Annual ambient black carbon associated with shorter telomeres in elderly men: Veterans Affairs Normative Aging Study

Abstract

Background: Telomere length reflects biological age and is inversely associated with risk of cardiovascular disease (CVD). Ambient air pollution is associated with CVD, but its effect on telomere length is unknown.

Objective: We investigated whether ambient black carbon (BC), a marker for traffic-related particles, is associated with telomere length in the Normative Aging Study (NAS).

Methods: Among 165 never-smoking men from the NAS, leukocyte telomere length (LTL) was measured repeatedly approximately every 3 years from 1999 through 2006 using quantitative real-time polymerase chain reaction (qRT-PCR). BC concentration at their residences during the year before each LTL measurement was estimated based on a spatiotemporal model calibrated with BC measurements from 82 locations within the study area.

Results: The median [interquartile range (IQR)] annual moving-average BC concentration was 0.32 (0.20-0.45) microg/m3. LTL, expressed as population-standardized ratio of telomere repeat to single-copy gene copy numbers, had a geometric mean (geometric SD) of 1.25 (1.42). We used linear mixed-effects models including random subject intercepts and adjusted for several potential confounders. We used inverse probability of response weighting to adjust for potential selection bias due to loss to follow-up. An IQR increase in annual BC (0.25 microg/m3) was associated with a 7.6% decrease (95% confidence interval, -12.8 to -2.1) in LTL. We found evidence of effect modification, with a stronger association among subjects > or = 75 years of age compared with younger participants (p = 0.050) and statin medications appearing protective of the effects of BC on LTL (p = 0.050).

Conclusions: Telomere attrition, linked to biological aging, may be associated with long-term exposures to airborne particles, particularly those rich in BC, which are primarily related to automobile traffic.

Figure 1

Maps of study area in eastern Massachusetts showing (A) locations of BC monitors used in spatiotemporal statistical model and (B) approximate locations of residences of NAS participants, with coding (white, gray, black) to indicate quintiles of annual moving averages of predicted daily BC concentrations, 1999–2006.

Figure 2

Modification of the effect of annual moving-average BC concentration on LTL by age and statin treatment: NAS, 1999–2006. Estimated percent differences (95% CIs) associated with an interquartile increase (0.25 μg/m³) in annual BC are shown, adjusted for baseline age; change in age between measures; year; BMI (quadratic); white blood cell count; percent neutrophils; percent lymphocytes; treatment with statin medication (yes, no); diagnosis of diabetes (yes, no); fasting blood glucose; education level (< high school, high school graduate, < 4 years of college, 4 years of college, > 4 years of college); National Atlas of the United States urban indicator for residence location, census-tract–level median income, and percentage of population below poverty line; and potential selection bias due to loss to follow-up by inverse probability of follow-up response weighting.