A new study shows that infants who weigh less than five and a half pounds at birth often enter the world with a host of medical complications, including respiratory problems.
The study has also shown that these respiratory problems may persist well beyond their infancy and childhood and into adulthood.
"We report a previously unrecognized excess risk of hospitalization for respiratory illnesses in young adults with a history of low birth weight," wrote lead researcher Eric C. Walter, M.D., of the University of Washington Division of Pulmonary and Critical Care.
The researchers used hospitalization records from the Washington State Comprehensive Hospital Abstract Reporting System's discharge database between January 1, 1998 and December 31, 2007.
They selected as potential cases any person who was 18 years old at the time of hospitalization and who was discharged with a respiratory code listed among the top four diagnoses.
They then linked these cases to birth weight data listed on birth certificates where possible. Control subjects were randomly selected from birth certificate data.
They found that individuals with very low birth weight (less than 1.5 kg, or 3.3 lbs.) or moderately low birth weight (1.5 to 2.5 kg or 3.3 to 5.5 pounds) had a 83 and 34 percent higher risk of hospitalization for respiratory diagnoses respectively.
Those who had a history of very low birth weight had twice the risk of being hospitalized for asthma or respiratory infection and 2.6 times the risk of respiratory failure requiring mechanical ventilation.
After adjusting for covariates, including demographic characteristics and maternal smoking, the significant association between birth weight and risk of hospitalization persisted.
Furthermore, while the data could not definitively prove a linear link, researchers did note a trend toward greater risk of respiratory problems with lower birth weights.
"In our study the percentage of respiratory disease attributable to moderately or very low birth weight was estimated to be 1.8 percent. If this were extrapolated to the 1.2 million U.S. hospitalizations for respiratory illnesses per year for ages 18 to 44, low birth weight may account for over 22,000 adult hospitalizations per year, with charges in excess of 225 million dollars per year," said Dr. Walter.
The study appears in the July 15 issue of the American Journal of Respiratory and Critical Care Medicine.