past and present sexual contacts. Response rate was highest in youngest and oldest age groups. Median age at first intercourse was 16.4 years for women and 17.1 years for men; the woman's partner at first intercourse was a median of 2 years older; men chose partners of the same age for first intercourse. The time to second partner was a median of 2 years; number of lifetime partners increased with one new partner for 2.5 years. Condoms were more frequently used in younger age groups. In all age groups, 5-10% of individuals reported a high-risk behaviour for the spread of STDs.