Associations of types of green space across the life-course with blood pressure and body mass index

Highlights

• We assessed sensitive periods of green space exposure and cardiometabolic health.

• Influence of types of green space on blood pressure and obesity is also examined.

• Proximity to parks at birth was associated with lower adult blood pressure.

• Birth may be a susceptible period for green space exposure and hypertension risk.

• Green space exposure across the life-course was not associated with BMI.

Abstract

Green space has been associated with better health and well-being. However, most studies have been cross-sectional with limited long-term exposure data. Further, research is limited in what type of green space is beneficial for health. We conducted a longitudinal study to assess sensitive periods (birth, childhood or adulthood) of exposure to different types of green space in association with adult blood pressure and body mass index (BMI). Using longitudinal data from the New England Family Study (1960–2000) and multilevel regression analysis, we examined associations between time-varying markers of residential exposure to green space, and adult BMI, systolic (SBP) and diastolic blood pressure (DBP) (N = 517). We created three exposure metrics: distance, average area, and green space count in the neighborhood throughout the life-course. In adjusted models, living one mile farther away from a green space at birth was associated with a 5.6 mmHg higher adult SBP (95%CI: 0.7, 10.5), and 3.5 mmHg higher DBP (95%CI: 0.3, 6.8). One more green space in the neighborhood at birth was also associated with lower DBP (−0.2 mmHg, 95%CI: −0.4, −0.02) in adulthood. Finally, average area of green space was not associated with SBP, DBP nor BMI. Analysis by type of green space suggested that parks may be more relevant than playgrounds, cemeteries or golf courses. Our study suggests that the perinatal period may be a critical time-period where living closer to green spaces may lower hypertension risk in adulthood, but not obesity.

Introduction

Green space has been linked to a wide range of favorable health outcomes including improved mental health (Shanahan et al., 2016), reduced blood pressure (de Blasio, 2016), better self-perceived general health (Kardan et al., 2015), lower risk of adverse pregnancy outcomes (Fong et al., 2018a), and lower risk of overall and cardiovascular mortality (Gascon et al., 2016). Exposure to natural environments or green space may benefit human health by reducing harm (mitigating exposures to heat, noise, and air pollution), relieving psychological stress, and/or promoting healthful activities such as exercise (James et al., 2015). These mechanisms may be particularly relevant in early-life since increasing physical activity levels is a crucial approach to control increases in childhood obesity as well as preventable lifestyle-related diseases, such as hypertension (Young, 2004). Moreover, evidence from longitudinal and cross sectional studies suggests that physically active children are more likely to be physically active in adulthood (Telama et al., 2005) and overweight/obese children are more likely to be overweight/obese adults (Starc and Strel, 2011). However, the cross-sectional nature of most prior studies on green space hampers the ability to identify long-term impacts and sensitive periods in which an exposure may have a larger association than the same exposure during other periods (Kuh, 2004).

In addition, high blood pressure (BP) and obesity are major risk factors for cardiovascular disease (CVD) (Mokdad et al., 2003). Adults diagnosed as obese (Body Mass Index - BMI ≥30 kg/m2) or overweight (BMI = 25–29.9 kg/m2) are at higher risk of CVD, compared with those of a normal weight (Arnett et al., 2019). In the US, hypertension (defined as systolic blood pressure [SBP] ≥130 mm Hg or diastolic blood pressure [DBP] ≥80 mm Hg) accounts for more CVD deaths than any other modifiable CVD risk factor (Arnett et al., 2019). Research has shown that atherosclerosis, the leading cause of CVD begins in childhood and that the extent of atherosclerotic change in children and young adults is associated with the presence of atherosclerotic risk in adults (Berenson et al., 1998). Therefore, it is useful to study the lifelong health impacts of modifiable determinants, such as green space, in early stages of life where public health interventions can be implemented to improve cardiovascular health in adulthood.

We used longitudinal data to evaluate the association between distinct measures of residential exposure to green space at birth, childhood, and adulthood, and two leading CVD risk factors at adulthood, BP and BMI as a marker of obesity. To our knowledge, this is the first longitudinal investigation of critical stages of exposure to green space across the life-course. Our objectives were first to assess which sensitive period (birth, childhood or adulthood) might have larger associations with blood pressure and body mass index, and second to compare three distinct measures of exposure to types of green spaces (closest distance, count or average area of the neighborhood green space).