Thanks to advances in neonatal medicine, premature babies have been surviving at lower and lower birthweights. There has always been a question mark over how well these infants will develop and what health problems they might face in adulthood, and the New Zealand Very Low Birthweight Study has been tracking one group born in 1986 weighing less than 1500g.
So far, the news is good for most, says paediatrician and neonatalist Brian Darlow, who has led this longitudinal study at the University of Otago from the outset. Although about 5% were dealing with severe disability and another 5% had moderate disability, most were leading healthy and productive lives, despite their difficult start.
“They do have some problems, but all of us have problems and challenges, and the overall message is that the vast majority of this group are doing absolutely fine,” says Darlow.
Each year, about 4500 babies are born pre-term (before 37 weeks of gestation). That puts them at greater risk of heart and lung problems, hearing and sight issues and developmental delays.
When the 1986 very low birthweight cohort reached the age of 28, Darlow and his team brought 229 of them to Christchurch for a comprehensive assessment covering physical and mental health. They were compared with a control group of 100 people who had been born full-term.
On average, the very low birthweight participants had slightly higher blood pressure – although it was still in the normal range – and smaller hearts. One third had evidence of some impairment of lung function and there were subtle differences in brain structure. Using 10 biomarkers associated with ageing, including blood lipid levels, kidney function, periodontal disease and blood sugar, the researchers showed they were ageing faster than their full-birthweight peers.
“Everything we measured was in the normal range, but slightly on the wrong side of the ledger compared with the control group,” says Darlow. “What we don’t know is whether things like blood pressure will continue to progress upwards at a faster rate and if that will mean they have health problems sooner.”
All of us can slow the biological clock to some extent by making healthy choices – eating well, exercising, not smoking, etc.
“It’s probably more important for this group than the average person, and one of the things I hope the research will help do is get that message across,” says Darlow.
The other message he is keen to communicate is that being born very prematurely is a lifetime condition and people need to take extra care to monitor their health – particularly blood pressure, heart, lung and kidney function and blood sugar – so medical intervention can be taken early to prevent longer-term damage.
“There is no set of recommendations at the moment in New Zealand,” says Darlow. “Generally, a GP wouldn’t ask what gestation you were born at or what your birthweight was. And they ought to, particularly if they’re looking at things like blood pressure and lung disease. Patients should offer that information to their doctor if they’re not asked it.”
Darlow would also like to see health checks in childhood and adolescence for low-birthweight people, so that lung and kidney function, blood pressure and blood sugar control can be assessed early on and perhaps rechecked every decade through adulthood.
Data from the New Zealand Very Low Birthweight Study is being pooled with international research to get a bigger picture, but broadly speaking, all are showing a similar encouraging result. Darlow hopes the 1986 cohort will continue to be followed through their 40s and 50s, as that is when health problems such as heart failure and chronic lung disease are more likely to show up if the group continues having accelerated ageing.
While he has now retired, a colleague, Sarah Harris, is taking over the study and will be seeking funding to bring the group back to Christchurch for more assessment in their 40s.
Darlow says, “This is a unique opportunity to increase our understanding of the long-term impact of premature birth on health and wellbeing.”
