Referent Selection in Case-Crossover Analyses of Acute Health Effects of Air Pollution

Levy, Drew; Lumley, Thomas; Sheppard, Lianne; Kaufman, Joel D.; Checkoway, Harvey

doi:10.1097/00001648-200103000-00010

Cited by 442 publications

(366 citation statements)

References 16 publications

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“…44 Thereby, each subject's exposure prior to a case-defining event is compared with his or her own exposure during a control period when he/she had not yet been diagnosed as a case. A case day was the day on which the first symptom of mumps presented, 45,46 and the case period was 0-14 d prior to that day. The control day was selected 2 to 4 weeks before the case date (14-28 d prior to the case day).…”

Section: Discussionmentioning

confidence: 99%

The association between the incidence of mumps and meteorological parameters in Taiwan

et al. 2015

Human Vaccines & Immunotherapeutics

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These authors equally contributed to this work. Keywords: infectious disease, meteorological parameters, modeling, mumps, weatherMumps is caused by a paramyxovirus. It is an acute, but mild infectious disease. However, approximately 10% of patients with mumps can develop severe meningoencephalitis, disability, and death. Seasonal patterns in mumps vary across countries, but the reasons for this phenomenon remain unclear. The aim of this study was to assess the role of meteorological factors on mumps infection. We investigated the relationships between weather variability and the incidence of mumps in Taiwan using a Poisson regression analysis and case-crossover methodology. Between 2006 and 2011, 6,612 cases of mumps were reported to the Centers for Disease Control, Taiwan (Taiwan CDC). The incidence of mumps showed a significant seasonality in summertime (for oscillation, P < 0.001). The number of mumps started to increase at temperatures of 20 C (r 2 D 0.73, P < 0.001), and the case count of mumps began to decline when the temperatures were higher than approximately 25 C (r 2 D 0.24, p D 0.04), producing an inverted V-shaped relationship. Similarly, the number of mumps began to increase at a vapor pressure of 5-9 hPa (r 2 D 0.87, P < 0.005) and decreased at a vapor pressure higher than 25-29 hPa (r 2 D 0.21, p D 0.05). The number of mumps cases was positively associated with temperature and vapor pressure in the preceding period of the infection. In conclusion, this study showed that the occurrence of mumps is significantly associated with increasing temperature and vapor pressure in Taiwan. Therefore, these factors could be regarded as warning signals indicating the need to implement preventive measures.

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Section: Discussionmentioning

confidence: 99%

The association between the incidence of mumps and meteorological parameters in Taiwan

et al. 2015

Human Vaccines & Immunotherapeutics

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“…The study was conducted under a time-stratified casecrossover design, which is used to assess brief changes in risk associated with transient exposures [3,4]. Casecrossover analyses require exposure data for cases only.…”

Section: Methodsmentioning

confidence: 99%

Association between PM2.5 and primary care visits due to asthma attack in Japan: relation to Beijing’s air pollution episode in January 2013

Yamazaki

Shima

Yoda

et al. 2013

Environ Health Prev Med

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Aim In January 2013, extremely high concentrations of fine particles (PM 2.5 ) were observed around Beijing, China. In Japan, the health effects of transboundary air pollution have been a matter of concern. We examined the association between the levels of outdoor PM 2.5 and other air pollutants with primary care visits (PCVs) at night due to asthma attack in Himeji City, western Japan. Methods A case-crossover study was conducted in a primary care clinic in Himeji City, Japan, involving 112 subjects aged 0-80 years who visited the clinic due to an asthma attack between 9 p.m. and 6 a.m. during the period January-March, 2013. Daily concentrations of particulate matter, ozone, nitrogen dioxide, and some meteorological elements were measured, and a conditional logistic regression model was used to estimate the odds ratios (OR) of PCVs per unit increment in air pollutants or meteorological elements. Results Of the 112 subjects, 76 (68 %) were aged \15 years. We did not note any association between daily PM 2.5 levels and PCVs due to asthma attack at night. A positive relation between ozone and PCVs due to asthma attack was detected. The OR per 10 ppb increment in daily mean ozone the day before the visit was 2.31 (95 % confidence interval 1.16-4.61). Conclusion These findings do not support an association between daily mean concentration of PM 2.5 and PCVs at night. However, we did find evidence suggesting that ozone is associated with PCVs.

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“…I started with the timestratified control sampling scheme recommended by Levy et al (2001a), where control days for an event are all of the other days of the same month of the same year. I then restricted those to a subset that was also matched on concentration of a gaseous air pollutant.…”

Section: Methodsmentioning

confidence: 99%

“…Several approaches have been shown to address this problem, and in this study I use the time-stratified approach of Levy et al (2001a).…”

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confidence: 99%

Is the association of airborne particles with daily deaths confounded by gaseous air pollutants? An approach to control by matching.

Schwartz

2004

Environ Health Perspect

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Although particulate air pollution has been associated with increased numbers of daily deaths in dozens of cities around the world, issues still remain about the association. Some have questioned the complex modeling used to control for season in Poisson regression or the role of gaseous air pollutants as potential confounders of the association. I examined the association between deaths and particulate matter with an aerodynamic diameter ≤ 10 µm (PM 10 ) using a case-crossover design. In this approach, the pollution on the day of each death is contrasted with the pollution level on control days when the subject did not die. Season and gaseous air pollutants were controlled by matching. Control days were chosen within the same month of the same year to control for season, and matched on either sulfur dioxide (SO 2 ; within 1 ppb), nitrogen dioxide (within 1 ppb), maximum ozone (within 2 ppb), or carbon monoxide (within 0.03 ppm). The analysis was conducted in 14 U.S. cities that have daily PM 10 monitoring. After matching, there were about 400,000 deaths in each analysis. Results were combined across cities using a maximum likelihood method. PM 10 was a significant predictor of mortality when controlling for gaseous air pollutants, with effect sizes ranging from a 0.45% increase per 10 µg/m 3 increment of PM 10 [95% confidence interval (CI), 0.12-0.79%] when matched on maximum hourly ozone levels, to a 0.81% increase per 10 µg/m 3 increment of PM 10 (95% CI, 0.47-1.16%) when matched on 24-hr average SO 2 .

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Referent Selection in Case-Crossover Analyses of Acute Health Effects of Air Pollution

Cited by 442 publications

References 16 publications

The association between the incidence of mumps and meteorological parameters in Taiwan

The association between the incidence of mumps and meteorological parameters in Taiwan

Association between PM2.5 and primary care visits due to asthma attack in Japan: relation to Beijing’s air pollution episode in January 2013

Is the association of airborne particles with daily deaths confounded by gaseous air pollutants? An approach to control by matching.

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