Background: The aim of this study was to investigate whether physical activity (in general, and more specifically, walking and cycling during leisure time and for commuting purposes, sports and gardening) is an underlying mechanism in the relationship between the amount of green space in people's direct living environment and self-perceived health. To study this, we first investigated whether the amount of green space in the living environment is related to the level of physical activity. When an association between green space and physical activity was found, we analysed whether this could explain the relationship between green space and health.
Methods: The study includes 4.899 Dutch people who were interviewed about physical activity, self-perceived health and demographic and socioeconomic background. The amount of green space within a one-kilometre and a three-kilometre radius around the postal code coordinates was calculated for each individual. Multivariate multilevel analyses and multilevel logistic regression analyses were performed at two levels and with controls for socio-demographic characteristics and urbanicity.
Results: No relationship was found between the amount of green space in the living environment and whether or not people meet the Dutch public health recommendations for physical activity, sports and walking for commuting purposes. People with more green space in their living environment walked and cycled less often and fewer minutes during leisure time; people with more green space garden more often and spend more time on gardening. Furthermore, if people cycle for commuting purposes they spend more time on this if they live in a greener living environment. Whether or not people garden, the time spent on gardening and time spent on cycling for commuting purposes did not explain the relationship between green space and health.
Conclusion: Our study indicates that the amount of green space in the living environment is scarcely related to the level of physical activity. Furthermore, the amount of physical activity undertaken in greener living environments does not explain the relationship between green space and health.
There is increasing attention and evidence for a positive relation between the amount of green space in the living environment and people's health and well-being. Several studies have shown that a more natural living environment positively influences people's self-perceived health and leads to lower mortality risks (e.g.). However, little is known about the way in which green space exerts a beneficial effect on health. Several mechanisms may be underlying, of which the following are most commonly mentioned: recovery from stress and attention fatigue, encouragement of physical activity and facilitation of social contact. A large number of mainly experimental studies have produced strong evidence of the positive effect of nature on recovery from stress and attention fatigue. Less is known about other possible underlying mechanisms, such as physical activity. In this study we aim to investigate whether physical activity is a possible mechanism behind the relationship between green space and health.
It has long been known that being physically active has positive health effects. If a green living environment provides an incentive to be physically active, this could positively influence people's health. Literature shows that people are inclined to undertake physical activity in aesthetically appealing environments. Natural environments are perceived to be more aesthetically appealing than built-up environments. Therefore, natural environments may stimulate people to undertake healthy physical activities, such as walking or cycling, or to choose these activities as a mode of transport, and to spend more time on them.
Because of increasing urbanisation, combined with a spatial planning policy of densification, more people face the prospect of living in residential environments with fewer green resources. If the amount of green space in the living environment stimulates people to be physically active, the reduction of green space could have consequences for the amount of physical activity of the population.
Most of the literature concerning the relation between green in the living environment and the amount of physical activity focuses on specific types of physical activity, namely walking and cycling. Walking and cycling have been placed firmly on the public health agenda as a result of the awareness that health benefits could be derived by engaging in 30 minutes of moderate exercise every day. With regard to the influence of green space, a review of environmental influences on walking behaviour concludes that the aesthetic nature of the environment and accessibility of destinations, like parks and beaches, encourage walking. Pikora et al. (2003) concluded on the basis of available literature that attractiveness of the streetscape was one of the most important features related to walking and cycling. An attractive streetscape included, among other things, trees, wide grassy verges, parks, private gardens, diverse and interesting natural sights. These reviews mainly focused on research performed in Australia, the United States and the United Kingdom. Only a few studies have been performed on the relationship between the general level of physical activity and green space. A study by Ellaway et al. (2005) which used data collected in eight European countries showed that "for respondents whose residential environment contains high levels of greenery, the likelihood of being more physically active is more than three times as high, and the likelihood of being overweight and obese is about 40% less". However, on the other hand, a study by Hillsdon et al. (2006), conducted in the U.K., found no association between hours per week of recreational physical activity and access to and quality of any urban green spaces in a cohort of middle-aged adults.
