Potty training before age two linked to increased risk of later wetting problems

"Parents who train their children early to meet preschool deadlines, to save landfills from diapers or because they think toddlers are easier to train should know there can be serious repercussions," says lead author Steve Hodges, M.D., an associate professor of pediatric urology at Wake Forest Baptist.

The study, reported online in Research and Reports in Urology, involved 112 children ages 3 to 10. About half were seen in the urology department for daytime wetting or urinary urgency/frequency. They were compared to a group seen in a general pediatric clinic and pediatric emergency room who had no history of dysfunctional voiding.

A questionnaire was used to gather information on the age toilet training was initiated and the presence of daytime voiding dysfunction. Patients were grouped into three categories of potty training: early (before age 2), normal (between 2 and 3) and late (after age 3) training. There were 38 early, 64 normal and 10 late trainers.

Sixty percent of the early trainers had daytime wetting. They had a 3.37 times increased risk of daytime wetness as compared to the normal group. The researchers believe early trainers are more prone to subsequent voiding dysfunction because they are more apt to "hold" their stool or urine. "When children hold stool, it backs up in the rectum," Hodges explained. "The enlarged rectum presses against the bladder, reducing its capacity and causing the nerves feeding the bladder to go haywire."

In fact, in the current study, early trainers were three times more likely to complain of constipation than normal trainers. "Almost all of the children who had wetting also had constipation," Hodges noted.

Younger children also are more apt to delay peeing, behavior that can lead to bladder contractions and reduced bladder capacity. "Research has demonstrated that bladder growth continues in children up to the point of toilet training," said Hodges. "Uninhibited voiding in diapers is likely beneficial to bladder development. In my practice, it's often the children who trained earliest and most easily who end up with the most severe voiding problems."

The study also found that among the 10 children who trained after age 3, seven had daytime wetting problems, and these same seven also were constipated. The three late trainers who did not have wetting problems were not constipated.

"This does not mean late potty training causes dysfunctional voiding," Hodges explained. "It means that when kids train late, it's very likely because they are already constipated, which makes toilet training extremely difficult. Parents whose 3- or 4-year-olds have trouble training are often blamed for 'waiting too long,' but our data suggest waiting isn't the problem -- instead it's likely constipation."

Hodges said constipation in children often goes undiagnosed because pediatricians, following International Children's Continence Society guidelines, simply ask parents whether their children's bowel movements are infrequent and if stool consistency is hard.

"These questions fail to detect enlarged rectums that compromise bladder capacity," said Hodges. "Children can have daily bowel movements and still be constipated. Extra-large stools and stools shaped like pellets or logs are far more indicative of constipation than bowel-movement frequency. But an X-ray will provide a definitive diagnosis."

Hodges advises parents to initiate toilet training when children show signs of readiness -- and have absolutely no signs of constipation -- rather than at a certain age.

"There is nothing magic about the age of two," said Hodges. "If parents opt to train early or late and are meticulous about making sure children void on a regular schedule and monitor them for signs of constipation, I suspect the incidence of voiding dysfunction would decrease."

Hodges said his study is the first to consider constipation status along with age of potty training. Other studies have found late trainers are more prone to dysfunctional voiding and concluded there's a "magic window" before age 3 during which children can avoid problems. "But these studies never considered whether the late trainers were constipated when parents tried to train them," Hodges said.

Hodges has written a book for consumers that covers this and other toileting issues in children.