We hear a lot about women’s biological clock and how age affects the chance of pregnancy.

New research shows men’s fertility is also affected by age. When dads are over 50, the risk of pregnancy complications increases.

Data from more than 46 million births in the United States between 2011 and 2022 compared fathers in their 30s with fathers in their 50s.

While taking into account the age of the mother and other factors known to affect pregnancy outcomes, the researchers found every ten-year increase in paternal age was linked to more complications.

The researchers found that compared to couples where the father was aged 30–39, for couples where the dad was in his 50s, there was a:

• 16% increased risk of preterm birth
• 14% increased risk of low birth weight
• 13% increase in gestational diabetes.

The older fathers were also twice as likely to have used assisted reproductive technology, including IVF, to conceive than their younger counterparts.

Dads are getting older

In this US study, the mean age of all fathers increased from 30.8 years in 2011 to 32.1 years in 2022.

In that same period, the proportion of men aged 50 years or older fathering a child increased from 1.1% to 1.3%.

We don’t know the proportion of men over 50 years who father children in Australia, but data shows the average age of fathers has increased.

In 1975 the median age of Australian dads was 28.6 years. This jumped to 33.7 years in 2022.

How male age affects getting pregnant

As we know from media reports of celebrity dads, men produce sperm from puberty throughout life and can father children well into old age.

However, there is a noticeable decline in sperm quality from about age 40.

Female partners of older men take longer to achieve pregnancy than those with younger partners.

A study of the effect of male age on time to pregnancy showed women with male partners aged 45 or older were almost five times more likely to take more than a year to conceive compared to those with partners aged 25 or under. More than three quarters (76.8%) of men under the age of 25 years impregnated their female partners within six months, compared with just over half (52.9%) of men over the age of 45.

Pooled data from ten studies showed that partners of older men are also more likely to experience miscarriage. Compared to couples where the male was aged 25 to 29 years, paternal age over 45 years increased the risk of miscarriage by 43%.

Older men are more likely to need IVF

Outcomes of assisted reproductive technology, such as IVF, are also influenced by the age of the male partner.

A review of studies in couples using assisted reproductive technologies found paternal age under 40 years reduced the risk of miscarriage by about 25% compared to couples with men aged over 40.

Having a male under 40 years also almost doubled the chance of a live birth per treatment cycle. With a man over 40, 17.6% of treatment rounds resulted in a live birth, compared to 28.4% when the male was under 40.

How does male age affect the health outcomes of children?

As a result of age-related changes in sperm DNA, the children of older fathers have increased risk of a number of conditions. Autism, schizophrenia, bipolar disorders and leukaemia have been linked to the father’s advanced years.

A review of studies assessing the impact of advanced paternal age reported that children of older fathers have increased rates of psychiatric disease and behavioural impairments.

But while the increased risk of adverse health outcomes linked to older paternal age is real, the magnitude of the effect is modest. It’s important to remember that an increase in a very small risk is still a small risk and most children of older fathers are born healthy and develop well.

Improving your health can improve your fertility

In addition to the effects of older age, some chronic conditions that affect fertility and reproductive outcomes become more common as men get older. They include obesity and diabetes which affect sperm quality by lowering testosterone levels.

While we can’t change our age, some lifestyle factors that increase the risk of pregnancy complications and reduce fertility, can be tackled. They include:

• smoking
• recreational drug taking
• anabolic steroid use
• heavy alcohol consumption.

Get the facts about the male biological clock

Research shows men want children as much as women do. And most men want at least two children.

Yet most men lack knowledge about the limitations of female and male fertility and overestimate the chance of getting pregnant, with and without assisted reproductive technologies.

We need better public education, starting at school, to improve awareness of the impact of male and female age on reproductive outcomes and help people have healthy babies.

For men wanting to improve their chance of conceiving, the government-funded sites Healthy Male and Your Fertility are a good place to start. These offer evidence-based and accessible information about reproductive health, and tips to improve your reproductive health and give your children the best start in life.

Karin Hammarberg, Senior Research Fellow, Global and Women’s Health, School of Public Health & Preventive Medicine, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

It’s a Saturday afternoon at a kids’ birthday party. Hordes of children are swarming between the spread of birthday treats and party games. Half-eaten cupcakes, biscuits and lollies litter the floor, and the kids seem to have gained superhuman speed and bounce-off-the-wall energy. But is sugar to blame?

The belief that eating sugary foods and drinks leads to hyperactivity has steadfastly persisted for decades. And parents have curtailed their children’s intake accordingly.

Balanced nutrition is critical during childhood. As a neuroscientist who has studied the negative effects of high sugar “junk food” diets on brain function, I can confidently say excessive sugar consumption does not have benefits to the young mind. In fact, neuroimaging studies show the brains of children who eat more processed snack foods are smaller in volume, particularly in the frontal cortices, than those of children who eat a more healthful diet.

