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.

Intermittent fasting has become a popular dietary approach to help people lose or manage their weight. It has also been promoted as a way to reset metabolism, control chronic disease, slow ageing and improve overall health.

Meanwhile, some research suggests intermittent fasting may offer a different way for the brain to access energy and provide protection against neurodegenerative diseases like Alzheimer’s disease.

This is not a new idea – the ancient Greeks believed fasting enhanced thinking. But what does the modern-day evidence say?

First, what is intermittent fasting?

Our diets – including calories consumed, macronutrient composition (the ratios of fats, protein and carbohydrates we eat) and when meals are consumed – are factors in our lifestyle we can change. People do this for cultural reasons, desired weight loss or potential health gains.

Intermittent fasting consists of short periods of calorie (energy) restriction where food intake is limited for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a re-occurrence of the pattern rather than a “one off” fast.

Food deprivation beyond 24 hours typically constitutes starvation. This is distinct from fasting due to its specific and potentially harmful biochemical alterations and nutrient deficiencies if continued for long periods.

4 ways fasting works and how it might affect the brain

The brain accounts for about 20% of the body’s energy consumption.

Here are four ways intermittent fasting can act on the body which could help explain its potential effects on the brain.

1. Ketosis

The goal of many intermittent fasting routines is to flip a “metabolic switch” to go from burning predominately carbohydrates to burning fat. This is called ketosis and typically occurs after 12–16 hours of fasting, when liver and glycogen stores are depleted. Ketones – chemicals produced by this metabolic process – become the preferred energy source for the brain.

Due to this being a slower metabolic process to produce energy and potential for lowering blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and brain “fog”.

At the same time, as glucose metabolism in the brain declines with ageing, studies have shown ketones could provide an alternative energy source to preserve brain function and prevent age-related neurodegeneration disorders and cognitive decline.

Consistent with this, increasing ketones through supplementation or diet has been shown to improve cognition in adults with mild cognitive decline and those at risk of Alzheimer’s disease respectively.

2. Circadian syncing

Eating at times that don’t match our body’s natural daily rhythms can disrupt how our organs work. Studies in shift workers have suggested this might also make us more prone to chronic disease.

Time-restricted eating is when you eat your meals within a six to ten-hour window during the day when you’re most active. Time-restricted eating causes changes in expression of genes in tissue and helps the body during rest and activity.

A 2021 study of 883 adults in Italy indicated those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those eating without time restrictions.

3. Mitochondria

Intermittent fasting may provide brain protection through improving mitochondrial function, metabolism and reducing oxidants.

Mitochondria’s main role is to produce energy and they are crucial to brain health. Many age-related diseases are closely related to an energy supply and demand imbalance, likely attributed to mitochondrial dysfunction during ageing.

Rodent studies suggest alternate day fasting or reducing calories by up to 40% might protect or improve brain mitochondrial function. But not all studies support this theory.

4. The gut-brain axis

The gut and the brain communicate with each other via the body’s nervous systems. The brain can influence how the gut feels (think about how you get “butterflies” in your tummy when nervous) and the gut can affect mood, cognition and mental health.

In mice, intermittent fasting has shown promise for improving brain health by increasing survival and formation of neurons (nerve cells) in the hippocampus brain region, which is involved in memory, learning and emotion.

There’s no clear evidence on the effects of intermittent fasting on cognition in healthy adults. However one 2022 study interviewed 411 older adults and found lower meal frequency (less than three meals a day) was associated with reduced evidence of Alzheimer’s disease on brain imaging.

Some research has suggested calorie restriction may have a protective effect against Alzheimer’s disease by reducing oxidative stress and inflammation and promoting vascular health.

When we look at the effects of overall energy restriction (rather than intermittent fasting specifically) the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvement when participants followed a calorie restricted diet for 12 months.

Another study found a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study, which looked at the impact of calorie restriction on spatial working memory, found no significant effect.

Bottom line

Studies in mice support a role for intermittent fasting in improving brain health and ageing, but few studies in humans exist, and the evidence we have is mixed.

Rapid weight loss associated with calorie restriction and intermittent fasting can lead to nutrient deficiencies, muscle loss, and decreased immune function, particularly in older adults whose nutritional needs may be higher.

Further, prolonged fasting or severe calorie restriction may pose risks such as fatigue, dizziness, and electrolyte imbalances, which could exacerbate existing health conditions.

If you’re considering intermittent fasting, it’s best to seek advice from a health professional such as a dietitian who can provide guidance on structuring fasting periods, meal timing, and nutrient intake. This ensures intermittent fasting is approached in a safe, sustainable way, tailored to individual needs and goals.

Hayley O’Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University

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