Highlights of the sexual activity of the heterosexual population in the province of Quebec

Objectives: To describe and quantify the level of sexual activity of the he terosexually active population of Quebec. Methods: The data analysed included 2889 heterosexually active individuals aged 15-60 (age(med)=32) from a 1996-7 survey on the sexual lifestyles of t he general population of Quebec. Various probability distributions were stu died to assess their capacity to describe and quantify the lifetime and yea rly numbers of sexual partners of the sampled population. To estimate the a nnual rates of new partner acquisition, a generalised linear model was fitt ed to the number of lifetime sexual partners as a function of age, years of sexual activity, and sex. Results: The mean and variance of the number of lifetime sexual partners fo r men ((x) over bar=11, s(2)=163) is higher than for women ((x) over bar=6, s(2)=72). The negative binomial and lognormal probability distributions gi ve the most adequate fit to the lifetime number of partners for both agglom erated and stratified (by sex and age) data. The estimated annual rates of new partner acquisition provide two important results for prevention: (1) t he first year of sexual activity represents the highest: annual rate of new partner acquisition independent of age, (2) annual rates of new partner ac quisitions increase through mid-life (ages 40-50) combined with a decrease in condom use. Conclusion: Problems caused by the use of large categories in the estimatio n of mean and variance cannot totally be overcome by fitting probability di stributions to the empirical data despite good fits. Furthermore, we believ e that adequate estimates of the annual rate of new partner acquisition sho uld be a better measure of the risk of HIV infection than the number of par tners since the first is a measure of incidence while the second is a measu re of prevalence.