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March 16, 2020

More green, more ‘zzzzz’? Trees may help us sleep

People in neighbourhoods with good tree cover are less likely to suffer from insufficient sleep, a new longitudinal study shows.

Not feeling sharp? Finding it hard to concentrate? About 12-19% of adults in Australia regularly don鈥檛 get enough sleep, defined as less than - hours each night. But who鈥檇 have thought the amount of tree cover in their neighbourhood could be a factor? Our has found people with ample nearby green space are much more likely to get enough sleep than people in areas with less greenery.

There鈥檚 plenty of on sleep, of course. Apart from personal routines, many other things can affect our sleep. and noise isn鈥檛 helpful. Other environmental factors at play include , and .

 

As a result of these factors and their interactions with others, such as age, occupation and socioeconomic circumstances, the chances of getting a decent night鈥檚 kip are across the population. So it is not simply a matter of personal responsibility and choosing to get more sleep.

Why does green space improve health?

We鈥檝e been studying the health benefits of green space for many years. We recently published that suggested more green space 鈥� and more tree cover in particular 鈥� could help reduce levels of cardiometabolic diseases like type 2 diabetes.

 

Why might green space be good for our health? We hypothesised that parks, woodlands and other nearby green spaces might actually help us to nod off. Green space might counter impacts of and , and cool local , all of which can make sleep difficult.

These benefits may be especially important in disadvantaged communities where many households might not have air conditioning and underlying health conditions can increase vulnerability.

Contact with nature can also provide opportunities for . It seems the benefits are greatest if there鈥檚 more and more (such as a richer variety of birdlife).

Our provided evidence of a link between green space and sleep duration in Australia. Since then, from various countries have reported similar results.

Importantly, most of this evidence comes from cross-sectional studies 鈥� 鈥渟napshots鈥� of a point in time. It鈥檚 a bit like trying to understand cause and consequence from a single photograph.

In this case, the 鈥渃hicken and egg鈥� concern with prior evidence is: does green space really support better sleep? Or could it be that people who already get better sleep, perhaps because they have fewer health issues or financial troubles, tend to live in greener neighbourhoods?

 

What鈥檚 new about our study?

Our addresses this concern. We investigated whether people with more green space within 1.6km had lower odds of developing insufficient sleep over about six years. They did not move home in this time.

We found 13% lower odds of developing insufficient sleep among people in areas where 30% or more of landcover within 1.6km had tree canopy, compared to people in areas with less than 10%. These results were consistent after taking into account factors that can influence both our sleep and access to neighbourhoods with more tree cover. These factors included age, sex, education, work status, marital status and household income.

 

Our findings help advance the quality of evidence for the influence of green space on sleep, but there鈥檚 more to be done. Importantly, some people may have 鈥渉ealthy鈥� sleep durations but still experience disturbed sleep and other sleep quality issues. While our evidence suggests more tree canopy may support healthier sleep duration, our future research will assess whether green space supports better-quality sleep.

Why does the tree canopy-sleep link matter?

Scientists around the world have found links between insufficient or poor sleep and poorer health, well-being and productivity.

 

Sleep-related problems affecting four in ten Australians cost an estimated A$40.1 billion in loss of well-being and A$26.2 billion in health system, productivity, informal care and other .

So public policies that improve our sleep by (re)shaping the urban environment could have important consequences for societies and economies.

While many people recognise the health benefits of green space, they overlook sleep. For example, the described many factors that influence sleep, but green space was not one of them.

The bottom line

We risk seriously undervaluing green space as an important source of natural capital in our cities if we assume we already know all the ways it benefits health. Some of these assumptions may not stand up to scrutiny. For example, a suggests the link between green space and lower diabetes risk might not be increased physical activity.

 

Some of the biggest health benefits of urban greening policies 鈥� such as the New South Wales Premier鈥檚 Priorities to increase and 鈥� might not be the most obvious. Nor can we assume health benefits will effortlessly materialise with more green space. An interesting in the US concluded use of portable electronic devices while in parks 鈥渟ubstantially counteracts the attention-enhancement benefits of green spaces鈥�.

This means how we engage with nature is important in determining how much health benefit we get in return. It highlights the need for equity-focused 鈥溾�� that enable people to regularly spend more time in urban parks and woodlands, if that鈥檚 what they鈥檇 like to do.

So there are yet more reasons to get out in the garden, take a restorative stroll in the woods, picnic in the park or rejoice in a botanic garden 鈥� and maybe improve your chances of a

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, Professor of Population Health and Environmental Data Science, NHMRC Boosting Dementia Research Leadership Fellow, and , Associate Professor in Urban Health and Environment; NHMRC Career Development Fellow,

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