Residential mobility impacts exposure assessment and community socioeconomic characteristics in longitudinal epidemiology studies

Abstract

Epidemiologic studies commonly use residential locations to estimate environmental exposures or community-level characteristics. The impact of residential mobility on these characteristics, however, is rarely considered. The objective of this analysis was to examine the effect of residential mobility on estimates of traffic-related air pollution (TRAP), greenspace, and community-level characteristics. All residential addresses were reported from birth through age seven for children enrolled in the Cincinnati Childhood Allergy and Air Pollution Study. Exposure to TRAP at each address was estimated using a land use model. Greenspace was estimated using satellite imagery. Indices of neighborhood deprivation and race were created based on socioeconomic-census tract measures. Exposure estimates using the birth record address, the last known address, and the annual address history were used to determine exposure estimation error and bias in the association with asthma at age seven. Overall, 54% of the cohort moved at least once prior to age seven. Each move was separated by a median of 4 miles and associated with a median decrease of 4.4% in TRAP exposure, a 5.3% increase in greenspace, an improved deprivation index, and no change in the race index. Using the birth record address or the last known address instead of the annual address history resulted in exposure misclassification leading to a bias toward the null when associating the exposures with asthma. Using a single address to estimate environmental exposures and community-level characteristics over a time period may result in differential assessment error.

Figure 1

Quantifying residential changes: (a) Total number of times that each child moved, (b) Child's age at each move, (c) Histogram of the change in distance for each move (each bar represents a 1 mile interval).

Figure 2

Changes in exposure measurements due to all moves: (a) Percent change by each move number and all moves combined, (b) old versus new values for all moves. The blue line and shaded region is a locally fit polynomial regression line with an associated 95% confidence interval and the dotted line is the line of equality between new and old values.

Figure 3

Differences in exposure estimation according to address selection method: (a) mean versus birth (b) mean versus last.

Figure 4

Hazard ratio predictions from the cox proportional hazards model. Hazard ratios are presented as compared to a subject with mean covariate values (TRAP: 0.38 μg/m³, Deprivation index: 0.41, greenspace: 0.54). Each panel represents differing quantiles of TRAP concentrations (10%: 0.27, 25%: 0.29, 50%: 0.34, 75%: 0.42, 90%: 0.57). Each hazard ratio is based on the mean value of greenspace (0.54).