Changes in walking, body mass index, and cardiometabolic risk factors following residential relocation: Longitudinal results from the CARDIA study

Abstract

Background While many studies have found the built environment to be associated with walking, most have used cross-sectional research designs and few have examined more distal cardiometabolic outcomes. This study contributes longitudinal evidence based on changes in walking, body mass index (BMI), and cardiometabolic risk following residential relocation. Methods We examined 1,079 participants in the CARDIA study who moved residential locations between 2000 and 2006 (ages 32–46 in 2000, 49% white/51% black, 55% female). We created a walkability index from measures of population density, street connectivity, and food and physical activity resources, measured at participants’ pre- and post-move residential locations. Outcomes measured before and after the move included walking, BMI, waist circumference, blood pressure, insulin resistance, triglycerides, cholesterol, atherogenic dyslipidemia, and C-reactive protein. Fixed effects (FE) models were used to estimate associations between within-person change in walkability and within-person change in each outcome. These estimates were compared to those from random effects (RE) models to assess the implications of unmeasured confounding. Results In FE models, a one-SD increase in walkability was associated with a 0.81 mmHg decrease in systolic blood pressure [95% CI: (−1.55, −0.07)] and a 7.36 percent increase in C-reactive protein [95% CI: (0.60, 14.57)]. Although several significant associations were observed in the RE models, Hausman tests suggested that these estimates were biased for most outcomes. RE estimates were most commonly biased away from the null or in the opposite direction of effect as the FE estimates. Conclusions Greater walkability was associated with lower blood pressure and higher C-reactive protein in FE models, potentially reflecting competing health risks and benefits in dense, walkable environments. RE models tended to overstate or otherwise misrepresent the relationship between walkability and health. Approaches that base estimates on variation between individuals may be subject to bias from unmeasured confounding, such as residential self-selection.

Moving to an active lifestyle? A systematic review of the effects of residential relocation on walking, physical activity and travel behaviour

“…Alternatively, if the authors explicitly discussed that one model is less biased than the other, we then coded this association based on the less biased model. For example, Braun et al tested the association between a walkability index and walking outcomes using both random and fixed effects models 27. They argued that estimates from random effects models were more biased because of residual self-selection bias; we therefore coded this association based on results from the fixed effects model.…”

“…Neither do they have control over the dose of the intervention. As environmental change is usually slow and incremental,27 it may not provide a sufficient ‘dose’ required for behavioural change during the time frame of the evaluation. In fact, some evaluations of environmental interventions on physical activity had mixed findings14 possibly due to these challenges.…”

Communicating the benefits of population health interventions: The health effects can be on par with those of medication

“… 3.2 Antihypertensive medications: The effect of one standard dose of antihypertensive medications is estimated between 5.7 mmHg to 11.7 mmHg and 3.1 mmHg to 6.9 mmHg in reduced systolic and diastolic blood pressure, depending upon pre-treatment level ( Law et al, 2009 ). Increasing neighbourhood walkability: A cohort study showed 1-standard deviation (7.95 unit) increase in neighbourhood walkability was associated with a 0.81 mmHg reduction (95%CI -1.55 to -0.07) in systolic blood pressure ( Braun et al, 2016 ). Increasing neighbourhood walkability could reduce systolic blood pressure by a little under 1 mmHg, compared with a 5.7–11.7 mmHg reduction from a standard dose of antihypertensive medication (depending upon pre-treatment levels).…”

“… Chiu et al, 2016 ), with the effect partially mediated by change in body weight ( Chaix et al, 2008 ). A recent US-based cohort study ( Braun et al, 2016 ) tracked change in blood pressure over 6 years among people moving from neighbourhoods of low to high walkability. ‘Fixed effect’ models adjusted for time-varying sources of confounding found a 1-standard deviation increase in local walkability to be associated with a 0.81 mmHg reduction (95%CI -1.55 to -0.07) in systolic blood pressure.…”

“…International Journal of Environmental Health Research, 15, 319–337. United Kingdom 100 Mean age at baseline = 25 55% Approximately 25 min (5 min after completing 20 min of exercise) One-way ANOVA Increasing neighbourhood walkability Braun et al (2016) . Changes in walking, body mass index, and cardiometabolic risk factors following residential relocation: Longitudinal results from the CARDIA study.…”