August 22 (HealthDay News) -- Suffering respiratory or ear infections in early childhood, having a dog in the house as a newborn, and even being raised in a large family all appear to increase the risk of snoring later in life, new research suggests.

The findings may seem incidental but, the study authors point out, snoring has been linked with an increased risk of cardiovascular disease, not to mention the obvious problems of sleep deprivation for those who snore and those who have to listen.

"No one has studied this potential cause of snoring," said Karl A. Franklin, lead author of a study in the Aug. 22 issue of Respiratory Research and an associate professor of respiratory medicine at University Hospital in Umea, Sweden. "We found that early life infections, recurrent otitis, having a dog as a newborn, and growing up in a larger family was independent of each other and independent of other confounders related to snoring in adulthood."

Another expert, however, points to the study's weaknesses.

"The study has limitations," said Dr. Raanan Arens, chief of respiratory and sleep medicine at the Children's Hospital at Montefiore in New York City. "This is a very general study based on a questionnaire that simply was distributed to a large number of subjects. You could find statistical significance; however, the meaning of this significance to the clinical arena is unclear."

According to background information in the study, some 16 percent of middle-aged men and 7 percent of women snore habitually.

Often in snorers, the size of the upper airways is reduced. Snoring is also a symptom of obstructive sleep apnea, when people actually stop breathing briefly while asleep. Obesity, age, smoking and chronic bronchitis all increase the risk of snoring.

Early life environment has been shown to impact a multitude of health conditions later in life.

These authors randomly selected almost 16,000 men and women aged 25 to 54 in Denmark, Estonia, Iceland, Norway and Sweden, asking them to fill out a questionnaire soliciting information on how often and how loudly they snored in adulthood and environmental factors in their childhoods.

Eighteen percent of respondents reported "loud and disturbing" snoring at least three nights a week.

People who had been hospitalized for a respiratory infection before the age of 2 were 27 percent more likely to be "habitual snorers." Those who suffered from recurrent otitis or ear infections as a child were 18 percent more likely to snore, growing up in a large family increased the odds slightly, while having a dog at home as a newborn increased the odds by 18 percent.

All of the same factors except household size were also linked with combined snoring and daytime sleepiness.

"We speculate that all these factors could promote an enlargening of tonsils with mouth breathing and a subsequent change of the mandibular growth that could promote snoring in adulthood," Franklin said. "Further studies are needed."

SOURCES: Karl A. Franklin, M.D., Ph.D., associate professor, respiratory medicine, University Hospital, Umea, Sweden; Raanan Arens, M.D., chief, Division of Respiratory and Sleep Medicine, Children's Hospital at Montefiore, New York City; Aug, 22, 2008, Respiratory Research