Earlier research, he said, has estimated that heritable factors explain only about 20% to 35% of an individual's chances of reaching 100.
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"We know from previous research that you can modify, through behavior, your susceptibility to different diseases based on your genetics," explained Ofer Amram, the study's senior author and an assistant professor who runs WSU's Community Health and Spatial Epidemiology lab.
Although earlier studies found a correlation between environment and longevity, the researchers wrote, "there was a gap in knowledge as to the exact environmental and social factors that make for an environment that best supports living to centenarian age, which this study helped to address."
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For this latest study — published in the International Journal of Environmental Research and Public Health and based on Washington State mortality data —researchers looked at state-provided data about the deaths of nearly 145,000 Washingtonians who died at age 75 or older. The data, between 2011 and 2015. included information on each person's age and place of residence at the time of death, as well as their sex, race, education level and marital status.
The WSU team used data from the American Community Survey, Environmental Protection Agency and other sources to assign a value to environmental variables for each participant’s neighborhood. The variables included poverty level, access to transit and primary care, walkability, percentage of working age population, and air pollution. Subsequently, they conducted a survival analysis to determine which neighborhood and demographic factors were tied to a lower probability of dying before reaching 100.
The researchers found that neighborhood walkability, higher socioeconomic status and a high percentage of working age population (a measure of age diversity) were main factors in people living to reach 100.
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"These findings indicate that mixed-age communities are very beneficial for everyone involved," Bhardwaj said. "They also support the big push in growing urban centers toward making streets more walkable, which makes exercise more accessible to older adults and makes it easier for them to access medical care and grocery stores."
Amram added that neighborhoods that offer more age diversity tend to be in urban areas, where older adults are likely to experience less isolation and more community support.