Biomedical subjects

J Schwartz

Publications and source records attributed to J Schwartz.

At least 19 recordsLinked to original sources

PubMed2006

Air pollution and inflammation in type 2 diabetes: a mechanism for susceptibility.

BACKGROUND: Particulate air pollution has been associated with several adverse cardiovascular health outcomes, and people with diabetes may be especially vulnerable. One potential pathway is inflammation and endothelial dysfunction-processes in which cell adhesion molecules and inflammatory markers play important roles. AIM: To examine whether plasma levels of soluble intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and von Willebrand factor (vWF) were associated with particle exposure in 92 Boston area residents with type 2 diabetes. METHODS: Daily average ambient levels of air pollution (fine particles (PM2.5), black carbon (BC) and sulphates) were measured approximately 500 m from the patient examination site and evaluated for associations with ICAM-1, VCAM-1 and vWF. Linear regressions were fit to plasma levels of ICAM-1, VCAM-1 and vWF, with the particulate pollutant index, apparent temperature, season, age, race, sex, glycosylated haemoglobin, cholesterol, smoking history and body mass index as predictors. RESULTS: Air pollutant exposure measures showed consistently positive point estimates of association with the inflammatory markers. Among participants not taking statins and those with a history of smoking, associations between PM(2.5), BC and VCAM-1 were particularly strong. CONCLUSIONS: These results corroborate evidence suggesting that inflammatory mechanisms may explain the increased risk of air pollution-associated cardiovascular events among those with diabetes.

Adult↗

PubMed2006

Effects of exposure to air pollution on blood coagulation.

BACKGROUND: Consistent evidence has indicated that air pollution increases the risk of cardiovascular diseases. The underlying mechanisms linking air pollutants to increased cardiovascular risk are unclear. OBJECTIVES: We investigated the association between the pollution levels and changes in such global coagulation tests as the prothrombin time (PT) and the activated partial thromboplastin time (APTT) in 1218 normal subjects from the Lombardia Region, Italy. Plasma fibrinogen and naturally occurring anticoagulant proteins were also evaluated. METHODS: Hourly concentrations of particulate (PM10) and gaseous pollutants (CO, NO2, SO2, and O3) were obtained from 53 monitoring sites covering the study area. Generalized additive models were applied to compute standardized regression coefficients controlled for age, gender, body mass index, smoking, alcohol, hormone use, temperature, day of the year, and long-term trends. RESULTS: The PT became shorter with higher ambient air concentrations at the time of the study of PM10 (coefficient = -0.06; P < 0.05), CO (coefficient = -0.11; P < 0.001) and NO2 (coefficient =-0.06; P < 0.05). In the 30 days before blood sampling, the PT was also negatively associated with the average PM(10) (coefficient = -0.08; P < 0.05) and NO2 (coefficient = -0.08; P < 0.05). No association was found between the APTT and air pollutant levels. In addition, no consistent relations with air pollution were found for fibrinogen, antithrombin, protein C and protein S. CONCLUSIONS: This investigation shows that air pollution is associated with changes in the global coagulation function, suggesting a tendency towards hypercoagulability after short-term exposure to air pollution. Whether these changes contribute to trigger cardiovascular events remains to be established.

Adolescent↗

PubMed2006

Allogeneic stem cell transplantation corrects biochemical derangements in MNGIE.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a multisystemic autosomal recessive disease due to primary thymidine phosphorylase (TP) deficiency. To restore TP activity, we performed reduced intensity allogeneic stem cell transplantations (alloSCTs) in two patients. In the first, alloSCT failed to engraft, but the second achieved mixed donor chimerism, which partially restored buffy coat TP activity and lowered plasma nucleosides. Thus, alloSCT can correct biochemical abnormalities in the blood of patients with MNGIE, but clinical efficacy remains unproven.

Adult↗

PubMed2006

Ambient particulate air pollution and cardiac arrhythmia in a panel of older adults in Steubenville, Ohio.

