A new study has revealed that short-term and long-term exposure to fine-particle air pollution may lead to an increase in hospitalizations among older adults.
The Harvard study, conducted by Joel D. Schwartz, PhD, and colleagues, revealed for each 10 µg/m3 (micrograms per cubic meter of air) increase in short-term exposure to fine airborne particulate matter, there was observed to be a 0.70% increase in hospital admissions for respiratory illnesses among patients 65 and older.
For long-term exposure for each 10 µg/m3, the increase was a bit more dramatic with a 4.22% increase in respiratory hospitalizations, according to the study reported online in PLoS One.
It has long been known that short-term exposure to air pollution has been linked to spikes in hospitalization among the elderly. The causes for these hospitalizations range from pneumonia to cardiovascular disease and diabetes.
Less was known about the link between long-term exposure and hospitalizations. To investigate the effects of chronic exposure to particulate matter ≤2.5 microns in aerodynamic diameter (PM2.5) over large areas, Schwartz and his colleagues developed a method in which they used satellite measurements of aerosol optical depth across the entire area of New England.
The daily aerosol data was then combined with measurements of PM2.5 measured on the ground at multiple monitoring sites and was adjusted for variables like wind, temperature, road traffic and open space.
This data was then used for prediction models for short- and long-term PM2.5 concentrations across individual 10×10 km grids. Long-term exposure was defined as the average exposure in each Zip code for the entire 7-year duration of the study. Short-term exposure was defines as the difference between the 2-day average exposure and the long-term average exposure.
The Harvard researchers then examined Medicare admissions in 3,000 area hospitals, from 2000 to 2008, for diagnoses of all respiratory causes, cardiovascular disease, stroke and diabetes.
Researchers found for areas with high levels of pollution, women were more commonly hospitalized. Women accounted for 56% of admissions for respiratory conditions, 55% of admissions for cardiovascular disease, 59% for strokes and 57% for diabetes.
Researchers also found for each 10 µg/m3 increase in PM2.5 exposure there was a 1.03% increase in hospital admissions for cardiovascular disease, a 0.24% increase in admissions for strokes and a 0.96 increase in diabetes.
For long-term exposure, larger increases were seen. There was a 3.12% in admissions for cardiovascular disease, 3.49% increase in admissions for stroke and a 6.33% increase admissions for diabetes.
The authors of the study suggested that numerous potential mechanisms could contribute to health problems in the elderly. These included direct effects on tissues of the lung and heart, and indirect effects through inflammation and oxidative stress.
The authors noted that a recent study suggest that mice prone to atherosclerosis developed worse and more unstable plaque when exposed to airborne particulate matter.
There were limitations to the study. These limitations included lack of data on individual patients, such as diet and exercise or socioeconomic status. There was also a limitation in spatial resolution being used.
“However, as satellite remote sensing evolves and progresses, higher spatial resolution data (3×3 km and 1×1 km) should become available which will further reduce exposure error,” wrote Schwartz and colleagues.
“These findings present new opportunities to study the effects of both the long and short term exposure and human health,” they concluded.