A new study from Washington State University found that people are more likely to live to 100 years old if they live in safe (and wealthy) neighborhoods with high levels of walkability.
The study analyzed the death records of 144,000 residents of Washington State, all over the age of 75, from 2011 to 2015, pooling information by gender, race, access to primary care physicians, and other measures. On balance, they found, a person's environment is one of the most influential factors when it comes to longevity.
Neighborhoods where there is an abundance of public infrastructure and places to walk to can help increase residents' lifespan, they found.
Being white was also "positively correlated with reaching centenarian status," as was being female and unmarried.
Study author Rajan Bhardwaj, a second-year medical student at WSU, who spent four years serving as a home aide to his grandfather, said he was inspired to do the study after wondering how his grandfather, who had underlying health conditions, still ended up living to 88.
"After we ran our analyses, I realized how many of the findings could help explain how my grandfather lived several years above the average lifespan in American even though he had poor health," Bhardwaj told Insider. "For example, living in walkable neighborhoods allowed him to get exercise, have easy access to medical care and grocery stores, and was an important way for him to socialize."
In 2015, there were half a million centenarians in the world, and that figure is expected to grow to eight times that by 2050. The life expectancy of humans has expanded considerably. In 1900, men could expect to live to 46 and women to 48. Now the current life expectancy for many Americans is 78 years.
But there's a lot researchers don't know about what influences life expectancy.
"Traditionally, we have believed that genetics plays a large role in aging," said Bhardwaj. "It is an important component, but research has consistently shown that environmental factors may be more significant contributors."
Those factors include diet, smoking, exercise, social support, socioeconomic status, access to medical care, walkability, and race. This study is one of the first to address research gaps on those environmental factors.
Previous studies have found that being female, married, living in urban areas, and having an active social life may have an effect on lifespan.
"This study really emphasizes the importance of socioeconomic status, and neighborhood walkability," said Christi Johnson, associate professor of Sport and Exercise Psychology at Cornell College. "I think that those two things are only now starting to get noticed in terms of our understanding of the relationship between health and longevity."
Johnson was surprised that the study found a positive association between being never-married, divorced, or widowed and living to 100, when compared to married people, who tended to die younger. This runs counter to a lot of research showing that living alone as a senior can be bad for one's health.
"For marriage, it was hard to provide a single theory for the findings we observed," Bhardwaj told Insider. "It has traditionally been thought that marital status is beneficial for health, but some research refutes that this is true in all cases."
The authors theorized that these single people did not have the increased stress of an unhealthy marriage, and the paper provides some data suggesting widowed people may have lost their spouses much earlier in life and may not experience the stresses associated with losing their partner. They noted that more research is needed in that area.
Johnson was also surprised the study found that educational attainment wasn't that big of a factor.
"The education piece might be less important than it was quite some time ago as we're seeing our population becoming more and more educated," said Johnson. "I wondered if the current value of a bachelor's degree is not the same as what it was in the 1950s."
Bhardwaj suggested that the findings might have to do with the fact that the subjects in the study were all 75 or older and education may have not been so strongly associated with health for this cohort.
56% of the participants were female, and 93% were white. The average participant age was 86 years, and 58% had high school diplomas.
The study noted that not being white, or being male, were both risk factors for dying before 100.
Only 1.8% of participants lived to be over 100, although one did live to 114.
"Another consistent finding in research is that certain minorities, particularly African Americans and Native Americans, don't live as long as White Americans," Bhardwaj said. "These findings are related to the large disparities these groups experience in factors such as socioeconomic status, disease incidence, incarceration, and education."
The study found being in a safe, walkable neighborhood is more conducive to having a longer life. That is more possible if you're white, thanks to the lingering effects of housing segregation, which make people of color more likely to live in unsafe, less walkable neighborhoods.
The study also found that white people tend to live longer, but like many other longevity studies, that may be because the vast majority of its participants were white.
"This is an indicator that health disparities do exist and they need to be taken very seriously," said Johnson. "It is notable that race is a significant factor here, and that being a person of color is likely to work against an individual in terms of longevity."
Bhardwaj noted that there needs to be more research on the root causes of these health disparities, so they could be addressed. According to the CDC, Black men and women have lower life expectancies than their white counterparts, and data shows the Black and Latinx communities are bearing the brunt of the effects of the COVID-19 pandemic. This makes research about health disparities more useful than ever.
"This study is a reminder to public health experts that it can't just be the individual choosing to be active, the community has to support that activity," said Johnson, "and the physical structure of the community has to support that activity as well."