OBJECTIVES: Ambient particulate air pollution has been associated with increased risk of cardiovascular morbidity and mortality. Pathways by which particles may act involve autonomic nervous system dysfunction or inflammation, which can affect cardiac rate and rhythm. The importance of these pathways may vary by particle component or source. In an eastern US location with significant regional pollution, the authors examined the association of air pollution and odds of cardiac arrhythmia in older adults. METHODS: Thirty two non-smoking older adults were evaluated on a weekly basis for 24 weeks during the summer and autumn of 2000 with a standardised 30 minute protocol that included continuous electrocardiogram measurements. A central ambient monitoring station provided daily concentrations of fine particles (PM(2.5), sulfate, elemental carbon) and gases. Sulfate was used as a marker of regional pollution. The authors used logistic mixed effects regression to examine the odds of having any supraventricular ectopy (SVE) or ventricular ectopy (VE) in association with increases in air pollution for moving average pollutant concentrations up to 10 days before the health assessment. RESULTS: Participant specific mean counts of arrhythmia over the protocol varied between 0.1-363 for SVE and 0-350 for VE. The authors observed odds ratios for having SVE over the length of the protocol of 1.42 (95% CI 0.99 to 2.04), 1.70 (95% CI 1.12 to 2.57), and 1.78 (95% CI 0.95 to 3.35) for 10.0 microg/m3, 4.2 microg/m3, and 14.9 ppb increases in five day moving average PM2.5, sulfate, and ozone concentrations respectively. The other pollutants, including elemental carbon, showed no effect on arrhythmia. Participants reporting cardiovascular conditions (for example, previous myocardial infarction or hypertension) were the most susceptible to pollution induced SVE. The authors found no association of pollution with VE. CONCLUSION: Increased levels of ambient sulfate and ozone may increase the risk of supraventricular arrhythmia in the elderly.

Aged↗

PubMed2006

Delta-aminolevulinic acid dehydratase polymorphism and the relation between low level lead exposure and the Mini-Mental Status Examination in older men: the Normative Aging Study.

OBJECTIVE: To determine whether a polymorphism the in delta-aminolevulinic acid dehydratase (ALAD) gene modifies the neurotoxicity of lead in older adults. METHODS: The authors studied men participating in the Department of Veterans Affairs' Normative Aging Study, assessing their recent exposure to lead by measuring blood lead (n = 915) at each triennial clinic visit, and, beginning in 1991, assessing their cumulative exposure by measuring lead levels in tibia (n = 722) and patella (n = 720), using K-shell x ray fluorescence. Starting in 1993 and again at each triennial visit, the authors administered the Mini-Mental State Examination (MMSE) to assess their cognitive functioning. The relation of the lead biomarkers to MMSE score was evaluated and this association was compared among men who carried the variant allele, ALAD-2, versus men without the allele. RESULTS: Sixteen per cent of men carried the ALAD-2 allele. Median tibia and patella lead levels (first-third quartile) were 19 (13-28) and 27 (18-39) microg/g. Blood lead levels were consistent with non-occupational exposure: only 6% of men had levels > or =10 microg/dl. In multivariable adjusted analyses, higher levels of blood lead were associated with poorer performance on the MMSE. This association was most pronounced among ALAD-2 carriers, among whom a 3 microg/dl increment in blood lead (the interquartile range) was associated with a 0.26 point lower mean MMSE score (95% CI -0.54 to 0.01), compared with a 0.04 point lower score (95% CI -0.16 to 0.07) among non-carriers. The modest 0.22 point difference in these associations did not attain statistical significance, however (p(interaction) = 0.13). The associations between bone lead levels and MMSE score did not vary by ALAD-2 status. CONCLUSIONS: Although not statistically significant, these findings suggest that ALAD genotype may modify blood lead's adverse association with cognition among older men who had community exposures to lead. However, despite a relatively large sample size and the use of sensitive methods for measuring lead burden, the evidence overall was fairly weak.

Adult↗

PubMed2006

Association of ventricular arrhythmias detected by implantable cardioverter defibrillator and ambient air pollutants in the St Louis, Missouri metropolitan area.

