Living in greener neighborhoods is associated with lower risk of metabolic syndrome

Living in neighborhoods with higher levels of green vegetation is associated with a significantly lower risk of developing metabolic syndrome. New research indicates that this protective effect is largely driven by cleaner air, higher vitamin D levels, and increased physical activity. These findings were published in the scientific journal Environmental Research.

Metabolic syndrome is a serious health condition that affects a growing number of adults worldwide. It is not a single disease but rather a cluster of risk factors that occur together. These factors include high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels.

When a person has three or more of these conditions, they are diagnosed with metabolic syndrome. This diagnosis indicates a much higher risk of developing heart disease, stroke, and type 2 diabetes. As global populations shift toward urban living, the prevalence of these metabolic issues has risen.

City environments often contribute to sedentary lifestyles and expose residents to higher levels of air pollution. Both physical inactivity and pollution are known contributors to chronic disease. Public health experts have sought to understand how modifying urban environments might mitigate these risks.

Previous scientific inquiries have suggested that access to nature can improve health outcomes. However, the specific mechanisms driving this relationship remain under investigation. It has been unclear whether the benefits come from exercise, stress reduction, or environmental factors like air quality.

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“While there is growing evidence that exposure to residential greenspace is beneficial for adult health and well-being, we don’t really know how greenspace works to confer such health benefits. This study was motivated by the need to fill this research gap, with a specific focus on examining independent and multiple pathways, including biological, behavioral, environmental, and social factors, linking greenspace to adult metabolic health,” explained study author Chinonso Christian Odebeatu of The University of Queensland.

The researchers utilized data from the UK Biobank, a large-scale biomedical database. The analysis included 221,028 adults from across the United Kingdom. The participants had an average age of approximately 56 years at the time of recruitment.

To assess metabolic health, the team analyzed physical measurements and blood samples collected from the participants. They defined metabolic syndrome based on the Harmonized National Cholesterol Program criteria. A participant was classified as having the syndrome if they met three or more specific benchmarks regarding waist circumference, triglycerides, cholesterol, blood pressure, or glucose.

The study employed two distinct methods to measure exposure to greenspace. The first method involved the Normalized Difference Vegetation Index (NDVI). This uses satellite imagery to measure the density of living, green vegetation within a 500-meter radius of a participant’s home.

The second method utilized detailed mapping data to identify specific types of land use. This allowed the researchers to calculate the percentage of land dedicated to private residential gardens or public parks. This distinction provided a more nuanced view than satellite imagery alone.

The research team also gathered data on potential mediating factors. They assessed physical activity levels, sedentary behavior, and sleep patterns. They incorporated estimates of air pollution, specifically nitrogen dioxide and particulate matter, for each residential address.

Biomarkers such as serum vitamin D levels were measured from blood samples. Social factors were also considered, specifically self-reported feelings of loneliness. The researchers used statistical models to analyze the relationship between these environmental exposures and metabolic syndrome.

The results indicated a strong association between overall residential greenness and better metabolic health. Individuals living in areas with higher NDVI scores had significantly reduced odds of having metabolic syndrome. specifically, higher greenness was linked to a 29.3 percent lower likelihood of the condition.

This protective association was evident for several specific components of the syndrome. Higher greenness correlated with a lower risk of having a large waist circumference. It was also linked to healthier levels of triglycerides and lower systolic blood pressure.

The study did not find the same protective benefit for private residential gardens. The percentage of land covered by private gardens showed no significant association with metabolic syndrome in the overall analysis. This suggests that the total amount of vegetation may be more important than owning a garden.

A key objective of the study was to understand how greenspace provides these benefits. The researchers conducted a mediation analysis to estimate the contribution of different pathways. They found that nearly half of the protective effect of greenness could be explained by the identified mediators.

Reduction in air pollution emerged as the most significant pathway. Green vegetation acts as a buffer against pollutants, particularly nitrogen dioxide, which is often emitted by traffic. The study suggests that by lowering exposure to these harmful gases, greenspace reduces inflammation and metabolic stress.

Vitamin D levels also played a substantial role. Participants in greener areas tended to have higher levels of vitamin D. This is likely because attractive outdoor environments encourage people to spend more time outside, exposing them to sunlight.

“It was quite surprising and interesting to see vitamin D emerge as one of the key pathways linking greenspace to adult metabolic health, an important finding that, to our knowledge, has not been previously reported,” Odebeatu told PsyPost. “This opens new avenues for research into how behavioural, environmental, and biological pathways interact to shape health outcomes.”

Physical activity and reduced sedentary time were also identified as contributing factors. Greener neighborhoods may provide more inviting spaces for walking and recreation. However, the impact of physical activity was less pronounced than the impact of air quality and vitamin D.

The researchers also observed that the benefits of greenness were not uniform across all demographic groups. The association between greenness and reduced metabolic risk was stronger for men than for women. It was also more pronounced in adults aged 51 to 60 compared to younger or older age groups.

Socioeconomic factors influenced the strength of the association as well. The protective effects of general greenness were strongest for individuals living in more deprived neighborhoods. This suggests that public greenspace may be particularly valuable for communities that lack other health resources.

Conversely, private gardens only showed a protective effect for individuals in less deprived areas. This might reflect differences in how gardens are used or maintained in different socioeconomic contexts. It implies that simply having a garden space does not guarantee health benefits for everyone.

“Greenspace exposure has the potential to improve multiple aspects of adult health and well-being by facilitating increased physical activity and reduced sedentary behavior (e.g., driving, watching TV), enhancing vitamin D synthesis, lowering exposure to environmental air pollution, and alleviating loneliness through social connection,” Odebeatu said. “Therefore, spending time in nearby greenspaces may be a simple, natural way to support long-term health benefits.”

The study has some limitations. The research used a cross-sectional design, meaning data was collected at a single point in time. This prevents the researchers from definitively proving that greenspace causes better health, only that they are related.

Additionally, the air pollution data was modeled for the year 2010. While pollution levels are generally stable, this single-year estimate may not perfectly reflect long-term exposure for every participant. The study also focused on residential addresses and did not account for greenspace exposure at work.

“We need to clarify that not all greenspaces confer the same health benefits, as factors such as type, accessibility, and quality of greenspaces all seem to play a role in how much benefit one derives from such exposure,” Odebeatu said. “Additionally, while our findings suggest greenspace can reduce metabolic risk, these effects are modest at the individual level and should be seen as one component of a broader strategy for maintaining metabolic health. Finally, as this study is observational, we cannot establish definitive causality, and unmeasured factors may also influence the observed relationships.

Future research could address these gaps by following participants over many years. Longitudinal studies would help establish the timeline of how environmental changes impact metabolic health. Tracking exposure to nature throughout the day, rather than just at home, would also provide a complete picture. The researchers also recommend qualitative research to understand how people interact with their local environments.

“The present study provides quantitative evidence on the association and pathways between residential greenspace exposure and adults’ metabolic health,” Odebeatu explained. “The next line of research would be to incorporate qualitative research, which can provide rich insights into how people experience and interact with greenspaces.”

“For instance, qualitative evidence exploring how individuals perceive, use, and value different greenspace types may help explain why certain greenspaces appear to be more beneficial than others. It could also help identify barriers (e.g., safety concerns, mobility limitations, norms, etc) that quantitative data alone cannot capture.”

The study, “Residential greenspace indicators and metabolic syndrome in the UK Biobank Cohort: mediation through behavioural, environmental, social and biomarker pathways,” was authored by Chinonso Christian Odebeatu, Darsy Darssan, Charlotte Roscoe, Simon Reid, and Nicholas J. Osborne.