p53, CCND1, and p21 variants modify PM10 effect age-related FEF25–75 decline was attenuated by reduced exposure to PM with aerodynamic diameter ≤ 10 µm (PM10). Materials and Methods SAPALDIA cohort study population. The study design and methodology of SAPALDIA have been described in detail elsewhere (Ackermann-Liebrich et al. 2005; Martin et al. 1997). In 1991, health examinations focusing on respiratory health status were conducted in 9,651 adults (18–60 years of age) randomly selected from population regis- tries of eight environmentally diverse areas of Switzerland. Ethical approval was obtained from the Swiss Academy of Medical Sciences and the Regional Ethics Committees. Written informed consent was obtained from all participants before health examination and biological sample collection at both surveys. Nonparticipation at follow-up and missing information on covariates led to the exclu- sion of participants for the present study [see Supplemental Material, Figure 1 and Table 2 available online (doi:10.1289/ehp.0800430. S1 via http://dx.doi.org)]. In summary, of the 9,651 subjects who initially participated at baseline (SAPALDIA1), 1,604 had died, left Switzerland, or refused to participate at the follow-up examination (SAPALDIA2). Of 8,047 cohort participants remaining, 5,732 completed the interview questionnaire and spirometry at both the baseline and fol- low-up surveys. Participants were excluded from the analysis (n = 1,406) if they had lived for < 1 year at their last residential address at follow-up, could not be assigned home out- door PM10 concentrations, or did not provide blood samples for DNA extraction or if the genetic analysis of their sample was unsuccess- ful. Thus, the present study sample included 4,326 participants with available blood sam- ples and genotype data and complete data from both surveys on spirometry, smoking history, PM10 exposure, and residential history during follow-up. Lung function assessment. Identical spirometer devices (model 2200, SensorMedics Corp., Yorba Linda, CA, USA) and protocols were used at baseline and follow-up examina- tions, and their comparability was assessed before the follow-up study (Künzli et al. 1995, 2005). Details of these measurements have been described elsewhere (Ackermann-Liebrich et al. 2005; Downs et al. 2005). Briefly, three to eight forced expiratory lung function maneuvers were performed by each partici- pant to obtain a minimum of two measures of FEF, FVC, forced expiratory volume in the first second (FEV1), and FEF25–75 that were considered acceptable according to American Thoracic Society (1995) criteria. Expiratory flow measures were taken from the same flow- volume curve. For each participant, the rate of change in lung function was defined as the difference in each parameter between the two examinations (measurement at follow-up minus measurement at baseline), divided by the participant-specific follow-up time (in nontruncated years). Selection of genetic variants. We selected the same common, well-studied, and poten- tially functional candidate single-nucleotide polymorphism (SNP) in CCND1 [proline- to-proline substitution at amino acid 242 (P242P), rs9344] that we evaluated in our pre- vious research on the interaction of CCND1 with oxidative stress in breast and colon can- cer (Ceschi et al. 2005; Probst-Hensch et al. 2006). We selected one additional common SNP in the CCND1 gene (rs667515) based on a pilot study involving haplotype-tagging poly- morphisms in CCND1 and their association with accelerated lung function decline in a subsample of the SAPALDIA cohort (unpub- lished observations). In addition, we examined SNPs in two other important cell cycle control genes that have been repeatedly assessed in cancer association studies and are reported to have a functional effect: p53 [arginine-to- proline substitution at amino acid 72 (R72P), rs1042522] (Bergamaschi et al. 2006) and p21 [serine-to-arginine substitution at amino acid 31 (S31R), rs1801270](Lukas et al. 1997). Genotpying. DNA was extracted from EDTA-buffered whole blood as previously described (Ackermann-Liebrich et al. 2005). Genotyping