One in four teen boys in Memphis is having sexual intercourse before the age of 13, according to a new study published Monday.

The study, published in the Journal of the American Medical Association, shows Memphis boys, especially black teens, are having sex before the age of 13 at a rate higher than 16 other metropolitan areas included in the study.

The national average was 7.6 percent, but the study notes the numbers vary greatly by metropolitan area. Memphis's rate was 25 percent for all races of boys.

The study, titled "Prevalence of Sexual Initiation Before Age 13 Years Among Male Adolescents and Young Adults in the United States," pooled previously gathered data from the years 2011, 2014 and 2015 that asked boys and men ages 15 to 24 when they had their first experience with sexual intercourse.

Memphis, which included results from 1,089 men and boys, had the highest rate of cities included in the study. San Francisco had the lowest rate, with 5 percent of boys reporting early sexual activity.

In Memphis, the numbers also vary widely by race. Of black teens, 28 percent reported having their first sexual intercourse before the age of 13, with just 3 percent of white teens reporting the same.

"Health education and counseling can create opportunities for young males, their families, and communities to discuss healthy sexuality, including topics of consent, coercion, and development of sexual expression," the JAMA report read.

Shelby County Health Department Director Alisa Haushalter said the data shows a need to "beef up" youth outreach across the county.

"I think these findings really point out what we're doing, not just in the health department but county-wide, are not sufficient," Haushalter said.

The health department has mainly focused on lowering the county's teen pregnancy and infant mortality rates, and has seen success in both areas.

In 2016, there were 1,110 babies born in the county to moms aged 10-19, according to the Tennessee Department of Health. That was a reduction of 53 percent from the 2,352 kids born to local teens in 2007.

But Haushalter said teens need to learn more about sexuality in general. Too often, she said, they are learning from their peers.

"They actually want information from their parents and other adults in their life," Haushalter said. "So this is a big message I think to those of us who are adults to engage in conversations with youth."

Reach Jennifer Pignolet at jennifer.pignolet@commercialappeal.com or on Twitter @JenPignolet.