Harvard researchers analyzed smoking behavior of 90,961 families surveyed between April 2007 and July 2008.

'Overall, we found that the proportion of households that use tobacco products is the same across all age groups, but family members are increasingly more likely to smoke indoors as their children become preteens and teenagers,' said Summer Hawkins, lead study author. 'The reason why secondhand smoke may cause ear infections is not known completely, but secondhand smoke is an irritant and that may increase children’s and adolescents’ susceptibility to ear infections.'

'Parents are usually pretty savvy and know it’s not in their children’s best interest to smoke indoors,' said Ellen Wald, chair of pediatrics for American Family Children’s Hospital in Madison, Wis. 'When they say they never smoke indoors, I’m skeptical. They know that’s the answer people want to hear.'

The study authors suggest that pediatricians should do more to make parents aware of the hazards of secondhand smoke.

'Parents and health care providers need to work together to create a smoke-free environment for their children,' Hawkins said. 'Providers should ask parents about tobacco use during clinic visits. Parents can reduce children’s exposure to secondhand by prohibiting smoke inside the home.'

While no simple answer exists, Wald said, 'In order to change behavior you have to talk about it. Physicians are in a good position to send the message that everyone’s vulnerable to secondhand smoke, not just children and adolescents but adults as well.'