BACKGROUND: It has previously been reported that the risk of ventricular arrhythmias is positively associated with ambient air pollution among patients with implantable cardioverter defibrillators (ICD) in Boston. AIMS: To assess the association of community exposures to air pollution with ventricular arrhythmias in a cohort of ICD patients in metropolitan St Louis, Missouri. METHODS: ICD detected episodes reported during clinical follow up were abstracted and reviewed by an electrophysiologist to identify ventricular arrhythmias. A total of 139 ventricular arrhythmias were identified among 56 patients. A case-crossover design was used with control periods matched on weekday and hour of the day within the same calendar month. Conditional logistic regression models were adjusted for temperature, barometric pressure, and relative humidity in the 24 hours preceding the event. RESULTS: There was a significant (24%, 95% CI 7% to 44%) increase in risk of ventricular arrhythmias associated with each 5 ppb increase in mean sulphur dioxide and non-significantly increased risk (22%, 95% CI -6% to 60%; and 18%, 95% CI -7% to 50%) associated with increases in nitrogen dioxide (6 ppb) and elemental carbon (0.5 microg/m3), respectively in the 24 hours before the arrhythmia. CONCLUSIONS: These results provide evidence of an association between ventricular arrhythmias and ambient air pollutants in St Louis. This is consistent with previous results from Boston, although the pollutants responsible for the increased risk are different.

Adult↗

PubMed2006

Bronchial hyperresponsiveness and the development of asthma and COPD in asymptomatic individuals: SAPALDIA cohort study.

BACKGROUND: Bronchial hyperresponsiveness (BHR) is a common feature of asthma. However, BHR is also present in asymptomatic individuals and its clinical and prognostic significance is unclear. We hypothesised that BHR might play a role in the development of chronic obstructive pulmonary disease (COPD) as well as asthma. METHODS: In 1991 respiratory symptoms and BHR to methacholine were evaluated in 7126 of the 9651 participants in the SAPALDIA cohort study. Eleven years later 5825 of these participants were re-evaluated, of whom 4852 performed spirometric tests. COPD was defined as an FEV1/FVC ratio of <0.70. RESULTS: In 1991 17% of participants had BHR, of whom 51% were asymptomatic. Eleven years later the prevalence of asthma, wheeze, and shortness of breath in formerly asymptomatic subjects with or without BHR was, respectively, 5.7% v 2.0%, 8.3% v 3.4%, and 19.1% v 11.9% (all p<0.001). Similar differences were observed for chronic cough (5.9% v 2.3%; p = 0.002) and COPD (37.9% v 14.3%; p<0.001). BHR conferred an adjusted odds ratio (OR) of 2.9 (95% CI 1.8 to 4.5) for wheezing at follow up among asymptomatic participants. The adjusted OR for COPD was 4.5 (95% CI 3.3 to 6.0). Silent BHR was associated with a significantly accelerated decline in FEV1 by 12 (5-18), 11 (5-16), and 4 (2-8) ml/year in current smokers, former smokers and never smokers, respectively, at SAPALDIA 2. CONCLUSIONS: BHR is a risk factor for an accelerated decline in FEV1 and the development of asthma and COPD, irrespective of atopic status. Current smokers with BHR have a particularly high loss of FEV1.

Adult↗

PubMed2006

Short-term effects of nitrogen dioxide on mortality: an analysis within the APHEA project.

The short-term effects of nitrogen dioxide (NO(2)) on total, cardiovascular and respiratory mortality in 30 European cities participating in the Air Pollution on Health: a European Approach (APHEA)-2 project were investigated. The association was examined using hierarchical models implemented in two stages. In the first stage, data from each city were analysed separately, whereas in the second stage, the city-specific air pollution estimates were regressed on city-specific covariates to obtain overall estimates and to explore sources of possible heterogeneity. A significant association of NO(2) with total, cardiovascular and respiratory mortality was found, with stronger effects on cause-specific mortality. There was evidence of confounding in respiratory mortality with black smoke and sulphur dioxide. The effect of NO(2) on total and cardiovascular mortality was observed mainly in western and southern European cities, and was larger when smoking prevalence was lower and household gas consumption was higher. The effect of NO(2) on respiratory mortality was higher in cities with a larger proportion of elderly persons in the population and higher levels of particulate matter with a 50% cut-off aerodynamic diameter of 10 mum. The results of this large study are consistent with an independent effect of nitrogen dioxide on mortality, but the role of nitrogen dioxide as a surrogate of other unmeasured pollutants cannot be completely ruled out.

Air Pollutants↗

PubMed2006

Short-term respiratory effects of cleaning exposures in female domestic cleaners.

