Research of the impact that size at birth and timing of birth might play on health in later life has been published recently.

Three studies all using UK Biobank data have attracted publicity in the national press, and underline the wide range of studies now being conducted using the resource.

Women who were born in summer more likely to be healthier

Most recent to publish, in the health journal Heliyon, was work led by Dr John Perry at the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge.

Dr Perry and his team found that women who were born in the summer are more likely to be healthy adults. The authors of the study believe that more sunlight – and therefore higher vitamin D exposure – in the second trimester of pregnancy could explain the effect, but more research is needed.

According to the study, birth month affects birth weight and when the girl starts puberty, both of which have an impact on overall health in women as adults.

The environment in the womb leads to differences in early life – including before birth – that can influence health in later life. This effect, called programming, has consequences for development throughout childhood and into adulthood.

The researchers looked at whether birth month had an effect on birth weight, onset of puberty and adult height. They found that children who were born in the summer were slightly heavier at birth, taller as adults and went through puberty slightly later than those born in winter months.

Dr Perry, a Senior Investigator Scientist at the MRC Unit, said:

“When you were conceived and born occurs largely ‘at random’ – it’s not affected by social class, your parents’ ages or their health – so looking for patterns with birth month is a powerful study design to identify influences of the environment before birth.”

The researchers compared the growth and development of around 450,000 men and women from UK Biobank. The results reveal that babies born in June, July and August were heavier at birth and taller as adults. For the first time, the study also revealed that girls born in the summer started puberty later – an indication of better health in adult life.

“We don’t know the mechanisms that cause these season of birth patterns on birth weight, height and puberty timing,” said Dr Perry. “We need to understand these mechanisms before our findings can be translated into health benefits. We think that vitamin D exposure is important and our findings will hopefully encourage other research on the long-term effects of early life vitamin D on puberty timing and health.”

• Read the paper: Season of birth is associated with birth weight, pubertal timing, adult body size and educational attainment.by Day et al. Heliyon, 12 October 2015.

First-born children may develop poorer eyesight

Meanwhile, a large study led by researchers from the School of Optometry and Vision Sciences, at Cardiff University has shown that first-born children are more likely to develop myopia – a term otherwise known as short-sightedness – than later born children.

The study of nearly 90,000 people in UK Biobank showed that first-born individuals were approximately 10% more likely to have myopia, and approximately 20% more likely to have a more severe form of the condition, than later born individuals. The work was published in the journal JAMA Ophthalmology.

Short-sightedness can lead to visual impairment and blindness and is becoming an increasingly important public health issue, partly because it is becoming more common in younger generations in many parts of the world.

The researchers found evidence suggesting that exposure to education may protect later born children from myopia, with parents investing more education activities to first born children, although a causal relationship was not found.

The team, led by Professor Jeremy Guggenheim, write: “The results replicate earlier findings from 2 contemporary international cohorts of adolescents/young adults, implying that the cause of the birth order–myopia association is widespread and has been in existence for several decades. The association was larger before adjusting for educational exposure, suggesting that reduced parental investment in the education of children of later birth order may be partly responsible.”

• The results have been published in the journalJAMA Ophthalmology.

Link between being under-weight at birth with poorer hearing, vision and cognition in middle age

A study by researchers at the University of Manchester, has linked being under and overweight at birth with poorer hearing, vision and cognition in middle age. Very small and very large babies had the poorest hearing and vision concluded researchers in Manchester, Nottingham, Cincinnati and Madison, Wisconsin who analysed the UK Biobank data.

Associations with birth weight – an index of prenatal growth – were complex.  Larger babies falling within the 10th and 90th percentile of weight had better hearing, vision and cognition in adulthood.

But very small and very large babies had the poorest hearing, vision and cognitive function.  Better growth during childhood (as indexed by adult height) was associated with better hearing, vision and cognition in adulthood. The work was published in the journal PLOS One.

Dr Piers Dawes, a lecturer in audiology at The University of Manchester’s School of Psychological Sciences led the study.  He said: “Sensory problems and illness such as dementia are an increasing problem but these findings suggest that issues begin to develop right from early life.

“While interventions in adulthood may only have a small effect, concentrating on making small improvements to birth size and child development could have a much greater impact on numbers of people with hearing, vision and cognitive impairment.”

The researchers used statistical techniques to correct for other sources of impairment such as smoking, economic deprivation and other existing health decisions.

As a result they suggest in the research paper that under-nutrition may impact on development of the brain and sensory systems. Alternatively, growth hormones and changes in genetic regulation may be affected by experiences early in life and impact on neurosensory development.

•  The paper, ‘The Effect of Prenatal and Childhood Development on Hearing, Vision and Cognition in Adulthood’ was published in the journal PLOS One.  The study was facilitated by the Manchester Biomedical Research Centre.