Air Pollution and Performance-Based Physical Functioning in Dutch Older Adults

Background: Functional limitations are a major cause for needing care and institutionalization among older adults. Exposure to air pollution has been suggested to be associated with increased functional limitations in older people. Objective: Our objective was to assess the association between air pollution and physical functioning in Dutch older adults. Methods: We analyzed data on performance-based (walking speed, ability to rise from a chair, putting on and taking off a cardigan, balance test) and self-reported physical functioning for 1,762 participants of the Longitudinal Aging Study Amsterdam, who participated in measurement cycles performed in 2005/2006, 2008/2009, and 2011/2012. Annual average outdoor air pollution concentrations [nitrogen dioxide (NO2), nitrogen oxides (NOx), particulate matter with diameters ≤2.5μm (PM2.5), ≤10μm (PM10), and 2.5–10μm (PMcoarse), and PM2.5 absorbance] at the home address at the start of the first measurement cycle were estimated using land-use regression models. Analyses were performed using mixed models with random participant intercepts adjusting for potential confounders. Results: Exposure to most air pollutants was associated with reduced performance-based physical functioning; for example, an interquartile range increase in NO2 exposure was associated with a 0.22 (95% confidence interval: 0.03, 0.42) lower performance test score in fully adjusted models, equivalent to the difference in performance score between participants who differed by 9 mo in age. Exposure to air pollution was generally not statistically significantly associated with self-reported functional limitations, and not associated with a faster decline in performance-based physical functioning over the study period. Conclusion: This study suggests that exposure to air pollution may adversely affect physical performance of older adults in the Netherlands. https://doi.org/10.1289/EHP2239

. Land-use regression models with model performance (leave-one-out cross-validation R 2 , R 2 LOOCV ). Table S2. Distribution of baseline performance scores by participant characteristics (N=1,762 participants). Table S3. Residential exposure to air pollution -Pearson correlations between pollutants. Table S4. Distribution of daily average air pollution concentrations on the days of the physical performance test for all study participants. Table S5. Adjusted associations between performance-based physical functioning and residential air pollution exposure from linear mixed model analyses with additional adjustment for air pollution concentrations during the week preceding the performance test. Table S6. Adjusted associations between physical performance (performance-based and selfreported) and residential air pollution exposure from linear mixed model analyses, restricted to participants who completed all three cycles of data collection. Table S7. Adjusted associations between physical performance (performance-based and self-reported) and residential air pollution exposure from linear mixed model analyses, restricted to participants who did not change address between three years prior to the 2005/2006 cycle and the last completed cycle. Table S8. Post hoc sensitivity analyses of residual confounding of the association between air pollution and performance-based physical functioning due to an unmeasured binary confounder (U). Table S9. Adjusted associations between physical performance (performance-based and selfreported) and residential air pollution exposure from linear mixed model analyses without exposure-time since baseline interaction terms. Figure S1. Flow-chart of the study sample. Figure S2. Adjusted associations between self-reported physical functioning and quartiles of residential air pollution exposure from linear mixed model analyses with p-values of F-tests for equality of means and trend tests using quartile midpoints (N=1,758 participants, n=4,405 observations).

Figure S3
. Adjusted sex-specific associations between performance-based physical functioning and residential air pollution exposure from linear mixed model analyses with exposure-sex interaction terms (N=1,735 participants, n=4,039 observations). Grey dots represent females, white dots represent males. DISTINVMAJOR1: inverse distance (m -1 ) to the nearest road of the local road network; DISTINVNEARC1: Inverse distance to the nearest road; HEAVYTRAFLOAD_X: Total heavy-duty traffic load of all roads in X m buffer (sum of (heavy-duty traffic intensity *length of all segments)); HLDRES_X: Sum of high density and low density residential land in X m buffer; MAJORROADLENGTH_X: Road length of major roads in X m buffer; POP_X: Number of inhabitants in X m buffer; PORT: port in X m buffer; REGIONALESTIMATE: Regional estimate; ROADLENGTH_X: Road length of major roads in X m buffer; TRAFLOAD_X: Total traffic load of all roads in X m buffer (sum of (traffic intensity * length of all segments)); TRAFMAJORLOAD_X: Total traffic load of major roads in X m buffer (sum of (traffic intensity * length of all segments)); TRAFNEAR: Traffic intensity on nearest road; Associations are presented as mean difference in physical performance score with 95% confidence intervals (CI) for an interquartile range increase in air pollution exposure and were derived from models with exposure and exposure-time since baseline interaction. c N=1,247 participants, n = 3,042 observations d N=1,287 participants, n = 3,218 observations Supplemental material, Table 8. Post hoc sensitivity analyses of residual confounding of the association between air pollution and performance-based physical functioning due to an unmeasured binary confounder (U).

Outcome
Performance-based physical functioning Exposure contrast 4th vs 1st quartile of NO 2 exposure Effect estimate (exposure -outcome) -0.46 points Difference in outcome per year -0.30 points Prevalence differences are absolute not relative differences. Given the difference in U prevalence shown, the minimum OR of high exposure is the smallest OR across all possible pairs of U prevalence.

Hypothetical relation of U to cognitive outcome (U -outcome)
Supplemental material, Table S9. Adjusted a associations b between physical performance (performance-based and self-reported) and residential air pollution exposure from linear mixed model analyses without exposure-time since baseline interaction terms.
Performance-based c Self-reported d Associations are presented as mean difference in physical performance score with 95% confidence intervals (CI) for an interquartile range increase in air pollution exposure.
Supplemental material, Figure S1. Flow-chart of the study sample. Supplemental material, Figure S2. Adjusted a associations b between self-reported physical functioning and quartiles of residential air pollution exposure from linear mixed model analyses with p-values of F-tests for equality of means and trend tests using quartile midpoints (N=1,758 participants, n=4,405 observations). Associations are presented as mean difference in physical performance score in the different quartiles as compared to the 1 st quartile with 95% confidence intervals and were derived from models with exposure and exposure-time since baseline interaction.
Supplemental material, Figure S3. Adjusted a sex-specific associations b between performancebased physical functioning and residential air pollution exposure from linear mixed model analyses with exposure-sex interaction terms (N=1,735 participants, n=4,039 observations).
Grey dots represent females, white dots represent males. Associations are presented as mean difference in physical performance score with 95% confidence intervals (CI) for an interquartile range increase in air pollution exposure and were derived from models with exposure and exposure-time since baseline interaction.