A young woman’s sex life may influence her risk of kidney infection.

New research shows that women younger than 50 who have sex at least three times per week, take a new partner, or recently used spermicides have a higher risk of kidney infections.

Diabetes, urinary incontinence, and a history of a urinary tract infection are also important, according to a study in the Jan. 4 issue of the Annals of Internal Medicine. The findings could help more women avoid kidney infections.

Kidney infections are common. Every year, they send more than a quarter of a million Americans to doctors’ offices and 200,000 people to hospitals.

Most of those patients are women. It’s rare for women who are otherwise healthy (and not pregnant) to be hospitalized for kidney infections. Instead, they usually get treatment with antibiotics.

Until now, little was known about kidney infections in younger women. Closing that knowledge gap was the goal of Delia Scholes, PhD, and colleagues. Scholes is a senior researcher with the Center for Health Studies at Group Health Cooperative, a Seattle-based health plan.

First, the researchers interviewed 240 young women with kidney infections. Participants were 18-49 years old and members of Group Health Cooperative. Interview topics included sexual behavior, diabetes, urinary tract infections, and urinary incontinence. Next, the researchers reviewed similar data on more than 500 healthy women without a history of kidney infections.

Several kidney infection risk factors stood out:

Frequent sexual intercourse. Frequent sexual intercourse (greater than three times per week) over the last 30 days was found to increase the risk of kidney infections more than fivefold.

Recent urinary tract infection. Women with kidney infections were more than four times as likely to have recently had a urinary tract infection.

Diabetes. Kidney infection was nearly four times more likely to occur in women with a history of diabetes. Overall, only about 3 percent of the group had diabetes.

Recent urinary incontinence. Participants with kidney infections were almost four times as likely to have had trouble holding in their urine in the past month.

New sexual partner. Women who had kidney infections were nearly twice as likely to have had a new sex partner in the previous year.

Recent spermicide use. Women with kidney infections were almost twice as likely to have recently used a spermicide.

Mother with a history of urinary tract infections. Participants with kidney infections were about 1.5 times as likely to have a mother who had urinary tract infections.

It’s likely that infections can travel up to the kidneys from lower parts of the urinary tract, such as the bladder. So preventing infections of the bladder, which have many of the same risk factors, may help avoid kidney infections, say the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Scholes, D. Annals of Internal Medicine, Jan. 4, 2005; vol 142: pp 20-27. News release, Group Health Cooperative and the Center for Health Studies.