The Proper Dose of Nature

There has been a lot of research on the importance of getting outdoors in a natural setting.  That research and the general feelings people have had on the subject for centuries has led to the creation of lots of parks and other opportunities to enjoy the outdoors.  We summed up those findings in our review of Health Parks Healthy People: the State of the Evidence 2015. Unfortunately that research hasn’t determined how much nature or how often one should get out in it for the best outcomes.  If we knew more about that,  cities, for example,  could  design parks to better supply what their residents need.  Further,  Doctors that are now prescribing nature to their patients would be better able to prescribe an appropriate dose.

 

Researching the Nature Dose Question

The Healthy Parks Healthy People publication came out of Australia and the Australians have now published a study that answers some of the questions about the proper dose of nature.  This new study quantifies the relationship between health results and the dose of nature in terms of intensity, frequency and duration.  To do that they asked 1538 residents of Brisbane, Australia about their health and where and how much exercise they got over the course of a week.  With this data they were able to identify the intensity of nature in terms of the vegetative complexity in the places the people exercised.  Since they learned directly from the people about health issues and the frequency and duration of their experiences, they were able to link all of this data together and draw some interesting conclusions:

• longer duration of individual nature experiences was significantly linked to a lower prevalence of depression and of high blood pressure.
• higher frequency of green space visitation was an important predictor for increased social cohesion.
• both duration and frequency showed a significant positive relationship with higher levels of physical activity.
• depression was reduced when reported green space visits were an average of 30 minutes or more and was reduced even more up to 75 minutes outdoors.
• there was a significant improvement in blood pressure with a minimum of 30 minutes,  but the researchers were not able to determine if more time is better.
• higher levels of nature relatedness (individual connection to nature) predicted greater feelings of social cohesion and higher levels of physical activity.
• nature intensity (vegetation complexity) showed no association with any of the health outcomes measured.
• there could be up to 7% fewer cases of depression and 9% fewer cases of high blood pressure if the entire sampled population met the minimum duration criteria of 30 minutes or more.

That last point is really key.  The cost of depression and high blood pressure is very high and includes doctor visits, hospitalizations, drugs and much more.  By making high quality nature experience available and getting people to use them regularly for as little as 30 minutes,  society as a whole would see a significant financial benefit as well as individual health benefits.

All the Details

The report is available for free from Nature.com’s Scientific Reports:  Shanahan, Danielle F.;Bush, Robert; Gaston, Kevin J.; Lin, Brenda B.; Dean, Julie; Barber, Elizabeth; Fuller, Richard A. Health Benefits from Nature Experiences Depend on Dose. Scientific Reports 6, Article number: 28551 

Conclusion

We already knew that nature is good for us.  Now we know that we need to partake of it 30 minutes or more at a time to start seeing some significant benefits.