G R Cohen

Publications of G R Cohen

• Interacting effects of particulate pollution and cold temperature on cardiorespiratory mortality in Scotland.

  Authors: M Carder, R McNamee, I Beverland, R Elton, M van Tongeren, G R Cohen, J Boyd, W Macnee, R M Agius

  Occupational and environmental medicine. 04/2008; 65(3):197-204.

  OBJECTIVES: To determine whether the effect of black smoke on cardiorespiratory mortality is modified by cold temperatures. METHODS: Poisson regression models were used to investigate theOBJECTIVES: To determine whether the effect of black smoke on cardiorespiratory mortality is modified by cold temperatures. METHODS: Poisson regression models were used to investigate the relationship between lagged black smoke concentration and daily mortality, and whether the effect of black smoke on mortality was modified by cold temperature for three Scottish cities from January 1981 to December 2001. MAIN RESULTS: For all-cause respiratory and non-cardiorespiratory mortality, there was a significant association between mortality and lagged black smoke concentration. Generally the maximum black smoke effect occurred at lag 0, although these estimates were not statistically significant. A 10 mugm(-3) increase in the daily mean black smoke concentration on any given day was associated with a 1.68% (95% CI 0.72 to 2.65) increase in all-cause mortality and a 0.43% (95% CI -0.97 to 1.86), 5.36% (95% CI 2.93 to 7.84) and 2.13% (95% CI 0.82 to 3.47) increase in cardiovascular, respiratory and non-cardiorespiratory mortality, respectively, over the ensuing 30-day period. The effect of black smoke on mortality did not vary significantly between seasons (cool and warm periods). For all-cause, cardiovascular and non-cardiorespiratory mortality the inclusion of interaction terms did not improve the models, although for all-cause and non-cardiorespiratory mortality there was a suggestion for interaction between temperature and recent black smoke exposure. CONCLUSIONS: The results of this study suggested a greater effect of black smoke on mortality at low temperatures. Since extremes of cold and particulate pollution may coexist, for example during temperature inversion, these results may have important public health implications.

• The lagged effect of cold temperature and wind chill on cardiorespiratory mortality in Scotland.

  Authors: M Carder, R McNamee, I Beverland, R Elton, G R Cohen, J Boyd, R M Agius

  Occupational and environmental medicine. 11/2005; 62(10):702-10.

  AIMS: To investigate the lagged effects of cold temperature on cardiorespiratory mortality and to determine whether "wind chill" is a better predictor of these effects than "dry bulb" temperature.AIMS: To investigate the lagged effects of cold temperature on cardiorespiratory mortality and to determine whether "wind chill" is a better predictor of these effects than "dry bulb" temperature. METHODS: Generalised linear Poisson regression models were used to investigate the relation between mortality and "dry bulb" and "wind chill" temperatures in the three largest Scottish cities (Glasgow, Edinburgh, and Aberdeen) between January 1981 and December 2001. Effects of temperature on mortality (lags up to one month) were quantified. Analyses were conducted for the whole year and by season (cool and warm seasons). MAIN RESULTS: Temperature was a significant predictor of mortality with the strongest association observed between temperature and respiratory mortality. There was a non-linear association between mortality and temperature. Mortality increased as temperatures fell throughout the range, but the rate of increase was steeper at temperatures below 11 degrees C. The association between temperature and mortality persisted at lag periods beyond two weeks but the effect size generally decreased with increasing lag. For temperatures below 11 degrees C, a 1 degrees C drop in the daytime mean temperature on any one day was associated with an increase in mortality of 2.9% (95% CI 2.5 to 3.4), 3.4% (95% CI 2.6 to 4.1), 4.8% (95% CI 3.5 to 6.2) and 1.7% (95% CI 1.0 to 2.4) over the following month for all cause, cardiovascular, respiratory, and "other" cause mortality respectively. The effect of temperature on mortality was not observed to be significantly modified by season. There was little indication that "wind chill" temperature was a better predictor of mortality than "dry bulb" temperature. CONCLUSIONS: Exposure to cold temperature is an important public health problem in Scotland, particularly for those dying from respiratory disease.

• Investigation of factors which might indicate susceptibility to particulate air pollution.

  Authors: G J Prescott, R J Lee, G R Cohen, R A Elton, A J Lee, F G Fowkes, R M Agius

  Occupational and environmental medicine. 02/2000; 57(1):53-7.