strategy used was fluorescent 5´-nuclease real-time polymerase chain reac- tion (TaqMan, Applera Europe, Rotkreuz, Switzerland) methodology using ABI Prism 7900 sequence detection system (ABI, Rotkreuz, Switzerland). The SNP-specific primers and locked nucleic acid (LNA) dual- labeled fluorogenic probes were designed by Sigma Proligo (Evry, France). SNP-specific probes and primers were as follows: rs1042522, 5´-CTGCTCCCC[C/G]CGTGGC-3´, for- ward 5´-ACTGAAGACCCAGGTCCA-3´, reverse 5´-GCCGGTGTAGGAGCT-3´; rs1801270, 5´-GCTGAG[C/A]CGCGAC-3´, forward 5´-TGCCGCCGCCTCTT-3´, reverse 5´-GATGCAGCCCGCCATTAG-3´; rs667515, 5´-AGCTCCCTTGC[G/C] C C C - 3 ´ , f o r w a r d 5 ´ - T G G C T T C A T ­ C A G A T G A C A A C - 3 ´ , r e v e r s e 5´-AACCTGGGCTTCTCCAA-3´; rs9344, 5´-TGTGACCC[A/G]GTAAGTGA-3´, for- ward 5´-ACGCTTCCTCTCCAGAG­ 3´, reverse 5´-CAAGGCTGCCTGG-3´. A 10% random sample of all DNA samples was regenotyped, and all genotypes were con- firmed. The genotype call rate was > 99%. Individual residential PM10 exposure assessment. Air pollution exposure assessment has been described in detail elsewhere (Downs et al. 2007; Liu et al. 2007). We estimated PM10 exposure for each participant according Environmental Health Perspectives • volume 117 | number 9 | September 2009 to residential history using a hybrid exposure model incorporating Gaussian dispersion (from PolluMap model, version 2.0; Liu et al. 2007) and geoinformation based on data on seasonal, meteorologic, and geographic annual emission characteristics from various source categories (e.g., traffic, industrial, regional, and agricultural activities) (Liu et al. 2007). Hourly concentrations of PM10 were simulated with a spatial resolution of 200 × 200 m grid cells for 1990 and 2002. Annual average PM10 expo- sure concentrations during follow-up were esti- mated for each residential address with the help of an algorithm that allowed interpolation of modeled values on the basis of historical trends in central-site measurements between 1990 and 2002. Evaluation of dispersion model pre- dictions using a total of 57 PM10 Swiss central- site monitors has been described elsewhere (Liu et al. 2007). Based on the validated dispersion model, each subject was assigned an annual PM10 concentration every year between 1990 and 2002. For that purpose, modeled PM10 concentrations were averaged over the year to obtain annual averages for each grid cell. Each participant’s residential history was coded using the geographic information system data. Assignment of individual PM10 exposure was performed by matching address codes with annual concentrations derived from the grid cells generated by the dispersion model. The exposure variable used for the pres- ent study was the difference in the annual average PM10 exposure between 2002 and 1991. It was calculated for each participant as follows: average home outdoor PM10 con- centration in the 12 months before the base- line examination was subtracted from the corresponding average concentration in the 12 months before the follow-up examination, and this difference was divided by the mean time of follow-up (in nontruncated years). In our previous study (Downs et al. 2007), we used two exposure indexes: a) the differ- ence in the annual average exposure between 2002 and 1991 (the index used in the present study ) and b) the “interval exposure,” defined as the sum of the annual exposures for each subject for each year of follow-up between their examinations. Because of the high cor- relation (R2 > 0.9) between these two expo- sure variables, we were unable to single out the superior measure in our previous report. Both indices showed similar associations with change in lung function (Downs et al. 2007). C o l l e c t i o n o f d a t a o n c o v a r i a t e s . Information on relevant covariates known or likely to determine lung function decline, such as age, height, smoking history, ETS expo- sure, occupational exposure, and education level, was gathered in a computer-assisted, individually administered interview based on the European Community Respiratory Health Survey questionnaire (Burney et al. 1994). 1421