Does change in the neighborhood environment prevent obesity in older women?

Highlights

• Changes to modifiable aspects of the neighborhood environment may reduce obesity.

• Most studies of the influence of neighborhood environment are cross-sectional.

• Portland region's changes to physical environment offer unique research opportunity.

• Change in neighborhood built environment was not associated with BMI in older women.

• Greater neighborhood SES protected against an age-related decline in BMI over time.

Abstract

Neighborhood environment is consistently associated with obesity; changes to modifiable aspects of the neighborhood environment may curb the growth of obesity in the US and other developed nations. However, currently the majority of studies are cross-sectional and thus not appropriate for evaluating causality. The goal of this study was to evaluate the effect of a neighborhood-changing intervention on changes in obesity among older women. Over the past 30 years the Portland, Oregon metropolitan region has made significant investments in plans, regulatory structures, and public facilities to reduce sprawl and increase compact growth centers, transit-oriented development approaches, and green space. We used geocoded residential addresses to link data on land-use mix, public transit access, street connectivity, and access to green space from four time points between 1986 and 2004, with longitudinal data on body mass index (BMI) from a cohort of 2003 community-dwelling women aged 66 years and older. Height and weight were measured at clinic visits. Women self-reported demographics, health habits, and chronic conditions, and self-rated their health. Neighborhood socioeconomic status was assessed from census data. Neighborhood walkability and access to green space improved over the 18-year study period. On average there was a non-significant mean weight loss in the cohort between baseline (mean age 72.6 years) and the study's end (mean age 85.0 years). We observed no association between neighborhood built environment or change in built environment and BMI. Greater neighborhood socioeconomic status at baseline was independently associated with a healthier BMI at baseline, and protected against an age-related decline in BMI over time. BMI decreases with age reflect increased frailty, especially among older adults with complex morbidities. Future research should consider the influence of the neighborhood environment on additional relevant health outcomes and should include measures of the social environment in conjunction with built environment measures.

Introduction

The impact of neighborhood environmental determinants on health may increase as adults age. As retirees spend more time near home, physical and mental health decline, and social supports decrease (Johnson and Troll, 1994, Shaw et al., 2007), older adults may grow increasingly dependent on their residential neighborhood. A review of the literature on neighborhood effects among older adults suggested that neighborhood environment can be a primary influence on older adults' health and functioning (Yen, Michael, & Perdue, 2009).

Increasingly, research is investigating the role of neighborhood built environment in physical activity and obesity (Ding & Gebel, 2012). Results from studies conducted in the general adult population suggest a protective effect of walkable neighborhood environments on obesity although interpretation is complicated by limitations in the design and execution of the studies (Feng, Glass, Curriero, Stewart, & Schwartz, 2010). Research specific to older adults is more limited (Kerr, Rosenberg, & Frank, 2012). While prior cross-sectional studies evaluating environmental correlates of obesity in samples of older adults support a significant association between neighborhood environment and BMI or other measures of obesity (Berke et al., 2007, Eisenstein et al., 2011, Frank et al., 2010, Grafova et al., 2008, James et al., 2013, King et al., 2011; Lee et al., 2009, Li et al., 2008), results from longitudinal studies are mixed, with studies suggesting no association, a positive association, and a negative association between BMI and characteristics of the built environment (Lee et al., 2009, Li et al., 2009, Michael et al., 2013, Sarkar et al., 2013).

Any study examining weight change in a cohort of older adults (in our study, adults 72–85 years) must consider two different outcomes: obesity and weight loss. Walkable neighborhood environments may prevent obesity. Approximately 35% of Americans aged 60 years and older are now overweight or obese (Flegal, Carroll, Ogden, & Curtin, 2010), and older women are more likely to be obese (13%) than are older men (12%) (Flegal et al., 2010). The prevalence of obesity in adults aged 60 and over increased about 35% between 1990 and 2000 (Arterburn et al., 2004, Villareal et al., 2005); since 2000 the increase has stabilized in older women, but continues to rise in older men (Flegal et al., 2010). Unhealthy body weight is strongly linked to poor health outcomes in older adults (Colditz et al., 2004, Grundy, 2000), including increased risk of chronic diseases such as diabetes mellitus (Apovian et al., 2002), coronary heart disease (Grundy, 2000, Vincent et al., 2010), and breast cancer (Colditz et al., 2004). Obesity also increases the risk of disability (Vincent et al., 2010) and is associated with lower overall quality of life among older adults (Yan et al., 2004).

Alternatively, neighborhood walkability may result in attenuation of weight loss in older adults. Despite the increased prevalence of obesity among older adults, weight and BMI generally increase until age 60 and then remain stable (Villareal et al., 2005). Over age 75, weight loss is a marker of frailty (Fried, Ferrucci, Darer, Williamson, & Anderson, 2004). Modest levels of physical activity may attenuate aging-related weight loss because exercise for this age group keeps them stronger and healthier, rather than reducing BMI (Dziura et al., 2004, Stephen and Janssen, 2010). A recent study found that modest amounts of physical activity attenuated age-related weight loss by approximately 25% in a normal healthy cohort of adults aged 65 years and older (Stephen & Janssen, 2010).

Another major challenge related to interpreting evidence of the influence of the neighborhood environment on weight change is the difficulty in establishing a causal association (Ding & Gebel, 2012). Cross-sectional studies represent the most common source of evidence and do not account for temporal precedence. Neither do these studies generally consider competing explanations of the built environment–physical activity relationship, most importantly neighborhood self-selection: as people may select their residence based on a preference to be active, residential selection may inflate or over-estimate the causal influence of neighborhood features on residents' BMI (Smith et al., 2011, Zick et al., 2013).

Evaluation of natural experiments, including opportunistic evaluations of environmental interventions, are recommended to enhance causal inference (Ding & Gebel, 2012). While some studies have evaluated changes in neighborhood environment as a result of individuals moving, these studies have methodological limitations including self-selection, small samples of movers, short follow-up periods, and focus on movers to new housing developments (Giles-Corti et al., 2013; Lee et al., 2009). Studies examining impacts of changes to neighborhood design provide a stronger test of the influence on obesity (Durand, Andalib, Dunton, Wolch, & Pentz, 2011).

Over the past 30 years, the Portland region and the state of Oregon have made significant investments in plans, regulatory structures, and public facilities to reduce sprawl. The region is governed by Metro, a chartered regional government with elected officials. In December 1994 Metro adopted the Metro 2040 Growth Concept, in which city and county growth plans were required to incorporate such strategies as: (1) compact growth centers, (2) affordable housing, (3) open space development, and (4) transit-oriented development approaches. The light rail system in Portland, significantly expanded during the past decade, is intended not so much as a replacement for cars but as an intervention to increase active modes of transportation, including walking. Additionally, a system of green spaces was developed to protect open space resources within the urban area. These policy developments resulted in measurable changes in the built environment characteristics since the early 1990s (Jun, 2008).

We sought to capitalize on the changes in the Portland region's physical environment. Using Metro's comprehensive regional spatial data and a large cohort study of older women residing in the Portland metropolitan region with longitudinal measures of body size and other health factors, we assessed whether change in the neighborhood environment is associated with change in adiposity, measured by BMI, in older women over an 18-year period.