Symptoms of obstructive lung disease in domestic cleaners have been related to the use of bleach and other irritant cleaning products. The short-term effects of cleaning exposures on respiratory symptoms and peak expiratory flow (PEF) were investigated in domestic cleaners with respiratory disorders. In a panel study, 43 female domestic cleaners with a recent history of asthma and/or chronic bronchitis completed a 2-week diary, collecting information on respiratory symptoms, PEF and cleaning exposures. Mixed regression models were used to assess daily changes in symptoms and PEF associated with specific cleaning exposures. The probability of having work-related asthma was individually assessed by a computerised diagnostic system and an occupational asthma expert. Lower respiratory tract symptoms were more common on working days and were predominantly associated with exposure to diluted bleach, degreasing sprays/atomisers and air fresheners. Associations with upper respiratory tract symptoms and PEF were less apparent. Eleven (30%) subjects scored positively for work-related asthma. It is concluded that exposure to certain irritant cleaning products aggravates lower respiratory tract symptoms in female domestic cleaners with asthma or chronic bronchitis.

Adult↗

PubMed2006

The accuracy of PillCam ESO capsule endoscopy versus conventional upper endoscopy for the diagnosis of esophageal varices: a prospective three-center pilot study.

BACKGROUND AND STUDY AIMS: Variceal bleeding is a major complication of cirrhosis, and is associated with a 20 % mortality at 6 weeks. Current international guidelines recommend that patients with cirrhosis are screened by conventional upper endoscopy (esophagogastroduodenoscopy, EGD) in order to detect esophageal varices. The recently developed PillCam ESO esophageal capsule endoscope has been shown to be an accurate diagnostic tool in the investigation of patients with gastroesophageal reflux and Barrett's esophagus. We compared the PillCam ESO capsule endoscope with EGD for the detection of esophagogastric varices and portal hypertensive gastropathy in patients with cirrhosis. PATIENTS AND METHODS: A pilot trial was conducted at three sites. Patients with cirrhosis who were undergoing clinically indicated EGD for screening or surveillance for esophageal varices underwent a PillCam ESO study followed by an EGD within 48 hours. Capsule videos were assessed by an investigator who was blinded to the patient's medical history and EGD findings. RESULTS: A total of 23 of the 32 enrolled patients were found to have esophageal varices at both EGD and PillCam ESO endoscopy. In one patient PillCam ESO detected small varices that were not seen at EGD. The overall concordance between PillCam ESO and EGD was 96.9 % for the diagnosis of esophageal varices and 90.6 % for the diagnosis of portal hypertensive gastropathy. There were no adverse events related to PillCam ESO endoscopy. CONCLUSIONS: In a high-prevalence population, PillCam ESO may represent an accurate noninvasive alternative to EGD for the detection of esophageal varices and portal hypertensive gastropathy. A large-scale trial is underway to validate and expand these findings.

Endoscopes, Gastrointestinal↗

PubMed2005

Evaluation of anemia, neutropenia and skin toxicities in standard or dose-dense doxorubicin/cyclophosphamide (AC)-paclitaxel or docetaxel adjuvant chemotherapy in breast cancer.

BACKGROUND: Results of CALGB 9741 demonstrated that administering standard doxorubicin/cyclophosphamide (AC)-paclitaxel therapy for adjuvant therapy of breast cancer in a dose-dense fashion with colony-stimulating factors increases efficacy, decreases severe neutropenia, but may increase the need for blood transfusions. A chart review was performed to evaluate the rates of anemia, neutropenia and skin toxicities with dose-dense and traditional AC-taxane chemotherapy. PATIENTS AND METHODS: A total of 112 patients received one of four treatments: non-dose-dense AC-paclitaxel (NDD Pac), dose-dense AC-paclitaxel (DD Pac), non dose-dense AC-docetaxel (NDD Doc), or dose-dense AC-docetaxel (DD Doc). RESULTS: Transfusion rates were not increased in the dose-dense population; however, rates of grade 2-4 anemia (23% versus 0%, P=0.029), as well as erythropoietin use (58% versus 0%, P <0.0001), were significantly increased in the DD Pac group compared with the NDD Pac group. Grade 3 skin toxicities were significantly increased in the DD Doc group compared with the NDD Doc group (70% versus 11%, P <0.0001). CONCLUSIONS: These results demonstrate that dose-dense AC-taxane therapy may increase rates of anemia and the need for erythropoietin, and decrease rates of neutropenia. The utility of DD Doc appears limited by skin toxicities and its use outside of a clinical study should not be recommended.

