Sally Liu

Prospective study of particulate air pollution exposures, subclinical atherosclerosis, and clinical cardiovascular disease: The Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air).

The Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) was initiated in 2004 to investigate the relation between individual-level estimates of long-term air pollution exposure and the progression of subclinical atherosclerosis and the incidence of cardiovascular disease (CVD). MESA Air builds on a multicenter, community-based US study of CVD, supplementing that study with additional participants, outcome measurements, and state-of-the-art air pollution exposure assessments of fine particulate matter, oxides of nitrogen, and black carbon. More than 7,000 participants aged 45-84 years are being followed for over 10 years for the identification and characterization of CVD events, including acute myocardial infarction and other coronary artery disease, stroke, peripheral artery disease, and congestive heart failure; cardiac procedures; and mortality. Subcohorts undergo baseline and follow-up measurements of coronary artery calcium using computed tomography and carotid artery intima-medial wall thickness using ultrasonography. This cohort provides vast exposure heterogeneity in ranges currently experienced and permitted in most developed nations, and the air monitoring and modeling methods employed will provide individual estimates of exposure that incorporate residence-specific infiltration characteristics and participant-specific time-activity patterns. The overarching study aim is to understand and reduce uncertainty in health effect estimation regarding long-term exposure to air pollution and CVD.

Association between short term exposure to fine particulate matter and heart rate variability in older subjects with and without heart disease

Background: Short term increases in exposure to particulate matter (PM) air pollution are associated with increased cardiovascular morbidity and mortality. The mechanism behind this effect is unclear, although changes in autonomic control have been observed. It was hypothesised that increases in fine PM measured at the subjects’ home in the preceding hour would be associated with decreased high frequency heart rate variability (HF-HRV) in individuals with pre-existing cardiac disease. Methods: Two hundred and eighty five daily 20 minute measures of HRV (including a paced breathing protocol) were made in the homes of 34 elderly individuals with (n = 21) and without (n = 13) cardiovascular disease (CVD) over a 10 day period in Seattle between February 2000 and March 2002. Fine PM was continuously measured by nephelometry at the individuals’ homes. Results: The median age of the study population was 77 years (range 57–87) and 44% were male. Models that adjusted for health status, relative humidity, temperature, mean heart rate, and medication use did not find a significant association between a 10 μg/m3 increase in 1 hour mean outdoor PM2.5 before the HRV measurement and a change in HF-HRV power in individuals with CVD (3% increase in median HF-HRV (95% CI −19 to 32)) or without CVD (5% decrease in median HF-HRV (95% CI −34 to 36)). Similarly, no association was evident using 4 hour and 24 hour mean outdoor PM2.5 exposures before the HRV measurement. Conclusion: No association was found between increased residence levels of fine PM and frequency domain measures of HRV in elderly individuals.

A community study of the effect of particulate matter on blood measures of inflammation and thrombosis in an elderly population.

BackgroundThe mechanism behind the triggering effect of fine particulate matter (PM) air pollution on cardiovascular events remains elusive. We postulated that elevated levels of PM would be associated with increased blood levels of inflammatory and thrombotic markers in elderly individuals. We also hypothesized that elevated PM would increase levels of cytokines in individuals with heart disease.MethodsWe measured these blood markers in 47 elderly individuals with (23) and without (16 COPD and 8 healthy) cardiovascular disease (CVD) on 2 or 3 mornings over a 5 or 10-day period between February 2000 and March 2002. Blood measures were paired with residence level outdoor PM measured by nephelometry. Analyses determined the within-individual effect of 24-hour averaged outdoor PM on blood measures.ResultsAnalyses found no statistically significant effect of a same day 10 ug/m3 increase in fine PM on log transformed levels of CRP 1.21 fold-rise [95% CI: 0.86, 1.70], fibrinogen 1.02 fold-rise [95% CI: 0.98, 1.06], or D-dimer 1.02 fold-rise [95% CI: 0.88, 1.17] in individuals with CVD. One-day lagged analyses in the CVD subgroup found similar null results. These same models found no change in these blood markers at the same-day or 1-day lag in the group without CVD. In 21 individuals with CVD, a 10 μg/m3 increase in same-day PM was associated with a 1.3 fold-rise [95% CI: 1.1, 1.7] in the level of monocyte chemoattractant protein-1.ConclusionWe did not find consistent effects of low ambient levels of PM on blood measures of inflammation or thrombosis in elderly individuals.

