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Table 2 Estimated percentage point change in the mean prevalence of e-cigarette users among tobacco smokers who endorse the belief that e-cigarettes are less harmful than combustible cigarettes during the study period (2014–2019), based on autoregressive integrated moving average with exogenous input (ARIMAX) models stratified by age, sex and social grade

From: Association between changes in harm perceptions and e-cigarette use among current tobacco smokers in England: a time series analysis

 16–24 years25–64 years65+ years
Unadjusted
(95% CI,pvalue)
Adjusted
(95% CI,pvalue)
Unadjusted
(95% CI,pvalue)
Adjusted
(95% CI,pvalue)
Unadjusted
(95% CI,pvalue)
Adjusted
(95% CI,pvalue)
Percentage change per 1% change in the mean prevalence of the exposure
  Use of e-cigarettes0.12 (− 0.15–0.38), 0.390.13 (− 0.12–0.39), 0.310.42 (0.17–0.66), < 0.0010.37 (0.13–0.61), < 0.010.22 (0.08–0.36), < 0.010.22 (0.07–0.37), < 0.01
  Current cigarette smokers− 0.14 (− 0.38–0.10), 0.250.01 (− 0.23–0.24), 0.96− 0.03 (− 0.25–0.19), 0.78
  Tried to quit in the past year0.17 (− 0.08–0.43), 0.180.18 (− 0.07–0.42), 0.15− 0.11 (− 0.34–0.13), 0.37
  National mass media expenditure in millions (£)− 0.11 (− 0.38–0.16), 0.430.16 (− 0.10–0.41), 0.230.08 (− 0.16–0.32), 0.50
Best fitting model
  ARIMAX (p,d,q)(P,D,Q)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)
  Non-seasonal (p value)      
   Autoregressive (AR) term
   Moving average (MA) term< 0.001< 0.001< 0.001< 0.001< 0.001< 0.001
  Pseudo R20.020.080.170.230.280.29
 MenWomen  
 UnadjustedAdjustedUnadjustedAdjusted  
Percentage change per 1% change in the mean prevalence of the exposure
  Use of e-cigarettes0.42 (0.18–0.66), < 0.0010.48 (0.18–0.78), < 0.010.21 (− 0.07–0.49), 0.140.13 (− 0.12–0.38), 0.29  
  Current cigarette smokers− 0.21 (− 0.44–0.02), 0.080.13 (− 0.08–0.34), 0.23  
  Tried to quit in the past year0.18 (− 0.06–0.42), 0.150.37 (0.13–0.61), < 0.01  
  National mass media expenditure in millions (£)0.27 (− 0.08–0.62), 0.130.08 (− 0.17–0.33), 0.52  
Best fitting model
  ARIMAX (p,d,q)(P,D,Q)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)  
  Non-seasonal (p value)      
   Autoregressive (AR) term  
   Moving average (MA) term< 0.001< 0.001< 0.001< 0.001  
  Pseudo R20.230.250.160.31  
 ABC1C2DE  
 UnadjustedAdjustedUnadjustedAdjusted  
Percentage change per 1% change in the mean prevalence of the exposure
  Use of e-cigarettes0.50 (0.28–0.72), < 0.0010.49 (0.27–0.71), < 0.0010.43 (0.18–0.67), < 0.0010.37 (0.12–0.61), < 0.01  
  Current cigarette smokers0.06 (− 0.16–0.27), 0.59− 0.05 (− 0.28–0.18), 0.68  
  Tried to quit in the past year0.06 (− 0.17–0.29), 0.610.28 (0.04–0.52), 0.02  
  National mass media expenditure in millions (£)0.15 (− 0.08–0.38), 0.210.07 (− 0.19–0.32), 0.60  
Best fitting model
  ARIMAX (p,d,q)(P,D,Q)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)(0,1,1)(0,0,0)  
  Non-seasonal (p value)      
   Autoregressive (AR) term  
   Moving average (MA) term< 0.001< 0.001< 0.001< 0.001  
  Pseudo R20.270.300.190.27