Adult↗

PubMed2005

Short term effects of particulate matter on cause specific mortality: effects of lags and modification by city characteristics.

BACKGROUND: Consistent evidence has shown increased all-cause mortality, and mortality from broad categories of causes associated with airborne particles. Less is known about associations with specific causes of death, and modifiers of those associations. AIMS: To examine these questions in 20 US cities, between 1989 and 2000. METHODS: Mortality files were obtained from the National Center for Health Statistics. Air pollution data were obtained from the Environmental Protection Agency website. The associations between daily concentrations of particulate matter of aero-diameter < or =10 microm (PM10) and daily mortality from all-cause and selected causes of death, were examined using a case-crossover design. Temporal effects of PM10 were examined using lag models, in first stage regressions. City specific modifiers of these associations were examined in second stage regressions. RESULTS: All-cause mortality increased with PM10 exposures occurring both one and two days prior the event. Deaths from heart disease were primarily associated with PM10 on the two days before, while respiratory deaths were associated with PM10 exposure on all three days. Analyses using only one lag underestimated the effects for all-cause, heart, and respiratory deaths. Several city characteristics modified the effects of PM10 on daily mortality. Important findings were seen for population density, percentage of primary PM10 from traffic, variance of summer temperature, and mean of winter temperature. CONCLUSIONS: There was overall evidence of increased daily mortality from increased concentrations of PM10 that persisted across several days, and matching for temperature did not affect these associations. Heterogeneity in the city specific PM10 effects could be explained by differences in certain city characteristics.

Air Pollutants↗

PubMed2005

Traffic related pollution and heart rate variability in a panel of elderly subjects.

BACKGROUND: Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects. METHODS: Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors. RESULTS: PM2.5 was associated with r-MSSD (-10.1% change for an interquartile range (IQR) increase in exposure (95% CI -2.8 to -16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (-4.6% per IQR (95% CI -2.0 to -7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (-12.7%, 95% CI -5.7 to -19.25). CONCLUSIONS: Particles, especially from traffic, are associated with disturbances of autonomic control of the heart.

Aged↗

PubMed2004

Myocarditis susceptibility in female mice depends upon ovarian cycle phase at infection.

Female BALB/c mice were infected with coxsackievirus B3 in the diestrus, proestrus, estrus, or metestrus phases of the ovarian cycle. Cycle stage was determined by vaginal smear. All mice were killed 7 days after infection. Females infected in the diestrus and especially the proestrus phases developed myocarditis. CD4+ T cells expressing interferon-gamma (IFNgamma) infiltrate the myocardium in these two phases, whereas CD4+ T cells expressing IL-4 are more frequent during estrus. Cardiac virus titers were determined 15 h and 7 days after infection. No differences in virus titer were seen at 7 days. These studies show that natural hormone variations can have substantial effects on viral pathogenicity presumably due to hormone effects on the immune system.

Animals↗

PubMed2004

Early embryonic environment, the fetal pituitary-adrenal axis and the timing of parturition.

It is well established in the sheep, that the normal timing of parturition is dependent on a prepartum activation of the fetal pituitary-adrenal axis. We have recently demonstrated for the first time that embryo number, embryo sex, and alterations in the environment of the early embryo, including exposure to maternal undernutrition during the periconceptional period, alter the timing and level of activation of the pituitary-adrenal axis in the sheep fetus during late gestation. There is a delay in activation of the fetal HPA axis in twin fetuses and we speculate that the diminished adrenocortical responsiveness in the twin fetus may be an adaptive response, which counters the impact of the potential enhanced intrauterine stress experienced by a twin fetus, thereby reducing the possibility of preterm delivery. We have also reported that a moderate restriction of maternal nutrition to during the periconceptional period (from 60 days before and for one week after conception) resulted in an earlier activation of the pituitary-adrenal axis of twin, but not singleton, fetuses during late gestation. A series of studies using assisted reproductive technologies have also found that perturbation of the early embryonic environment results in a dysregulation of placental and fetal growth and development and in the timing of normal parturition. In summary, after several decades of work focussed on events in late gestation associated with the prepartum activation and stress responsiveness of the fetal HPA axis, our recent studies indicate that the environment of the early embryo may have a significant role to play in determining the timing and level of the prepartum activation of this axis and potentially on the functional capacity of the axis to respond to acute or chronic stress in later life.

