TORONTO -- A new study out of the U.S. suggests a correlation between minimal greenspace in lower-income neighbourhoods and higher rates of COVID-19.

The study entitled 鈥淣ature inequity and higher COVID-19 case rates in less green neighbourhoods in the United States鈥� was published last week in the journal It analyzed two datasets that compared access to greenspace and COVID-19 case rates for zip codes in 17 states.

The researchers documented the extent of what they called 鈥渟tacked inequities,鈥� which in this case meant that lower-income and majority racialized communities have both more COVID-19 cases and less nature accessible to them in an urban setting.

The study also investigated whether there is an association between access to nature and COVID-19 rates after accounting for race, ethnicity, income and other variables 鈥� an association boosted by the data that contact with nature may play an important role in the body鈥檚 ability to fight infections by boosting what are known as 鈥渘atural killer鈥� or NK cells that attack and kill virally infected cells.

Researchers found that the majority of zip codes that were home to racialized communities had both higher COVID-19 rates and less access to greenspace. The study states that as of Sept. 30, 2020, zip codes with a racialized majority of residents had nearly twice as many COVID-19 cases per 100,000 people as majority-white zip codes.

Less green zip codes also had higher rates of COVID-19 cases, even after researchers adjusted for variables like population density, race and ethnicity, income, time elapsed since the first recorded COVID-19 case, age, and state.

Analysis and modelling in the study found a 4.1 per cent decrease in COVID-19 cases with just a 0.1 per cent increase in access to greenspace.

鈥淥ur research shows a stark example of how the COVID-19 pandemic can exacerbate existing inequity,鈥� said lead study author Erica Spotswood . 鈥淭he inequality in access to nature in U.S. cities has been shown to have many health effects, and now it looks like it also has had significant health implications during the COVID-19 pandemic.鈥�

The results show that COVID-19 has 鈥渋nflicted the greatest burden鈥� on communities that also face widespread inequity in nature access, the study states.

鈥淯sing ZIP code-scale data, we show that communities with the least access to nature had the highest case rates of COVID-19鈥e also show that inequity in access to greenness and parks is widespread in the United States,鈥� the study says. 鈥淭aken together, our results demonstrate that the pandemic has compounded the disadvantages in low-income areas and communities in colour already facing fewer acres of park available for recreation and less greenness.鈥�

Researchers posit in the study that access to greenspace might affect COVID-19 case rates, as greenspace helps the body fight the virus by boosting the NK cells, which in turn the study says are boosted by contact with nature.

鈥淭here鈥檚 actually a very clear possible explanation for nature having a protective effect against COVID-19,鈥� said study co-author Ming Kuo explained in the release. 鈥淲e know spending time in parks or woods boosts our 鈥楴atural Killer cells鈥� 鈥� our body鈥檚 troops for fighting viral infections 鈥� and that the greener a person鈥檚 residential area, the less likely they are to come down with viral infections of various kinds. Basically, when we鈥檙e exposed to a virus 鈥� any virus -- our Natural Killer troops try to squash it immediately, before it turns into a full-blown case or causes symptoms.鈥�

鈥淭his is true for all viruses we鈥檝e studied, so it would be no surprise for this to be true of the virus underlying COVID, as well,鈥� she continued. 鈥淧lus, scientists have discovered a whole host of other ways in which nature helps fight disease 鈥� by reducing stress, etc. So, it would actually be more puzzling if we found nature didn鈥檛 have a protective effect against COVID-19.鈥�

Another possible explanations for the correlation between nature and COVID-19, the authors state, is that higher air pollution and temperatures have previously been related to higher COVID-19 case rates, something that greenspace and nature helps mitigate and lack of greenspace and access to nature means people might socialize more indoors, where infection in close quarters may be more likely.

Researchers stated that the study demonstrated that inequity in nature access has implications for mental health and social interactions 鈥渄uring a period of profound social and economic upheaval and mental health distress.鈥�

The study authors state that short-term broadening of access to nature may help alleviate some of the distress associated with the pandemic and that recognizing the public health implications of nature inequity could help reframe nature access as critical infrastructure to assist with broader public health initiatives in the long-term.