Watchful waiting may be a good strategy when the condition is not too severe.

More than 530,000 children have their tonsils or adenoids removed in the United States each year to prevent recurrent infections and sleep or breathing disorders. But a new study suggests that the surgery may have long-term risks that in some cases outweigh any short-time benefits.

The report, in JAMA Otolaryngology — Head and Neck Surgery, compared 60,667 Danish children under 9 who had tonsillectomies, adenoidectomies or both with 1.1 million who had not had the surgeries. They were born between 1979 and 1999, and researchers followed their health for up to 30 years.

After controlling for many health factors, they found that tonsillectomy was associated with almost triple the relative risk of diseases of the upper respiratory tract. Adenoidectomy was associated with about double the relative risk of obstructive pulmonary disorder, upper respiratory tract diseases and conjunctivitis.

The surgery has some short-term benefits in cases of abnormal breathing, sinusitis and ear infections, but the long-term risks for those conditions were either significantly higher after surgery or not significantly different.

“This is the first study to look at long-term risks,” said the lead author, Sean G. Byars, a research fellow at the University of Melbourne. “With some kids, knowing that there are future risks may cause people to hold off, use pain medication and so on. Watchful waiting may be a good strategy when the condition is not too severe.”