Hoehner et al. (2005) and McGinn et al. (2007) both investigated the correlation between the presence of trees along the neighbourhood streets and physical activity. McGinn et al. found that those who perceived that lack of trees for shade was not a problem, or a barrier to physical activity were more likely to be active during leisure time physical activity. Hoehner et al., however, found no association between trees along the neighbourhood streets and transportation or recreational activity.
In the Netherlands, little support is found for a positive relationship between the amount of local green space and walking and cycling. Studies performed in the Netherlands show that the availability of local green space has little or no influence on how often people walk or cycle. In the case of poor availability of green space, people seem to walk and cycle more often in a built-up environment. For cycling, trips in the green environment tend to be longer than trips in the built-up environment. A study by Wendel-Vos et al. (2004) showed that the amount of green and recreational space, specifically sports grounds and parks, within a radius of 300 and 500 meters of the participants' homes was positively associated with time spent on bicycling in a Dutch city. According to Wendel-Vos et al. (2004), it is however likely that this reflects the fact that people living in the outskirts of towns spend more time bicycling to the city. A study by Den Hertog et al. (2006), performed in four different districts in Amsterdam, showed that a park of good quality in the district stimulates active behaviour, especially for children. However, people in the more urban neighbourhoods - neighbourhoods with less green space - appeared to be more physically active and were less often overweight. This was attributed to the design of the more urban districts, which had more facilities at walking or cycling distance and had no private parking space.
Besides the fact that a green environment can invite people to be physically active, it might also encourage people to exercise for longer periods of time. Research by Pennebaker & Lightner (1980) showed that joggers who jogged in a green stimulating environment were distracted from signals of fatigue and physical symptoms. Furthermore, research by Pretty et al. (2007) showed that people who participated in outdoor exercise programmes more often complete the programme than people who participated in indoor exercise programmes. These two studies imply that people engage in physical activity for longer periods in a green environment than in an indoor environment.
Overall, the available studies indicate that the evidence for a relationship between the amount of green space and the level of physical activity is limited. There are only indications for a positive relationship between an attractive streetscape and the amount of walking and cycling in Australia, the United States and the U.K. For other forms of physical activity and in other countries the available research is lacking or inconclusive. Furthermore, none of the described studies also link the possibly higher level of physical activity with people's health condition to see if the level of physical activity may be a mechanism underlying the relationship between green space and health.
It is interesting to investigate whether there is an association between green space and the level of physical activity particularly in the Netherlands, because of its strong walking and cycling culture in combination with its high degree of urbanisation.
The aim of this study was to investigate whether the relationship between green space and physical activity can be an underlying mechanism in the relationship between green space and self-perceived health in the Netherlands.
More specifically, the following research questions will be addressed:
Do people with a greener living environment more often meet the Dutch public health recommendations for physical activity?
Are people with a greener living environment more often physically active and do they spend more time on physical activity?
Can the amount of physical activity undertaken in greener living environments explain (part of) the relationship between green space and health?
Different types of physical activity which can take place in green areas will be considered. First of all, we will investigate whether people with more green space in their living environment more often meet the Dutch public health recommendations for physical activity, which states that people should engage in at least 30 minutes of moderate-intensity physical activity on at least 5 days per week. Furthermore, the following types of physical activity will be considered which can be conducted directly from the home and can be influenced by the amount of green space: walking and cycling (both during leisure time as well as for commuting purposes), sports (for instance running, inline-skating) and gardening.
The relationship will be analysed for different types of green space to discover which type of natural surroundings particularly promote the level of physical activity. Furthermore, the relationship is analysed for different levels of urbanicity. Urban areas are often characterised by limited green space and a high availability of facilities (e.g. shops, services) at walking and cycling distance. On the other hand, in rural areas there is lots of green space, but people often have to use the car to visit facilities. Finally, the relationship will be analysed for different age groups and different socio-economic groups, because it is hypothesized that the correlation is likely to be stronger for groups that spend more time in the vicinity of their homes: youth and the elderly and people with a lower socio-economic status.