Abstract
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OBJECTIVE: Our objective was to determine how the risk of acquisition of herpes simplex type 2 infection varies with age and sex in early adulthood.
DESIGN/ SETTING: A cohort study of 1037 children established at age three from those born in Dunedin, New Zealand in 1972/3.
PARTICIPANTS: At the age 32 assessment, 884 participants (432 women and 452 men), 87.1% of the surviving cohort, provided both sera and information on sexual behaviour.
MAIN OUTCOME MEASURES: We measured the proportion with antibodies to HSV-2 infection at ages 26 and 32, then calculated the incidence rates from first coitus to age 26 and from age 26 to 32, adjusting for the number of sexual partners and same sex contact in these age periods.
RESULTS: At age 32, 14.6% of men and 22.5% of women had antibodies to HSV-2. Up to age 26 the incidence rates were 6.5 and 14.3 per 1000 person-years for men and women respectively. From age 26 to 32 the incidence rates were 14.3 and 15.8 per 1000 person-years for men and women respectively. When adjusted for sexual behaviour, the incidence rate ratio, comparing the older to the younger age periods, was 2.9 (95% confidence interval 1.7 to 4.9) for men and 2.0 (95% confidence interval 1.2 to 3.4) for women. Comparing women to men, up to age 26 the adjusted incidence rate ratio was 2.5 (95% confidence interval 1.6 to 4.0) and from age 26 to 32, 1.3 (95% confidence interval 0.78 to 2.2). A test for interaction indicated that men and women had different patterns of incidence over time (p=0.039).
CONCLUSION: In the general population, risk of acquiring HSV-2 infection appears to increase with age at least to the early 30s, and differences in risk of acquisition for women compared to men become less with age. Health promotion and treatment to control HSV-2 infection should be aimed at all ages, not just the young.