How maternal and neonatal health could determine dementia risk decades later

Emerging evidence suggests that the risk of dementia may be traced back to factors present at birth. Low birth weight, premature delivery, perinatal complications, and maternal stress or nutritional deficiencies can subtly influence brain development, reduce cognitive reserve, and increase vulnerability to neurodegenerative disease later in life.

These early-life factors shape neural connectivity, brain structure, and long-term resilience, effectively ‘programming’ the brain decades before dementia manifests.

The developing brain is highly sensitive to its early environment. Factors such as low birth weight, preterm delivery, perinatal complications, maternal stress, and nutritional deficiencies can affect neural growth, connectivity, and cognitive reserve—the brain’s ability to compensate for damage over time.

Disruptions at these foundational stages may reduce the brain’s resilience, increasing the likelihood of cognitive decline and dementia in later life.

Dementia is a progressive condition marked by a decline in memory, thinking, reasoning, and the ability to carry out everyday activities.

It is not a single disease but a collective term for disorders such as Alzheimer’s disease and vascular dementia, all of which involve damage to brain cells and the gradual breakdown of communication between different parts of the brain.

Although dementia most often becomes apparent in older age, it is not a normal part of ageing. Rather, it develops slowly over many years as brain resilience diminishes.

Early foundations

Increasingly, scientists are recognising that the foundations of dementia risk may be laid much earlier in life, even during childhood or before birth. In early development, the brain grows rapidly, forming the neural connections that support learning, memory, and problem-solving throughout life.

When this process is disrupted by factors such as poor maternal nutrition, prenatal stress, low birth weight, premature birth, childhood illness, or prolonged stress and deprivation, the brain may develop with fewer neural connections or reduced cognitive reserve. Cognitive reserve refers to the brain’s ability to compensate for damage and adapt as it ages.

Children who experience malnutrition, limited stimulation, chronic stress, or poor health may not show immediate cognitive problems, but these early challenges can subtly shape brain structure and function.

Over time, this reduced resilience can make the brain more vulnerable to the effects of ageing, vascular disease, or neurodegenerative processes.

Dementia, therefore, does not suddenly begin in old age; it emerges as the culmination of lifelong influences on brain health, with roots that may stretch back to the earliest stages of life.

A study titled “Association of birthweight and risk of incident dementia”, published in GeroScience, notes that conditions around birth may influence dementia risk many decades later.

Using data from the UK Biobank, researchers followed 275,648 adults who were free of dementia at baseline for a median period of 13 years, tracking who went on to develop dementia.

Other Topics To Read

• Health
• Maternal Health
• dementia
• Alzheimer’s disease
• neonatal health
• Brain development
• birthweight
• cognitive reserve
• vascular dementia
• UK Biobank
• GeroScience
• How maternal and neonatal health could determine dementia risk decades later
• Headlines

Lower birthweight and higher risk

Participants self-reported their birthweight, which was then grouped into categories ranging from low to high. The study found a clear and consistent association between lower birthweight and a higher risk of developing dementia, particularly vascular dementia.

Individuals born weighing 2.95 kilograms or less had a significantly higher risk of incident dementia compared with those born in the mid-range birthweight category.

This association remained robust even after adjusting for a wide range of confounding factors, including age, sex, education level, socioeconomic status, smoking, physical activity, body mass index, and major cardiovascular conditions.

Importantly, the researchers did not find a simple linear relationship where “higher is always better.” Instead, the lowest dementia risk was observed among individuals born within a moderate birthweight range, suggesting that optimal fetal growth—rather than extreme size—is most protective for long-term brain health. Very high birthweight did not consistently confer additional cognitive benefits.

Beyond dementia diagnoses, the study also examined cognitive performance and brain imaging outcomes. Participants with lower birthweight performed worse on tests of memory, processing speed, and executive function, even before dementia onset.

Brain MRI data showed that lower birthweight was associated with smaller total brain volume and reduced volume in subcortical structures, regions that play a key role in memory and cognitive processing and are often affected early in dementia.

Why birthweight matters

The findings help explain why birthweight matters. Birthweight is widely used as a proxy for the quality of the intrauterine environment, reflecting maternal nutrition, placental function, exposure to stress or illness, and overall fetal growth.

Suboptimal conditions during this critical period may limit neuron development, synaptic density, and vascular integrity in the brain. These early constraints can reduce cognitive reserve, making the brain less able to compensate for age-related damage or disease later in life.

The stronger association observed with vascular dementia also suggests that early-life influences on blood vessel development and metabolic health may play a role.

Poor fetal growth has been linked to a higher lifetime risk of hypertension, diabetes, and cardiovascular disease—well-established contributors to dementia. In this way, early developmental disadvantage may set individuals on a long-term health trajectory that increases vulnerability to neurodegeneration.

Research from Sweden has shown that low birthweight and small head circumference are linked with up to double the risk of late-life cognitive impairment and dementia, even after accounting for familial, socioeconomic, and educational factors.

Each increment in birthweight and head size was associated with a reduced risk of dementia and cognitive dysfunction, underscoring the importance of healthy prenatal growth for building cognitive reserve.

A meta-analysis of multiple cohort studies indicates that women who experienced hypertensive disorders during pregnancy—such as preeclampsia or high blood pressure—had a roughly 38 per cent higher risk of later-life dementia compared with women without these conditions.

The risk for vascular dementia was particularly elevated, suggesting that pregnancy complications tied to vascular health may influence brain ageing in mothers as well.

Investing early

Additional research also highlights that early-life exposures—such as maternal smoking around birth and childhood growth patterns—are associated with higher dementia risk, emphasising how a broader set of prenatal and early-life environments may contribute to brain health decades later.

Understanding that dementia risk may begin before birth highlights the importance of investing in maternal and neonatal health as a form of brain health prevention.

This includes ensuring quality prenatal care, addressing maternal nutrition and stress, managing pregnancy complications, and offering supportive early-childhood development programmes.