Residential Block Greenness Linked to Lower Incidence of Six Cardiovascular Conditions
Article Summary
- Medicare residents who live on blocks with more tree cover had lower rates of heart disease, hypertension and stroke in a recent study.
- The study supports the idea that cardiovascular disease risk can be modified for older adults.
- The study could provide guidance for health-encouraging neighborhood design.
Medicare recipients who live on blocks of Miami-Dade County with the highest levels of “greenness” (tree cover) experienced a lower incidence of heart disease, hypertension and stroke over five years compared to others living on a block with the lowest level of greenness.
“We think that that trees, by virtue of bringing people outside, particularly here in the subtropical environment of Miami, may be a key mechanism,” said lead researcher Scott Brown, Ph.D., research associate professor of public health sciences at the University of Miami Miller School of Medicine. “The ability of trees to reduce the air temperature may increase the likelihood that Medicare beneficiaries are able to walk outside or perhaps even to engage in physical activity in and around their homes, such as gardening.”
The study findings were published online in the prestigious Journal of the American Heart Association.
Greenness Matters for Heart Health
Dr. Brown, senior author Jose Szapocznik, Ph.D., chair emeritus and professor of public health sciences at the Miller School, and their colleagues compared rates of acute myocardial infarction, atrial fibrillation, heart failure, ischemic heart disease, stroke/transient ischemic attack and hypertension among 229,034 Medicare beneficiaries 65 and older in the county. They studied combined rates of these conditions in 2011 versus 2016.
The researchers found significantly fewer new diagnoses of these conditions for residents on blocks within the top 33% of consistent greenness measured using satellite imagery compared to the lowest third. Medicare beneficiary information was matched to Census-level block data.
“The most surprising finding was that we are able to show effects over a five-year period in terms of reducing the incidence of cardiovascular disease,” Dr. Brown said. The study also supports the idea that cardiovascular disease risk can be modified “even for older adults after age 65. That’s one of the remarkable aspects of our findings.”
Building on Previous Research
The findings are actionable. They can guide county officials on which blocks have the greatest need for planting trees, Dr. Brown said, and support strategies to reduce the cutting down of trees. He and colleagues collaborated with Maria Nardi, M.Arch, the director of Miami-Dade Parks, Recreation and Open Spaces and a co-author of the study.
The study builds on prior work by Dr. Brown and colleagues. For example, an earlier cross-sectional study demonstrated that levels of greenness were associated with a lower prevalence of four cardiovascular diseases. Nardi was able to take those results and others to advocate for ongoing greening initiatives in Miami-Dade, including the planting of more than 200,000 trees since 2011.
Previously, Dr. Brown and colleagues linked greenness with a lower incidence of Alzheimer’s disease, greater cognitive reserve and with helping to treat or prevent depression.
More Research Needed
Despite numerous studies over the past decade, the precise protective mechanism of greenness remains “somewhat unknown,” Dr. Brown said. “We have speculated that, given the conditions on the ground here in Miami-Dade County, that we have urban heat island impacts, and trees reduce the ambient air temperature.”
The investigators would like to study longer-term impacts of greenness in older adults and are expanding their research beyond Miami-Dade County. They want to further validate findings that indicated people who did not move homes during the study benefited more from high greenness compared to those who changed addresses.
Two additional research projects will look at possible mechanisms for the positive effects of greenness, such as increased physical activity or reduced inflammation. Dr. Brown also credits collaboration with colleague Joanna Lombard, M.Arch., professor in the University of Miami School of Architecture, for the success of these studies.
Tags: cardiovascular, Cardiovascular Division, Dr. José Szapocznik, Dr. Scott Brown, greenness, heart failure, ischemic heart disease, myocardial infarction, stroke