Table 7 Summary of all-cause mortality odds ratios (OR), excess risk (ER), and additive interaction indicators for co-exposure to days extreme PM2.5 and/or extreme temperature ( > 90th percentile)

From: The synergistic effects of PM2.5 and high temperature on community mortality in British Columbia

 

Point Estimates [95% CI]

OR for Exposurea

 No extreme PM2.5 or temperature ( < 50th percentile)

Ref

 Extreme PM2.5 only ( > 90th percentile)

1.02 [0.96, 1.09]

 Extreme temperature only ( > 90th percentile)

1.06 [1.01, 1.11]

 Extreme PM2.5 and temperature ( > 90th percentile)

1.51 [1.41, 1.62]

Percent ER of Community Mortalityb

 Extreme PM2.5 only ( > 90th percentile)

0.11 [−1.1, 1.4]

 Extreme temperature only ( > 90th percentile)

1.3 [0.14, 2.3]

 Extreme PM2.5 and temperature ( > 90th percentile)

7.9 [6.1, 9.1]

Indicators of Additive Interactionc

 Relative Excess Odds due to Interaction (REOI)

0.430 [0.294, 0.567]

 Proportion Attributable to Interaction (AP)

0.843 [0.576, 1.111]

 Synergy Index (S)

6.38 [−0.316, 13.08]

  1. aPoint estimates and 95% CIs for the exposure categories are Odds Ratios estimated from conditional logistic regression.
  2. bPoint estimates for excess risk and 95% CIs were estimated using a bootstrap method with 1000 iterations described by Richardson and Kaufman (2009)74.
  3. cPoint estimates and 95% CI were estimated for relative excess odds due to interaction (REOI), proportion attributable to interaction (AP), and synergy index (S) using the approach described in Knol and VanDerweele (2012)72. We defined significant synergistic effects when REOI > 0, AP > 0, and S > 1.
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