Exposure to air pollution in early life could have lasting effects on child development and mental health in adolescence, according to our recent study.

We integrated air pollution data with existing longitudinal data from the Christchurch Health and Development Study (CHDS). The CHDS has followed more than 1,200 children born in the city in 1977, with a strong focus on developmental and mental health outcomes.

Our aim was to examine how exposure to air pollution shapes development and mental health in later childhood and adolescence. We found an increased risk of attention problems, conduct issues, lower educational attainment and substance abuse in adolescence associated with higher exposure.

Existing evidence often focuses on adulthood. However, by tracking air pollution exposure from the prenatal period to the age of ten, and linking this data to subsequent cognitive and mental health outcomes, we were able to highlight the long-term consequences of growing up in polluted environments.

Air pollution is one of the leading environmental contributors to disease, especially respiratory and cardiovascular conditions. Children are especially vulnerable to air pollution because their brains and bodies are developing.

A growing body of evidence suggests air pollution could affect brain development, educational attainment and mental health, contributing to depression, anxiety and conduct or attention problems. Despite this, few studies have tracked long-term exposure to air pollution from early childhood.

Patterns of exposure

We chose to conduct this research in Christchurch because the city is a historical air-pollution hotspot, with a documented history of measurements, and because of its long-running birth cohort study.

The CHDS collects detailed information on participants’ health, development, education and family backgrounds from prenatal into adulthood.

For this study, we linked historical air-pollution data, measured as the concentration of black smoke from 1977 to 1987, to residential locations of birth cohort members. This allowed researchers to estimate each child’s annual exposure to air pollution during key developmental periods.

We found four distinct patterns of air-pollution exposure across childhood (see graph below):

• consistently low (these children had the lowest levels of air pollution throughout childhood)
• consistently high (this groups had the highest levels of air pollution from birth to the age of ten)
• elevated preschool (exposure peaked between ages three to six and then declined)
• high prenatal and postnatal (high exposure before and immediately after birth, but declining later).

We then examined whether children in the higher exposure groups were more likely to experience adverse impacts on cognition, educational achievement and mental health in later childhood and adolescence.

We adjusted for a range potential confounders such as socioeconomic status, neighbourhood disadvantage and parental characteristics.

We found children with elevated pre-school exposure had poorer educational attainment and a higher likelihood of conduct disorders and substance abuse problems. High prenatal and postnatal exposure was linked to a greater risk of attention problems as well as substance abuse in adolescence.

Children with persistently high air-pollution exposure were more likely to develop attention problems and had higher odds of substance abuse issues in adolescence.

What these findings mean

The effects of air pollution on several outcomes were small at an individual level, but they could be highly important at a population level.

This is because even small shifts in cognitive and mental health outcomes, when applied to entire populations of children exposed to poor air quality, could have major consequences affecting future educational achievement, workforce productivity and public health burdens.

These findings support previous research suggesting air pollution could affect brain function by causing inflammation, oxidative stress and affecting neurodevelopmental pathways. Importantly, they reinforce the idea that certain developmental periods, such as the prenatal period and early childhood, may be especially sensitive to pollution exposure.

We need further research to confirm our findings but potential considerations include reducing children’s exposure to air pollution and improving urban air quality by cutting emissions from vehicles, industry and residential heating.

We should also promote cleaner energy sources to decrease exposure to harmful pollutants such as nitrogen dioxide and fine particulate matter. Providing better access to green spaces may mitigate the impact of air pollution.

To strengthen public health and policy measures, we need stricter air quality regulations, particularly around schools and childcare centres. We should also implement air-quality monitoring in urban areas to identify high-risk zones for children.

Better public information is crucial to minimise indoor and outdoor pollution exposure. This could include the use of air purifiers for indoor activies or limiting outdoor exposure during peak pollution periods.

Further research and action

Our study highlights the need for more research on air pollution’s effects on children’s mental health and cognition, particularly in different environmental and socioeconomic contexts.

Policymakers, educators and healthcare professionals must consider air pollution as a potential risk factor for developmental challenges, not just a physical health concern.

Air pollution may not be visible in the same way as poor housing or inaccessible healthcare, but its impact on child development could be important at a population level.

Given the rising prevalence of mental ill health in young people and adults, tackling air pollution could be an overlooked but essential public health strategy for protecting future generations.

Matthew Hobbs, Associate Professor and Transforming Lives Fellow in Spatial Data Science and Planetary Health, Sheffield Hallam University; Joseph Boden, Professor of Psychology, Director of the Christchurch Health and Development Study, University of Otago; Lianne Jane Woodward, Professor of Child Developmental Psychology, University of Canterbury, and Susie (Bingyu) Deng, Postdoctoral Research Associate in Health Sciences, University of Liverpool

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.