Season of birth linked to allergy risk

the US, allergies are the sixth leading cause of chronic illness, affecting more than 50 million Americans and costing over $18 billion each year. Though we cannot choose the season in which we are born, researchers have found a link between season of birth and allergy risk in later life, with autumn and winter babies faring worse.
Baby with eczema
Babies born in autumn have an increased eczema risk, researchers say.

The new study is published in the journal Allergy.

Previous research has linked birth month with various health outcomes. A 2015 study, for example, found that 55 diseases correlate with season of birth. Researchers from that study concluded that babies born in October had the worst lifetime risks.

And another study suggested that summer babies grow up to be healthier adults, pointing to maternal vitamin D exposure during pregnancy and its effect on offspring.

However, although there have been many studies into birth month and health risks, until now, little has been known about how a so-called one-time exposure – such as season of birth – has lasting effects.

To investigate further, researchers from the University of Southampton in the UK conducted epigenetic scanning on DNA samples from people born on the Isle of Wight off the southern coast of the UK.

The term epigenetics refers to any process that changes gene activity without changing the DNA sequence itself. These changes lead to modifications that can be transmitted to other cells.

Although epigenetic processes are a natural part of our body’s functions, there can be negative health effects if they happen improperly.

Autumn and eczema

The most-studied epigenetic process is DNA methylation, which is the addition or removal of a methyl group. It was first identified in human cancer in 1983, and it has since been linked to many other health conditions.

“Epigenetic marks are attached onto DNA,” explains Prof. John Holloway, study author from the university, “and can influence gene expression (the process by which specific genes are activated to produce a required protein) for years, maybe even into the next generation.”

After measuring whole blood epigenome-wide DNA in 367 participants, the researchers found that DNA methylation was associated with birth season, and it was still present 18 years later.

Additionally, the researchers were able to link the birth season epigenetic marks to allergic diseases. In detail, people born in autumn had an increased eczema risk, compared with those born in spring.

Their results were also validated in a cohort of Dutch children.

“These are really interesting results,” says Prof. Holloway. “We know that season of birth has an effect on people throughout their lives. For example generally, people born in autumn and winter are at increased risk for allergic diseases such asasthma. However, until now, we did not know how the effects can be so long lasting.”

‘Health horoscope’

Prof. Holloway adds that their study has linked DNA methylation with season of birth and risk of allergy, but he cautions that, while the findings have clinical implications, they “are not advising altering pregnancy timing.”


Summer babies grow up to be healthier adults

Researchers from the study, published in the journal Heliyon, come from the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge in the UK.

They say their findings support the “fetal programming” hypothesis, which suggests that the environment in the womb leads to early life differences that can then affect health later in life.

Previous studies have found that birth season – which is indicative of in-utero vitamin D exposure – is associated with a wide range of health effects. The researchers note that “the most compelling associations to date appear to be those with immune-related disease, such as type 1 diabetes and multiple sclerosis.”

Meanwhile, other studies have suggested a link between season of birth and birth weight.

“When you were conceived and born occurs largely at random,” says lead author Dr. John Perry, “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.”

He and his team believed the time during childhood growth and development is a significant link between early life and later health, so they set out to study the impact of birth month in more detail – investigating whether birth month had an effect on birth weight, onset of puberty in girls and adult height.

Babies born June-August have higher birth weights, are taller adults

To conduct their research, the team used data from the UK Biobank study – a major national health resource – to compare the growth and development of about 450,000 men and women. According to the team, this is the “most comprehensive assessment to date of the impact of birth season on childhood growth and physical development.”

Results showed that babies who were born in June, July and August had higher birth weights and were taller as adults, and girls born during these months started puberty later – which is an indicator of better health in adulthood.


Zika: risk of microcephaly 1 in 100 with infection in early pregnancy

Around 1 in 100 women infected with Zika virus in the first trimester of pregnancy are at risk of microcephaly, according to estimates of a new study published in The Lancet.

Study coauthor Dr. Simon Cauchemez, of the Institut Pasteur in Paris, France, and colleagues say their findings provide further evidence that Zika virus is associated with increased risk ofmicrocephaly – a neurological condition that can result in babies being born with smaller-than-normal heads.

Last month, the World Health Organization (WHO) declared Zika virus as a public health emergency of international concern, a decision spurred by the suspected link between Zika virus and microcephaly.

While the association is yet to be scientifically proven, there has been a surge in microcephaly cases in Brazil, where Zika virus transmission is ongoing; microcephaly incidence in the country is around 20 times higher than that of previous years.

‘Strong statistical support’ for link between Zika and microcephaly

For their study, Dr. Cauchemez and colleagues used serological and surveillance data to assess incidence of microcephaly during the Zika outbreak in French Polynesia, which took place between October 2013-April 2014.

Fast facts about microcephaly

  • Microcephaly occurs when the baby’s brain does not develop properly during pregnancy or stops growing after birth
  • In the US, microcephaly is estimated to affect between 2-12 babies per 10,000 live births
  • The causes of microcephaly are unknown for most babies.

Learn more about microcephaly

During this period, 66% of the general population were infected with Zika virus, and eight cases of microcephaly were identified; seven of these occurred within a 4-month period near the end of the Zika outbreak.

Using mathematical and statistical modeling, the researchers estimated the risk of microcephaly with Zika virus infection during six different periods of pregnancy – trimesters one and two; trimesters one, two and three; trimester two; trimesters two and three; and trimester three – and compared their estimates with actual number and timing of Zika virus and microcephaly cases.

To reach their estimates, the team used data on the total number of microcephaly cases, the weekly number of consultations for suspected Zika infection, the total number of births that occurred during the outbreak, and blood tests taken prior to the outbreak that confirmed the presence of Zika virus antibodies.

The researchers found that women who were infected with Zika virus in the first trimester of pregnancy were at greatest risk for microcephaly, with this situation most closely matching the actual data.

The team calculated that 95 in 10,000 – or around 1 in 100 – women infected with Zika virus in the first trimester of pregnancy are at risk of microcephaly.