Forests around the world are increasingly affected by factors related to climate change, along with industrialization and lifestyle changes. Among other consequences, this diminishes opportunities for human contact with nature and results in worse health outcomes. With the aim of reducing vulnerability to increasing threats from climate change as well as improving population health and well-being, China has implemented multiple measures since 2004 to improve forest management, including promoting the construction of National Forest Cities. 

National Forest Cities in China…

After approval of the national forestry authorities, a city can be awarded the title of National Forest City if both its urban and rural areas meet all the necessary criteria. These include urban forest coverage, greening along water bodies and roads, nature reserves and major forest and wetland ecosystems, as well as residential recreational greenspaces, which must be public and easily accessible (i.e. in close proximity to most citizens, within 500 meters, on average). By the end of 2022, there were 219 National Forest Cities in China in 25 provinces, forming a cross-regional and urban‒rural construction system.

Although intended primarily for environmental improvement, these forest cities also include sites and facilities that encourage physical activities. However, despite the rapid increase in research on environmental features and physical activity behaviors over the last few decades, there is still a lack of reliable empirical evidence on the effect of these forest cities on residents’ physical well-being. 

… and their effect on physical activity: a quasi-experimental study

We attempted to fill this knowledge gap in a recent paper (Tang et al 2024), using a difference-in-difference, or DID, model, which, in our case, focused on differences in the frequency of physical activity before and after the construction of the forest cities, comparing regions with different densities of forest cities. The DID model circumvents otherwise difficult-to-treat issues such as time trends and individual characteristics.

Our data come from the nationally representative 2010 China Family Panel Studies (CFPS), and its 2018 follow-up. This is a multistage, stratified cluster sampling representing 95% of the population in mainland China. Among other things, respondents were asked to specify the number of physical activities they had engaged in during the preceding week, which is our variable of interest.

Living in a forest city can be considered exogenous (it does not depend on individual choices), and we measured exposure to this exogenous intervention in terms of both degree (number of forest cities by area at the provincial level) and duration (time elapsed since the City was awarded the title of National Forest). This proved possible because respondents were interviewed in areas with different degrees of forest environment construction, as measured by the number of forest cities, and different construction timelines. During the survey windows (i.e. between 2010 and 2018), 11 provinces established 1-3 forest cities, 13 provinces established more than three, and the remaining six provinces did not establish any.

Results

The DID estimates revealed that forest environment construction significantly promotes residents’ physical activities. After the construction of forest cities, the number of physical activities per week increased by 1.35 units (β = 1.35, 95% CI: 0.73–1.98) compared to provinces without forest cities (Table 1). An increase of 1.35 may seem small, but first, it is statistically significant, even after adjusting for covariates such as age, area of residence, province, marital status, income, educational level, employment, chronic disease and self-rated health, and second, it represents a considerable step forward given the relatively low initial levels.

Perhaps not surprisingly, there were notable disparities across age groups and areas of residence. The positive effect of forest environment construction on physical activity was particularly strong among middle-aged and older adults (aged 45 and above), and people living in urban areas. 

Among younger adults aged (up to 44 years of age), the frequency of physical activity also increased after forest environment construction, but the difference was not statistically significant.

Behavioral changes facilitated by environmental construction

To the best of our knowledge, this study is the first to provide insights on the impact of forest environment construction on physical activity among Chinese residents. The main finding is that the construction of a forest environment promotes physical activity, especially among middle-aged and older adults, and people living in urban areas.

Although urbanization and land use change are irrevocably altering the environment in which many residents live, forest-environment construction has succeeded in reducing the distance between people and the natural environment and plays a role in improving population fitness. However, considering the heterogeneity of these effects, more should be done to make sure that everybody benefits from the construction of forest cities, for instance in terms advertising their existence and promoting their potential for “green exercise”.

References

Tang, H. M., Yuan, D. Q., Yang, P. S., Yang, H. B., & Guo, C. (2024) The effect of forest-environment construction on the physical activity among Chinese adults. Environmental Research Letters, 19.

The post Effects of forest environment construction on physical activity appeared first on N-IUSSP.

Shortly after the Tokyo Olympic Games, the Beijing Winter Olympic Games and Paralympic Games were held in February 2022. Previously, public health experts had expressed great concerns over the safety of the Tokyo Olympic Games amid the COVID-19 pandemic and appealed for a global conversation on this issue (The Lancet 2021).

Mass gatherings have potential risks, especially amid a global health crisis. However, the benefits of the Olympic Games may be wide-ranging, including economic growth, urban development and expansion of sports infrastructure. They may also help improve public health services and risk management, public health surveillance and reporting systems (e.g. of air quality), as well as individual health awareness and behaviours. Several previous studies have investigated the association between the Olympic Games and health outcomes such as exposure to respirable particulate matter, adolescent psychological health, and asthma, but apparently none have studied the long-term association between the Olympic Games and child growth.