But today’s scientific evidence does not support the claim sugar makes kids hyperactive.

The hyperactivity myth

Sugar is a rapid source of fuel for the body. The myth of sugar-induced hyperactivity can be traced to a handful of studies conducted in the 1970s and early 1980s. These were focused on the Feingold Diet as a treatment for what we now call Attention Deficit Hyperactivity Disorder (ADHD), a neurodivergent profile where problems with inattention and/or hyperactivity and impulsivity can negatively affect school, work or relationships.

Devised by American paediatric allergist Benjamin Feingold, the diet is extremely restrictive. Artificial colours, sweeteners (including sugar) and flavourings, salicylates including aspirin, and three preservatives (butylated hydroxyanisole, butylated hydroxytoluene, and tert-Butrylhdryquinone) are eliminated.

Salicylates occur naturally in many healthy foods, including apples, berries, tomatoes, broccoli, cucumbers, capsicums, nuts, seeds, spices and some grains. So, as well as eliminating processed foods containing artificial colours, flavours, preservatives and sweeteners, the Feingold diet eliminates many nutritious foods helpful for healthy development.

However, Feingold believed avoiding these ingredients improved focus and behaviour. He conducted some small studies, which he claimed showed a large proportion of hyperactive children responded favourably to his diet.

Flawed by design

The methods used in the studies were flawed, particularly with respect to adequate control groups (who did not restrict foods) and failed to establish a causal link between sugar consumption and hyperactive behaviour.

Subsequent studies suggested less than 2% responded to restrictions rather than Feingold’s claimed 75%. But the idea still took hold in the public consciousness and was perpetuated by anecdotal experiences.

Fast forward to the present day. The scientific landscape looks vastly different. Rigorous research conducted by experts has consistently failed to find a connection between sugar and hyperactivity. Numerous placebo-controlled studies have demonstrated sugar does not significantly impact children’s behaviour or attention span.

One landmark meta-analysis study, published almost 20 years ago, compared the effects of sugar versus a placebo on children’s behaviour across multiple studies. The results were clear: in the vast majority of studies, sugar consumption did not lead to increased hyperactivity or disruptive behaviour.

Subsequent research has reinforced these findings, providing further evidence sugar does not cause hyperactivity in children, even in those diagnosed with ADHD.

While Feingold’s original claims were overstated, a small proportion of children do experience allergies to artificial food flavourings and dyes.

Pre-school aged children may be more sensitive to food additives than older children. This is potentially due to their smaller body size, or their still-developing brain and body.

Hooked on dopamine?

Although the link between sugar and hyperactivity is murky at best, there is a proven link between the neurotransmitter dopamine and increased activity.

The brain releases dopamine when a reward is encountered – such as an unexpected sweet treat. A surge of dopamine also invigorates movement – we see this increased activity after taking psychostimulant drugs like amphetamine. The excited behaviour of children towards sugary foods may be attributed to a burst of dopamine released in expectation of a reward, although the level of dopamine release is much less than that of a psychostimulant drug.

Dopamine function is also critically linked to ADHD, which is thought to be due to diminished dopamine receptor function in the brain. Some ADHD treatments such as methylphenidate (labelled Ritalin or Concerta) and lisdexamfetamine (sold as Vyvanse) are also psychostimulants. But in the ADHD brain the increased dopamine from these drugs recalibrates brain function to aid focus and behavioural control.

Why does the myth persist?

The complex interplay between diet, behaviour and societal beliefs endures. Expecting sugar to change your child’s behaviour can influence how you interpret what you see. In a study where parents were told their child had either received a sugary drink, or a placebo drink (with a non-sugar sweetener), those parents who expected their child to be hyperactive after having sugar perceived this effect, even when they’d only had the sugar-free placebo.

The allure of a simple explanation – blaming sugar for hyperactivity – can also be appealing in a world filled with many choices and conflicting voices.

Healthy foods, healthy brains

Sugar itself may not make your child hyperactive, but it can affect your child’s mental and physical health. Rather than demonising sugar, we should encourage moderation and balanced nutrition, teaching children healthy eating habits and fostering a positive relationship with food.

In both children and adults, the World Health Organization (WHO) recommends limiting free sugar consumption to less than 10% of energy intake, and a reduction to 5% for further health benefits. Free sugars include sugars added to foods during manufacturing, and naturally present sugars in honey, syrups, fruit juices and fruit juice concentrates.

Treating sugary foods as rewards can result in them becoming highly valued by children. Non-sugar rewards also have this effect, so it’s a good idea to use stickers, toys or a fun activity as incentives for positive behaviour instead.

While sugar may provide a temporary energy boost, it does not turn children into hyperactive whirlwinds.

Amy Reichelt, Senior Lecturer (Adjunct), Nutritional neuroscientist, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.