The study, which is shortly to be published in the American Journal of Respiratory and Critical Care Medicine, reports on 142 children living in Australia who had taken part in an international clinical trial to investigate the short- and long-term effects of caffeine therapy on preterm babies.
Five out of every 1,000 babies are born very prematurely and weigh only between 500 and 1,250 grams (1.1 and 2.8 pounds) at birth. Between 30 and 40 percent of these preemies either die or continue to live with lasting disabilities.
Caffeine is one of the most widely used drugs in the neonatal intensive care unit (NICU). It is used to treat or prevent respiratory and lung problems in premature babies and to reduce the length of time that they need assistance with their breathing.
“Previous studies have shown that caffeine, which belongs to a group of drugs known as methylxanthines, reduces apnea of prematurity, a condition in which the baby stops breathing for many seconds,” says lead author Lex W. Doyle, professor of neonatal pediatrics at the Royal Women’s Hospital in Melbourne, Australia.
He explains that NICU use of caffeine also reduces the risk of injury and abnormal development in premature babies’ lungs. This condition, called bronchopulmonary dysplasia, can result in breathing difficulties later in life.
Trial on effects of preemie caffeine therapy
The new study follows up children who took part in an Australian site of the international Caffeine for Apnea of Prematurity (CAP) randomized controlled trial.
As part of the follow-up for the trial, when they reached the age of 11, the 142 children underwent lung function tests called “expiratory flow rates” that assess the ability to breathe out air.
When they had been in the NICU as premature babies, 74 (52 percent) of the children had been treated with caffeine, and 68 (48 percent) been given a placebo.
The team found that the children in the caffeine group had significantly better expiratory flow rates than the children in the placebo group.
In terms of statistical significance, the caffeine group’s expiration flow rates were better than the placebo group’s by around one half of a standard deviation. This was true of:
- FEV, the forced expiratory volume in one second, which measures the amount of air a person can exhale with force during 1 second.
- FVC, the forced vital capacity, or the amount of air that a person can forcibly exhale after taking the deepest breath they can.
- FEF25-75%, the average rate of flow from the point at which 25 percent of air has been exhaled to the point at which 75 percent has been exhaled during FVC.
The analysis also showed that the ratio of FEV1 to FVC (FEV1/FVC), which is used as a measure of obstructive lung disease, was also better in the caffeine group than the placebo group. The improvement was smaller than for the other measures but still statistically significant.
Benefit likely result of reduced lung injury
The researchers note that a drawback of their analysis is that the tests only measured expiratory flow rates and that the children came from only one of the many sites involved in the CAP trial.
Prof. Doyle, who is also head of the Australian National Health and Medical Research Council’s Centre of Research Excellence in Newborn Medicine, says, “It would be desirable to repeat lung function more extensively later in life, and at more sites to identify those participants at highest risk of developing severe breathing disorders in adulthood.”
He also notes that if there was only one opportunity to repeat the lung function test, then it should be when the children are around 25 years old, the age at which lung function peaks.
He and his colleagues do not believe that the improvement in breathing in childhood comes from any direct effects of the caffeine molecule on the lungs.