Built environment and changes in blood pressure in middle aged and older adults
Introduction
Cardiovascular disease (CVD), a family of pathologies that includes hypertension, coronary heart disease, and stroke, is the leading cause of death worldwide (World Health Organization, 2003), including in the United States (Centers for Disease Control and Prevention, 2007a, Centers for Disease Control and Prevention, 2007b). It is also a major source of disability and ill health, and the associated social and economic costs are high (Centers for Disease Control and Prevention, 2007a, Centers for Disease Control and Prevention, 2007b, World Health Organization, 1997a). Although compelling evidence has identified a number of risk factors for CVD (Dishman, Washburn, and Heath, 2004), most of which are closely related to lifestyle (U.S. Department of Health and Human Services, 1996, World Health Organization, 1997b), there is relatively little research documenting the role that the built environment plays in influencing and/or moderating CVD risk.
Environmental characteristics, including aspects of urban form, neighborhood safety, social capital and food availability, have received increased attention as they are related to physical activity, obesity, mobility disability, and CVD (Berke et al., 2007, Clarke et al., 2008, Diez Roux, 2003, Ewing et al., 2003, Fisher et al., 2004, Frank et al., 2004, Frank et al., 2005, Gauvin et al., 2008, Li et al., 2005, Li et al., 2008, Li et al., 2009, Li et al., in press, Lopez, 2004, Maddock, 2004, Mehta and Chang, 2008, Mobley et al., 2006, Morland et al., 2006, Mujahid et al., 2008a, Mujahid et al., 2008b, Owen et al., 2007, Rundle et al., 2007). Evidence to date suggests that the built environment can either positively influence health behaviors or be a health stressor. For example, urban environment characteristics such as greater population density, more street connectivity (higher intersection density or walkability), and higher land use mix (i.e., the degree to which residences, businesses and green spaces are integrated within neighborhoods) are associated with more walking or bicycling activities (Berke et al., 2007, Li et al., 2005, Li et al., 2008, Owen et al., 2007, Saelens et al., 2003), as well as less obesity (Frank et al., 2005, Li et al., 2008, Li et al., in press). With respect to CVD risk, limited research has shown that people living in better land use mix areas tend to be associated with a lower probability of being hypertensive (Mujahid et al., 2008a, Mujahid et al., 2008b) and lower coronary heart disease risk (Mobley et al., 2006). Conversely, sprawling areas are likely to have a higher prevalence of hypertension (Ewing et al., 2003).
The aims of this study were to examine environmental characteristics that may influence, either directly or interactively, hypertension, an important component of CVD. We chose blood pressure because of its public health significance as a primary or contributing cause of death for Americans (Centers for Disease Control and Prevention, 2007a, Centers for Disease Control and Prevention, 2007b). To address the study aims, we first tested the general working hypothesis that neighborhoods with high walkability would be associated with reduced blood pressure values whereas neighborhoods with higher densities of fast-food restaurants would be associated with increased blood pressure over time. Next, we tested the moderating hypothesis that the effect of the density of fast-food restaurants on blood pressure would become weak or inconsequential when neighborhood walkability is high and residents within neighborhoods engage in healthy behaviors.
Section snippets
Study design and population
The study used a prospective, multilevel design. Residents aged 50–75 living in the Portland, Oregon metropolitan region's urban growth boundary (UGB) formed the population of the Portland Neighborhood Environment and Health study, which has been described in detail elsewhere (Li et al., 2008). From this sampling framework, 1221 participants were randomly recruited from a randomly selected sample of 120 Census block groups (a median of nine participants per neighborhood; range 5–21).
Results
Participants (656 males, 489 females) ranged in age from 50 to 75 years at baseline and had lived in their current residence for an average 8.5 years. Blood pressure in the study sample fell within the pre-hypertension category (120–139 mmHg systolic; 80–89 mmHg diastolic) per established guidelines (National Institutes of Health, 2008). At baseline, 37% of the participants reported use of blood pressure-related medication and the percentage increased slightly (38.5%) by the 1-year follow-up.
Discussion
Our findings indicate that low neighborhood walkability and high density of fast-food restaurants were both significantly related to increases in systolic and diastolic blood pressure over time. However, new findings from the current study point to the important role of neighborhood walkability in moderating the often-reported negative impact of fast-food availability on CVD risk, specifically hypertension. Our results show that for neighborhoods with low walkability, there is a strong
Implications
Our findings have important urban planning and public health implications. First, public health efforts aimed at reducing urban health risk need to focus on improving built environment features related to neighborhood walkability. Efforts to either increase connected street networks or maximize mixed land use would appear most beneficial for increasing neighborhood active living potential so that residents may become more physically active and, ultimately, reduce adverse health consequences
Study limitations and strengths
There are some limitations to this study. First, our blood pressure measures were taken during a single visit at both baseline and follow-up, which may entail potential measurement errors due to unmeasured confounders such as caffeine use, white coat hypertension or masked hypertension. Similarly, the use of self-reported physical activity and fruit and vegetable measures may also have introduced measurement biases. The use of objective measures (e.g., accelerometers) would allow us to assess
Conclusions
The current study adds to the nascent research on built environment and health by showing that neighborhood walkability, combined with residents' healthy behaviors, can reduce the impact of an unhealthy food environment on blood pressure. Findings suggest urban developers and designers, and health professionals must consider the built environment features of neighborhood walkability, such as mixed-land use and street connectivity, to create communities that positively impact hypertension by
Acknowledgments
The work presented in this paper is supported by a research grant from the National Institute of Environmental Health Sciences, National Institutes of Health (Grant #1R01ES014252).
Conflict of interest
The authors have no conflict of interest to declare.
References (39)
- et al.
Fat city: questioning the relationship between urban sprawl and obesity
J. Urban Econ.
(2008) - et al.
Obesity relationships with community design, physical activity, and time spent in cars
Am. J. Prev. Med.
(2004) - et al.
Linking objectively measured physical activity with objectively measured urban form: findings from SMARTRAQ
Am. J. Prev. Med.
(2005) - et al.
Built environment, adiposity and physical activity in adults aged 50–75
Am. J. Prev. Med.
(2008) - et al.
Weight status and restaurant availability: a multilevel analysis
Am. J. Prev. Med.
(2008) - et al.
Supermarkets, other food stores, and obesity. The atherosclerosis risk in communities study
Am. J. Prev. Med.
(2006) - et al.
Neighborhood walkability and the walking behavior of Australian adults
Am. J. Prev. Med.
(2007) - et al.
Evaluation of 2 brief instruments and a food-frequency questionnaire to estimate daily number of servings of fruit and vegetables
Am. J. Clin. Nutr.
(2000) - et al.
Association of the built environment with physical activity and obesity in older persons
Am. J. Pub. Health
(2007) Prevalence of heart disease — United States, 2005
MMWR
(2007)