WEDNESDAY, Sept. 7 (HealthDay News) -- Parents who smoke at home could jeopardize their children's academic success and harm their family's finances in ways that go beyond that of spending lots of money on cigarettes, according to a new study.

The research, done at Massachusetts General Hospital, found that children living with smokers have higher rates of respiratory illness and missed one to two more days of school per year than their classmates, possibly causing academic troubles.

Moreover, the study found that the family's finances were undermined when caregivers had to miss work and stay home to care for their children when they got sick.

Nationally, family members who stayed home to care for children with smoking-related illnesses lost at least $227 million annually in forfeited wages and productivity, the study reported. The true figure probably was higher because missed workdays during school vacations were not included, the researchers added.

Noting that the damage of second-hand smoke on youngsters' health has been known for some time, one of the study's authors said the new research found even more harm resulting from smoking at home.

"The main point is that the harm of cigarette use is more than just health harm. It affects kids' access to education and households' bottom lines," said lead study author Douglas Levy, an assistant professor of medicine at Harvard Medical School in Boston.

Over time, parental smoking at home may result in lower achievement at school for their children, the study suggested, pointing to other research that connected missed schooldays and lower academic performance.

In addition, because smokers "have lower incomes, on average . . . the economic impact can be potentially serious" for the families affected, said Levy, who is also an assistant in Health Care Policy at the Mongan Institute for Health Policy at Mass General. Some may risk job loss entirely, the study found.

The research findings were released online this week in advance of publication in the October print issue of the journal Pediatrics.

Overall in the United States, roughly one-third of children live in a home with a smoker, according to an earlier study by Dr. Jonathan P. Winickoff, assistant professor of pediatrics at Harvard Medical School and a co-author of the new research.

More than half of all children in the United States aged 3 to 11 have detectable levels of cotinine in their blood, a chemical caused by second-hand smoke, according to the authors.

The study looked at records, culled from the 2005 National Health Interview Survey, of more than 3,000 children aged 6 to 11 years. About 14 percent of the children in the study lived with someone who smoked at home.

The average annual income of families in the study was $20,087. Single parents headed 22 percent of the households with smokers.

The data was adjusted to account for factors that could affect school attendance, including socioeconomic class, family structure, race and gender. But it still showed that children of smokers missed more school time than their peers, and that about one-quarter to one-third of all class time they missed was due to illness connected to second-hand smoke.

The researchers also found that in homes where two parents or caregivers smoked, the children missed even more school time than in homes where only one parent smoked.

Children of smokers were more likely to have had either a chest cold in the two weeks before they were surveyed or more than three ear infections in the prior year, although the investigators found no link to a higher rate of vomiting or diarrhea.

The study found no link between parents' smoking at home and asthma. But only a small portion of children in the study had asthma, making it statistically unlikely that a connection would be found, said Levy. He noted that other research has already established that link.

The study authors said that absenteeism among children aged 6 to 11 could be reduced by 24 to 34 percent by eliminating smoking in the home.

Calling the database used in the research "the gold standard survey, huge and detailed," an expert in California said the study was "quite well done."

"They applied standard statistical methods to answer the questions they were asking," said Dr. Stanley Glantz, a professor of medicine at the University of California at San Francisco and director of the school's Center for Tobacco Control Research and Education.

Exposure to second-hand smoke has decreased over the last 20 years due to family rules about smoking in homes, and laws banning it in public places, according to the U.S. Centers for Disease Control and Prevention in Atlanta.

Glantz said parents are beginning to be more aware of the effect of second-hand smoke on children. "There has been a lot of movement on this issue in the last few years," he said.

More information

To learn more about second-hand smoke, visit the U.S. Centers for Disease Control and Prevention.