further corrections to formula for combining tobacco and alcohol risk

STAPM · Jun 1, 2023 · 2ee21a8 · 2ee21a8
1 parent 7bcb294
commit 2ee21a8
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Showing 2 changed files with 5 additions and 3 deletions.
diff --git a/R/RRFunc.R b/R/RRFunc.R
@@ -771,15 +771,17 @@ RRFunc <- function(
 
         # Combine the tobacco and alcohol relative risks
         # accounting for the synergy index
-        data[ , (d) := (1 + ((get(d_alc) - 1) + (get(d_tob) - 1)) * get(d_si))]
+        #data[ , (d) := (1 + ((get(d_alc) - 1) + (get(d_tob) - 1)) * get(d_si))]
+        data[ , (d) := get(d_alc) * get(d_tob) * get(d_si)] # formula changed to align with corrected formula for the synergy index from Prabhu Am J Gastroenterol 2014; 109:822–827; doi: 10.1038/ajg.2014.71
 
         data[ , (d_si) := NULL]
 
       } else { # If synergy should not be accounted for
 
         # Combine the tobacco and alcohol relative risks
         # *without* accounting for the synergy index
-        data[ , (d) := 1 + ((get(d_alc) - 1) + (get(d_tob) - 1))]
+        #data[ , (d) := 1 + ((get(d_alc) - 1) + (get(d_tob) - 1))]
+        data[ , (d) := get(d_alc) * get(d_tob)]
 
       }
 

diff --git a/R/TobAlcInt.R b/R/TobAlcInt.R
@@ -74,7 +74,7 @@ TobAlcInt <- function(
     alc1_tob1 <- rr[ , alc1_tob1]
 
     #si <- (alc1_tob1 - 1) / ((alc1_tob0 - 1) + (alc0_tob1 - 1))
-    si <- alc1_tob1 / (alc1_tob0 + alc0_tob1)
+    si <- alc1_tob1 / (alc1_tob0 * alc0_tob1) # corrected to match Prabhu Am J Gastroenterol 2014; 109:822–827; doi: 10.1038/ajg.2014.71;
 
   } else {