Animals↗

PubMed2004

The effect of practical portion size measurement aids on the accuracy of portion size estimates made by young adults.

A barrier to controlling the amount of food consumed may be the difficulty consumers have in accurately estimating portion sizes. Although portion size measurement aids (PSMAs) can improve estimation accuracy, their bulk and/or cost tends to make them impractical for regular use. The purpose of this study was to investigate the effect on portion size estimation accuracy of two practical PSMAs: a 2-D PSMA (life size picture of tennis and golf balls) and 3-D PSMAs (tennis and golf balls). Young adults were randomly assigned to one of two groups and estimated the portion sizes of 36 foods divided into three equal sets. PSMAs were not used to estimate portion sizes in Food Set 1. Study group 1 (n = 57) used the 2-D PSMA and study group 2 (n = 56) used the 3-D PSMAs to estimate the portion sizes in Food Set 2. Neither group used PSMAs to estimate portion sizes in Food Set 3. Repeated measures anova indicated that both groups significantly improved estimation accuracy between Food Sets 1 and 2 and between Foods Sets 1 and 3. Thus, even short-term exposure to practical PSMAs may improve estimation accuracy and these improvements persist when the PSMA is no longer available. However, the accuracy rate for Food Set 2 was only about 60% indicating that a great deal of estimation error remains.

Adolescent↗

PubMed2004

Apheis: public health impact of PM10 in 19 European cities.

STUDY OBJECTIVE: Apheis is a public health surveillance system that aims to provide European, national, regional, and local decision makers, environmental health professionals, and the general public with up to date and easy to use information on air pollution and public health. This study presents the health impact assessment done in 19 cities of Western and Eastern European countries. DESIGN: Apheis developed guidelines for gathering and analysing data on air pollution and the impact on public health. Apheis has analysed the acute and chronic effects of fine particles on premature mortality using the estimates developed by Aphea2 study and two American cohort studies. This health impact assessment was performed for different scenarios on the health benefits of reducing levels of particles less than 10 microm in size (PM(10)). MAIN RESULTS: PM(10) concentrations were measured in 19 cities (range: 14-73 microg/m(3)). The population covered in this health impact assessment includes nearly 32 million inhabitants. The age standardised mortality rates (per 100 000 people) range from 456 in Toulouse to 1127 in Bucharest. Reducing long term exposure to PM(10) concentrations by 5 microg/m(3) would have "prevented" between 3300 and 7700 early deaths annually, 500 to 1000 of which are associated with short term exposure. CONCLUSIONS: Apheis shows that current levels of air pollution in urban Europe have a non-negligible impact on public health, and that preventive measures could reduce this impact, even in cities with low levels of air pollution.

Air Pollutants↗

PubMed2004

The effects of particulate air pollution on daily deaths: a multi-city case crossover analysis.

BACKGROUND: Numerous studies have reported that day-to-day changes in particulate air pollution are associated with day-to-day changes in deaths. Recently, several reports have indicated that the software used to control for season and weather in some of these studies had deficiencies. AIMS: To investigate the use of the case-crossover design as an alternative. METHODS: This approach compares the exposure of each case to their exposure on a nearby day, when they did not die. Hence it controls for seasonal patterns and for all slowly varying covariates (age, smoking, etc) by matching rather than complex modelling. A key feature is that temperature can also be controlled by matching. This approach was applied to a study of 14 US cities. Weather and day of the week were controlled for in the regression. RESULTS: A 10 microg/m3 increase in PM10 was associated with a 0.36% increase in daily deaths from internal causes (95% CI 0.22% to 0.50%). Results were little changed if, instead of symmetrical sampling of control days the time stratified method was applied, when control days were matched on temperature, or when more lags of winter time temperatures were used. Similar results were found using a Poisson regression, but the case-crossover method has the advantage of simplicity in modelling, and of combining matched strata across multiple locations in a single stage analysis. CONCLUSIONS: Despite the considerable differences in analytical design, the previously reported associations of particles with mortality persisted in this study. The association appeared quite linear. Case-crossover designs represent an attractive method to control for season and weather by matching.

Air Pollution↗