  OBJECTIVES: To determine whether previous symptoms or recognized risk factors of cardiovascular ill health, are associated with an increased likelihood of adverse health effects related toOBJECTIVES: To determine whether previous symptoms or recognized risk factors of cardiovascular ill health, are associated with an increased likelihood of adverse health effects related to particulate air pollution. METHODS: Cardiovascular event rates were studied relative to urban concentrations of particulate air pollution and baseline risk factors. The Edinburgh artery study consisted of a cohort of 1592 subjects aged 55-74 and was followed up to the end of March 1998 for a median of 10 years resulting in about 5 million person-days of observation. Baseline measurements included plasma fibrinogen and blood and plasma viscosity. A nested case-control approach was used to investigate a possible interaction between effects of these selected baseline risk factors and particulate air pollution, on subsequent event rates. RESULTS: During the follow up period there were 343 fatal and non-fatal myocardial infarctions or strokes. Trends in adverse cardiovascular outcomes related to pollution were identified among subjects belonging to the highest baseline quintile of plasma fibrinogen. Evidence for interactions between concentrations of particulate pollution and fibrinogen was not established at conventional levels of significance. CONCLUSIONS: People with high concentrations of plasma fibrinogen might be more susceptible to adverse cardiovascular effects of particulate air pollution, but limitations of power mean that evidence relating to such an interaction is not conclusive. A range of cardiopulmonary risk factors warrant investigation in relation to possible susceptibility to air pollution.

• Urban air pollution and cardiopulmonary ill health: a 14.5 year time series study.

  Authors: G J Prescott, G R Cohen, R A Elton, F G Fowkes, R M Agius

  Occupational and environmental medicine. 11/1998; 55(10):697-704.

  OBJECTIVES: To examine possible associations between daily concentrations of urban air pollutants and hospital emergency admissions and mortality due to cardiac and pulmonary disease. METHODS: A timeOBJECTIVES: To examine possible associations between daily concentrations of urban air pollutants and hospital emergency admissions and mortality due to cardiac and pulmonary disease. METHODS: A time series study was conducted in the City of Edinburgh, which has a population of about 450,000. Poisson log linear regression models were used to investigate the relation of the daily event rate with daily air pollution concentrations of sulphur dioxide (SO2) and black smoke from 1981 to 1995, and of nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and particulate matter (PM10) from 1992 to 1995. Adjustments were made for seasonal and weekday variation, daily temperature, and wind speed. RESULTS: The most significant findings were positive associations over the period 1981-95 between black smoke as a mean of the previous three days and daily all cause mortality in people aged > or = 65, and respiratory mortality also in this age group (3.9% increase in mortality for a 10 micrograms/m3 increment in black smoke). For hospital emergency admissions between 1992 and 1995 the two most significant findings (p < 0.05) were for cardiovascular admissions of people aged > or = 65 which showed a positive association with PM10 as a mean of the 3 previous days, and a negative association with O3 as a mean of the previous three days. Analyses of outcomes based on linkage with previous cardiorespiratory emergency admissions did not show substantially different results. CONCLUSION: These data suggest that in the City of Edinburgh, after correction for confounders, there was a small but significant association between concentrations of black smoke and respiratory mortality in the older age group, probably attributable to higher pollution levels in the early part of the study period. There were also generally weak and variable associations between day to day changes in concentrations of urban air pollutants at a single central point and emergency hospital admission rates from cardiac and respiratory disease.

• Mid-P confidence intervals for the Poisson expectation.

  Authors: G R Cohen, S Y Yang

  Statistics in medicine. 12/1994; 13(21):2189-203.

  Conventionally a confidence interval (CI) for the standardized mortality ratio is set using the conservative CI for a Poisson expectation, mu. Employing the mid-P argument we present alternative CIsConventionally a confidence interval (CI) for the standardized mortality ratio is set using the conservative CI for a Poisson expectation, mu. Employing the mid-P argument we present alternative CIs that are shorter than the conventional ones. The mid-P intervals do not guarantee the nominal confidence level, but the true coverage probability is only lower than the nominal level for a few short ranges of mu. The implications for mid-P confidence intervals of various proposed definitions of two-sided tests for discrete data are discussed.

• Epidemiological Study of Susceptibility to Cardiorespiratory Death from Particulate Air Pollution

  Authors: R M Agius, G R Cohen, I Beverland, R A Elton, R. Lee, J Boyd

  We conducted a 17 yr time series of mortality in urban elderly populations associated with black smoke (BS) pollution in relation to prior cardiorespiratory emergency hospital admission as a possibleWe conducted a 17 yr time series of mortality in urban elderly populations associated with black smoke (BS) pollution in relation to prior cardiorespiratory emergency hospital admission as a possible index of susceptibility. There were significant associations between BS and all cause mortality in Glasgow and Edinburgh and these were largest following respiratory admissions in those who survived more than 3 yr after their last discharge. These data suggest that emergency hospital admission with respiratory disease may indicate subsequent increasing susceptibility to particulate air pollution.