Neural tube defect burden across the urbanisation gradient in 204 countries, 1990–2023: a cross-national ecological analysis of the Global Burden of Disease Study 2023
This cross-national ecological analysis of 204 countries from 1990 to 2023 reveals that neural tube defect burdens decline more rapidly in highly urbanized nations, yet demonstrates that targeted nutritional interventions, exemplified by China's 2009 folic acid policy, can achieve in a decade the reduction in disease burden that would otherwise require generations of urbanization-driven progress.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every year, hundreds of thousands of pregnancies are affected by neural tube defects, a group of serious birth conditions where a baby's brain or spine does not form correctly before birth. These conditions, which include severe forms like spina bifida and anencephaly, are among the most common causes of newborn death and lifelong disability worldwide. While the medical world has long known that taking folic acid—a B vitamin found in leafy greens and fortified foods—before conception can prevent most of these defects, the reality on the ground is uneven. In some places, fortified flour and prenatal vitamins are standard, but in others, these simple tools remain out of reach. This leaves a critical question: does where a person lives, specifically whether they live in a city or a rural area, determine whether their child is at risk?
A new study published in 2026, drawing on three decades of global health data, set out to answer this by looking at the world through the lens of urbanization. Researchers examined records from 204 countries and territories between 1990 and 2023, grouping nations by how much of their population lives in cities. They wanted to see if the gap between city and country was shrinking or growing, and whether the natural shift toward city living was enough to solve the problem on its own. The findings reveal a stark reality: the burden of these birth defects follows a clear path, with the least urbanized nations carrying the heaviest load. However, the study also uncovered a powerful exception that challenges the idea that we must wait for cities to grow to save lives.
The researchers began by sorting every country into five groups, from the least urbanized to the most. In 1990, the difference was already dramatic. In the least urbanized group, the rate of these defects was roughly double that of the most urbanized group. Over the next thirty years, rates fell everywhere, but the gap did not close. By 2023, the least urbanized countries still had rates more than twice as high as the most urbanized ones. The data shows that while living in a city generally offers better access to healthcare, fortified foods, and health education, simply waiting for a country to become more urbanized is a slow and incomplete strategy. In fact, the decline in the most urbanized nations happened faster than in the least urbanized ones, meaning the health gap between city and country actually widened over time.
The study then turned its attention to a specific natural experiment: China. For decades, northern China suffered from some of the highest rates of neural tube defects in the world. In 2009, the Chinese government launched a massive program to provide free folic acid supplements to every rural woman planning a pregnancy. The results were immediate and profound. Before the program, the country's rates were rising slightly. After the program began, the numbers plummeted. By 2023, China had reduced its burden by more than 93 percent, a drop so steep it stands alone in the global data. This rapid decline happened in just over a decade, a timeframe that would have taken generations of urbanization to achieve naturally. The researchers found that the timing of this drop matched perfectly with the start of the government program, suggesting that a targeted nutritional intervention can achieve in a few years what decades of economic development might otherwise take.
Despite this success, the global picture remains challenging. The study identified that in 2023, the countries with the highest rates of these defects were still concentrated in the least urbanized parts of the world, particularly in Sub-Saharan Africa and parts of South Asia. Countries like Afghanistan, Haiti, and the Central African Republic still face rates far higher than the global average. The researchers calculated that if the least urbanized countries had managed to reduce their rates as quickly as the most urbanized ones did over the last thirty years, nearly 300,000 extra cases of disability and death could have been avoided in 2023 alone. The countries that would have seen the biggest gains include Nigeria, Bangladesh, and the Democratic Republic of the Congo.
The analysis also highlighted that urbanization alone is not a magic shield. Some countries with high urbanization rates still struggle with high defect rates because they lack mandatory food fortification laws. Conversely, some nations with moderate urbanization saw their rates rise or stall because they failed to maintain consistent health programs. This suggests that the advantage of city living comes not from the concrete and buildings themselves, but from the systems they support: reliable food supply chains that carry fortified flour, clinics that offer prenatal screening, and health workers who can distribute supplements. Without these systems, even a city dweller remains at risk.
Looking ahead, the study projects that global rates will continue to fall, but the pace will likely remain slow for the poorest nations unless specific interventions are adopted. The authors argue that the Chinese model offers a clear path forward for other low-urbanization countries. By using existing community health networks to distribute free supplements directly to women planning pregnancy, nations can bypass the need for complex industrial food systems or decades of urban growth. The data suggests that this approach is not just a temporary fix but a scalable strategy that can dramatically reduce the global burden of these preventable conditions. The story of neural tube defects is no longer just about waiting for the world to change; it is about how targeted, simple actions can change the world for the next generation.
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