Underweight and overweight among Chinese children. A triple difference-in-difference analysis

In a recent study (Guo et al., 2022), we estimated the association between the 2008 Beijing Olympic Games (BOG) and child growth in China. We used the BOG as a natural experiment to capture the potential long-term effect of the Olympic Games on child growth at the population level. Individual-level data were obtained from the China Family Panel Studies (CFPS). Children aged 3–10 years during the survey window in 2014 and in 2018 were pooled into a dataset and included for analysis.
Exposure to the BOG was measured by triple difference-in-difference analysis. First, children aged 7–10 years were identified as the treated group, as they were born either before the 2008 BOG (in 2004–2007) if surveyed in CFPS wave 2014, or after the BOG (in 2008–2011) if surveyed in wave 2018. Children aged 3–6 years were identified as the control group, as they were born after the 2008 BOG in both survey waves. The difference observed between two waves within the control group (D1) can be interpreted as a common temporal change, due, for example, to the general socio-economic development. Conversely, the difference between two waves within the treated group (D2) includes this common trend plus the effect of being born either before or after the 2008 BOG. This means that the variation “caused” by being born after the 2008 BOG and not before can be identified through the difference between the treated group and control group in the difference between two waves (D2–D1).

Additionally, although the Olympic Games is an event of national and even world significance, we assume that it affected mainly those living close to the venue of the Games and its surrounding areas. The host city of the 2008 BOG was Beijing, together with five mainland cities: Shanghai, Tianjin, Shenyang (Liaoning province), Qinhuangdao (Hebei province) and Qingdao (Shandong province), as co-host cities. (Hong Kong, the sixth co-host city, was not included in our analysis due to data limitations.) We thus categorised the areas of residence of our child participants into a binary variable: BOG areas or non-BOG areas. The rate of child growth is not the same at 3–6 years or at 7–10 years, and this is something that the D2–D1 estimator mentioned above does not control for. However, we can assume that the trend differential of the two groups of children is the same in BOG and in non-BOG areas. Thus, the association between the BOG and child growth can be identified through the difference between areas in difference between age groups in difference between waves: (D3–D2–D1), or DDD.

Child growth was assessed via four binary variables: stunting, underweight, overweight, and obesity. We generated standardising anthropometric measures for children including z-score of height-for-age (HAZ) and z-score of weight-for-age (WAZ) according to the WHO growth charts, and derived indices of stunting if HAZ ≤ 2 and underweight if WAZ ≤ 2, respectively. Furthermore, overweight and obesity were measured by binary variables according to the international body mass index (BMI) thresholds for children aged 2–18 years (BMI ≥ 25 for overweight and BMI ≥ 30 for obesity). 

The study included 6,951 Chinese children aged 3–10 years, among whom 3,201 were interviewed in 2014 and 3,750 in 2018. The pooled prevalence rates of stunting, underweight, overweight, and obesity were 7.8%, 26.4%, 14.10%, and 20.9% (Figure 1). 

The health(y) effects of 2008 Beijing Olympic Games

Our DDD estimates reveal that BOG exposure decreased the risk of underweight by 88% among Chinese children, and that of overweight by 58% (Figure 2). The effects of BOG on the odds of stunting and obesity were not statistically significant.

We did not detect sex heterogeneity of associations between the BOG and stunting, underweight or overweight. However, we did find a sex difference for the association between the BOG and child obesity, with a significantly lower risk of obesity found in the female, but not in the male sample. In girls, the risk of obesity was 21% (95% CI: 5%-88%) for those exposed to the BOG compared with those not exposed, after controlling for observable covariates.

Long-term health legacy planning before mega-events

To the best of our knowledge, this is the first attempt at estimating the effect of the Olympics on child growth. Our findings are that the 2008 Beijing Olympic Games decreased their risk of underweight and overweight, and, for girls only, also the risk of obesity. 

This may have happened through several potential mechanisms. First, children of the post-Olympic generation might have benefited from a variety of favourable conditions related to the Olympic Games during the fetal period. This may be because, according to the International Organizing Committee, the Games had a positive impact on several social, urban, environmental, and economic criteria, such air quality, food and water safety, regeneration of the physical environment, Anti-smoking measures and the development of venues and training facilities promoting mass sport. Second, the Games may have also prompted active participation in sports, at all levels and at all ages, among children born shortly after the Games and their families.

While the mechanisms may be unclear, and not necessarily replicable elsewhere in the world, the results, as highlighted by our DDD research design, seem clear enough: children’s health improved in China following the 2008 Beijing Olympic Games.

References

The Lancet. (2021). We need a global conversation on the 2020 Olympic Games. Lancet 397:2225. doi: https://doi.org/10.1016/S0140-6736(21)01293-9.

Guo, C., Hu, X., Xu, C., & Zheng, X. (2022) Association between Olympic Games and children’s growth: evidence from China. British Journal of Sports Medicine 56(19): 1110–1114. doi: 10.1136/bjsports-2021-104844.

The post Olympic Games help children grow up healthy appeared first on N-IUSSP.