ATLANTA (AP) — Health officials say there’s been a dramatic drop in the number of ear infections in young children.

It’s not clear why, but some researchers suggest a decline in smoking by parents might be part of the reason.

Harvard researchers say fewer people smoke, which means less irritation of children’s airways. In children, the ear is more directly connected to the back of the nose, so infections in a child’s nose and throat can easily trigger ear inflammation. Cigarette smoke, inhaled through a child’s nose, can trigger the same kind of irritation and swelling.

Other doctors say the decline in ear infections may be due to the growing use of a vaccine against the bacteria that cause them.

And some think increased breast-feeding is protecting more children. Breast milk is rich in antibodies.

Whatever the reason, figures from the Centers for Disease Control and Prevention show a 30 percent drop in young children’s doctor visits for ear infections over 15 years.

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