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Objective:
There is increasing evidence that air pollution may have an impact on observed regional variations in disease incidence and hospital admissions. A recent national study demonstrated that the number of hospital admissions for cardiac and respiratory diseases was associated with daily fluctuations in airborne fine particulate matter concentrations < 2.5 µm (PM_2.5). This study examines the previously unreported relationship between regional variations in hospital admissions for Peripheral Arterial Disease (PAD) and regional estimates of PM_2.5 concentrations.
Methods:
The Center for Medicare and Medicaid Services Limited Data Set for 2008 was used to identify all U.S. hospital admissions for PAD among patients insured by Medicare. Annual mean PM_2.5 concentration estimates were calculated for each county in the United States based on 2008 data from the Environmental Protection Agency. Pearson correlations and multiple regression analyses were used to examine the association between county level PM_2.5 estimates and the county level incidence of PAD admissions and associated surgical procedures (above and below knee amputations).
Results:
There were 847668 admissions for PAD, 14407 below knee amputations, and 13466 above knee amputations. The annual mean PM_2.5 level per county was (Mean + SD) 9.88 + 2.04; range: 4.27 - 16.39 across the 3096 counties for which data were available. Statistically significant direct correlations (p < 0.001) were observed between PM_2.5 levels and the percentage of Medicare admissions for PAD per county (r = 0.21), and those undergoing above knee amputation (r = 0.12). Statistically significant inverse correlations were observed between PM_2.5 levels and age of PAD patients (r = -0.22), and with male gender of PAD patients (r = -0.11). Multiple regression analyses revealed that the relationship between county annual percentage of Medicare PAD admissions and PM_2.5 was independent of the size of the county populations.
Conclusions:
This study suggests that Medicare patients may have a higher likelihood of hospital admission for PAD if they live in an area with higher levels of airborne fine particulate matter concentrations. Further, the data suggest that patients admitted for PAD who reside in more highly polluted regions tend to be younger and are more likely to be female than those living in less polluted regions. If confirmed in future studies, these results may have significant implications for public health and resource allocation.