Why the eldest child is the unhealthiest of them all

First born children may have a head start in life, but they are heir to a host of other ailments.

They are prey to unhealthy conditions which may curtail their longevity.

From obesity to raised dietary fat and high blood pressure, being the eldest child is not always an advantage, a new study has found.

While firstborn have the bonus of their parents' undivided attention and resources, it can become a burden.

The stress of having to succeed at school, and meet career expectations, may be behind some of their health issues too, it is suggested.

The research - one of the largest of its type - was based on the health records of almost 400,000 Norwegians over nearly a quarter of a century.

Lead author Professor Sandra Black of the University of Texas at Austin said: 'Overall, we find that first-borns are less healthy in terms of physical markers such as blood pressure, triglycerides, and indicators of overweight and obesity.

'For example, compared to fifth-borns, first-borns are about 5 per cent points more likely to be obese and 7 per cent more likely to have high blood pressure. So, unlike education or earnings, there is no clear first-born advantage in health.

'However, first-borns are about 13 per cent less likely to smoke daily than fifth-borns and are more likely to report good physical and mental health. Later-borns also score lower on well-being with fifth-borns being about 9 per cent less likely than first-borns to report that they are happy.

'When we explore possible mechanisms, we find that early maternal investment may play a role in birth order effects on health.'

The study found that the probability of having high blood pressure declined with birth order and the largest gap is between first- and second-borns.

Second-borns are about 3 per cent less likely to have high blood pressure than first-borns; fifth-borns are about 7 per cent less likely to have high blood pressure than first-borns.

The stress of having to succeed at school, and meet career expectations, may be behind some of their health issues too, it is suggested (file photo)

The stress of having to succeed at school, and meet career expectations, may be behind some of their health issues too, it is suggested (file photo)

They also found higher levels of high triglycerides - a form of dietary fat made by the liver - for first-borns than for second- or third-borns.

While first-borns are still taller - by just 1/8th of an inch over each succeeding child - they are also more likely to be overweight and obese. Compared to second-borns, first-borns are 4% more likely to be overweight, and 2per cent more likely to be obese.

This may be down to their being breastfed for an extra two weeks , on average, it was suggested.

Even being breastfed for two extra weeks, on average, has its drawbacks.

However the eldest child is more likely to be happy and consider themselves to be in good health Mental health generally declines with birth order.

The study in the journal Economics and Human Biology, said that the sex of the first born did not play a part: 'While there are some differences by gender, there is no strong systematic pattern and, in general, the coefficient sizes are similar across gender.'

Adding: 'First-borns have higher average education and earnings than later-borns – so this is a plausible explanation for poorer health outcomes of later-borns.

'However, it cannot explain the fact that later-borns have better health along some dimensions such as having lower risk of high blood pressure and obesity.

'First-borns are, on average, lighter at birth than their siblings. Lower nutrient flow to first-borns in utero may affect their regulation of fat and cause them to store more fats in adulthood. This may partly explain the greater propensity of first-borns to be obese.

'The resulting catch-up growth of first-borns also leads to a greater tendency towards high blood pressure. Thus, the greater likelihood of high blood pressure and obesity for first-borns may be largely biologically determined.

'Another potential mechanism is personality. While the empirical evidence is not particularly strong, there is an established set of theories about birth order and personality.

'First-borns are often perceived to be intense and career-orientated while later-borns are considered to be more laid back and creative .

'This provides a possible set of explanations for our findings about blood pressure. High blood pressure and triglycerides may be caused by the stress that results from this driven, competitive personality type.'

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