In this study of cross-sectional data from Italy, researchers discovered a direct correlation between levels of particulate matter in the air and the increase in hospitalizations for diabetic patients over the age of 45.
This paper is part of our Environmental Medicine Special Issue. Read the entire issue below.
Reference
Solimini AG, D’Addario M, Villari P. Ecological correlation between diabetes hospitalizations and fine particulate matter in Italian provinces. BMC Public Health. 2015;15(1):708.
Design
Cross-sectional data were aggregated from Italian institutional and regional databases from 2008 through 2010 to determine correlations between hospital discharges with diabetes and fine particulate matter (PM2.5) levels, adjusting for common risk factors and socioeconomic factors.
Data
The data cover 48 Italian provinces, with a population of more than 34 million residents (60% of the total Italian population). The particulate matter up to 2.5 micrometers in size (PM2.5) average levels between 2008 and 2010 in the Italian provinces ranged between 11 μg/m3 to 32 μg/m3 with a mean of 20.1 μg/m3. Diabetes hospital discharge in patients older than 45 years ranged for women between 4.6 to 66.9 per 10,000 with a mean of 16.2; the range for men was between 8.4 and 83.8 per 10,000 with a mean of 23.4.
Particulate Measures
Annual levels of PM2.5 of Italian cities were obtained in hourly measurements from monitoring stations belonging to regional networks. The time period and the monitoring stations were chosen to match the hospital discharge data at the provincial level.
Key Findings
Diabetes hospitalizations increased with increased annual PM2.5 concentrations, with a rise of 3.5% (1.3%-5.6%) for men and of 4.0% (1.5%-6.4%) for women per μg/m3 of PM2.5 increase.
Practice Implications
This paper suggests that controlling exposure to air pollution may reduce incidence of diabetes and complications (in particular, hospitalizations) for diabetics. This is a connection that few practitioners think of when working with this patient population. While we are well aware that what and how much we eat impacts weight, metabolic syndrome, and diabetes, these 2 factors do not take into consideration how well we process calories. Increasing evidence shows that overexposure to environmental toxins from all sources can negatively affect human metabolic pathways.
Increasing evidence shows that overexposure to environmental toxins from all sources can negatively impact human metabolic pathways.
At least 5 cohort studies have sought an association between air pollution and type 2 diabetes. Krämer reported in 2010 that traffic-related air pollution was associated with incident type-2 diabetes among elderly women in the industrialized Ruhr region of Germany.1 A 2013 study that examined a cohort of more than 60,000 people in Ontario, Canada, reported an 11% increase in diabetes incidence per 10 μg/m3 increase in PM2.5.2
This study contrasts a report published in 2012 that, while finding a 25% increase in diabetes with interquartile increases in nitrogen dioxide (NO2) in a cohort of black women living in Los Angeles, did not find an association between diabetes and fine particulates.3 Two other US prospective cohorts also failed to find associations with diabetes and PM2.5 or PM10, yet they did find an association with “distance to road,” a stand-in marker for traffic-related pollution.4 In Denmark, Andersen et al found a borderline statistical association between confirmed cases of diabetes and NO2 levels.5 Pearson et al in 2010 reported a 1% increase in diabetes with an increase by 10 μg/m3 of PM2.5.6
This current Italian study suggests a greater risk increase than Pearson, a 35% increase for men and a 40% increase for women per 10 μg/m3 PM2.5. We should note that Pearson’s cohort was exposed to lower PM2.5 concentrations—2.5 μg/m3 to 17.7 μg/m3 (median=11 μg/m3)—compared to the people in this Italian study, whose exposure was 11 μg/m3 to 32 μg/m3 with a higher median=8.68 μg/m3.
Mechanisms exist to explain a possible association, in particular that the air pollutants increase systemic oxidative stress and trigger inflammatory changes that lead to insulin resistance.7,8 In animals, exposures to persistent organic pollutants are consistently associated with insulin resistance and type 2 diabetes.9 In addition, a review outlined how toxins can provoke insulin resistance through debilitated thyroid function and mitochondrial injury.10
Several studies now suggest that indoor air filtration systems, by reducing PM2.5 levels, also decrease markers of cardiovascular disease risk.11,12 Using the same manner of intervention, cleaning indoor air via filtration may potentially prove useful in treating insulin resistance, lowering incident diabetes, and reducing risk of diabetic complications and hospitalizations.