HMOX1 and GST variants modify attenuation of FEF25–75% decline due to PM10 reduction

Reduced exposure to particulate matter with a 50% cut-off aerodynamic diameter of 10 microm (PM(10)) attenuated age-related lung function decline in our cohort, particularly in the small airways. We hypothesised that polymorphisms in glutathione S-transferase (GST) and haem oxygenase-1 (HMOX1) genes, important for oxidative stress defence, modify these beneficial effects. A population-based sample of 4,365 adults was followed up after 11 yrs, including questionnaire, spirometry and DNA blood sampling. PM(10) exposure was estimated by dispersion modelling and temporal interpolation. The main effects on annual decline in forced expiratory flow at 25-75% of forced vital capacity (FEF(25-75%)) and interactions with PM(10) reduction were investigated for polymorphisms HMOX1 rs2071746 (T/A), rs735266 (T/A) and rs5995098 (G/C), HMOX1 (GT)(n) promoter repeat, GSTM1 and GSTT1 deletions, and GSTP1 p.Ile105Val, using mixed linear regression models. HMOX1 rs5995098, HMOX1 haplotype TTG and GSTP1 showed significant genetic main effects. Interactions with PM(10) reduction were detected: a 10 microg.m(-3) reduction significantly attenuated annual FEF(25-75%) decline by 15.3 mL.s(-1) only in the absence of HMOX1 haplotype ATC. Similarly, carriers of long (GT)(n) promoter repeat alleles or the GSTP1 Val/Val genotype profited significantly more from a 10 microg.m(-3) reduction (26.5 mL.s(-1) and 27.3 mL.s(-1) respectively) than non-carriers. Benefits of a reduction in PM(10) exposure are not equally distributed across the population but are modified by the individual genetic make-up determining oxidative stress defence.

Decreased PM10 exposure attenuates age-related lung function decline: genetic variants in p53, p21, and CCND1 modify this effect.

Background Decreasing exposure to airborne particulates was previously associated with reduced age-related decline in lung function. However, whether the benefit from improved air quality depends on genetic background is not known. Recent evidence points to the involvement of the genes p53 and p21 and of the cell cycle control gene cyclin D1 (CCND1) in the response of bronchial cells to air pollution. Objective We determined in 4,326 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) whether four single-nucleotide polymorphisms in three genes [CCND1 (rs9344 [P242P], rs667515), p53 (rs1042522 [R72P]), and p21 (rs1801270 [S31R])] modified the previously observed attenuation of the decline in the forced expiratory flow between 25% and 75% of the forced vital capacity (FEF25–75) associated with improved air quality. Methods Subjects of the prospective population-based SAPALDIA cohort were assessed in 1991 and 2002 by spirometry, questionnaires, and biological sample collection for genotyping. We assigned spatially resolved concentrations of particulate matter with aerodynamic diameter ≤ 10 μm (PM10) to each participant’s residential history 12 months before the baseline and follow-up assessments. Results The effect of diminishing PM10 exposure on FEF25–75 decline appeared to be modified by p53 R72P, CCND1 P242P, and CCND1 rs667515. For example, a 10-μg/m3 decline in aver-age PM10 exposure over an 11-year period attenuated the average annual decline in FEF25–75 by 21.33 mL/year (95% confidence interval, 10.57–32.08) among participants homozygous for the CCND1 (P242P) GG genotype, by 13.72 mL/year (5.38–22.06) among GA genotypes, and by 6.00 mL/year (−4.54 to 16.54) among AA genotypes. Conclusions Our results suggest that cell cycle control genes may modify the degree to which improved air quality may benefit respiratory function in adults.

Indoor- and Outdoor-Generated Particles: Koenig et al. Respond

We appreciate Moshammer’s comments and his interest in our research. We have several points to raise in reply.