LAUSR

Sexual behavior information can provide context for understanding rates of sexually transmitted infections (STI) and inform potential impact of interventions. We used 2013–2016 National Health and Nutrition Examination Survey (n = 4930) and 2011–2015 National Survey of Family Growth (n = 16,643) data from sexually experienced 20–44-year old US females and males to estimate the number of lifetime and past year partners and percent with a new past year partner overall and by marital status, in 5-year age groups. Group differences were qualitatively assessed. Estimates from both surveys were comparable. The median number of lifetime sex partners ranged from 4.2 to 5.2 across age groups among females and was higher among older (9.1) than younger (4.6) males, persons with a new past year partner than those without, and persons widowed/divorced/separated/never married than those married/living with partner. Percents with ≥ 2 past year partners and a new past year partner were highest in the youngest age group and lower with age. Percent with a new past year partner was 19–46 percentage points higher in persons widowed/divorced/separated/never married (range 21.7–56.4%) compared to persons married/living with partner (range 2.7–12.4%). In the USA, there are differences in sexual behaviors by gender, age, and marital status. The percent of adults with a new sex partner is lower with increasing age; however, a portion of all subgroups reported having had a new sex partner in the past year indicating some adults remain at risk of acquiring an STI. These data can help inform policies for STI screening and other interventions.