Skip to main content

Table 3 Primary analysis—results of the GAM analyses fitting linear trends to current smoking status, ever smoking status, and quit attempts among past-year smokers (16–17 versus 18–24 year olds)

From: Long-term evaluation of the rise in legal age-of-sale of cigarettes from 16 to 18 in England: a trend analysis

 

Unadjusted

Adjusted for sex and social grade and population-level policies

OR

95%CI

p

BFs

OR

95%CI

p

BFs

Lower

Upper

Lower

Upper

Current smoking

 Trend

0.982

0.956

1.008

0.179

 

0.979

0.954

1.006

0.127

 

 Level

0.903

0.670

1.218

0.504

 

0.807

0.456

1.426

0.460

 

 Change in slope

1.012

0.985

1.039

0.389

 

1.012

0.986

1.041

0.364

 

 Age (16–17 ref)

1.922

1.523

2.426

< 0.001

 

1.953

1.542

2.475

< 0.001

 

 Level × age

1.113

0.838

1.378

0.458

0.80

1.103

0.827

1.472

0.504

0.75

 Slope × age

1.001

0.999

1.004

0.233

1.22

1.002

0.999

1.004

0.141

2.10

Ever smoking

 Trend

0.981

0.955

1.007

0.145

 

0.978

0.953

1.004

0.103

 

 Level

0.950

0.713

1.267

0.727

 

0.899

0.520

1.552

0.702

 

 Change in slope

1.012

0.986

1.039

0.358

 

1.012

0.985

1.040

0.374

 

 Age (16–17 ref)

2.116

1.690

2.649

< 0.001

 

2.139

1.703

2.686

< 0.001

 

 Level × age

1.044

0.785

1.371

0.755

0.52

1.036

0.786

1.366

0.803

0.50

 Slope × age

1.002

1.000

1.005

0.040

2.10

1.003

1.000

1.005

0.019

4.20

Trend after 16–17

0.993

0.942

1.046

  

0.990

0.939

1.044

  

Trend after 18–24

0.995

0.942

1.052

  

0.993

0.939

1.049

  

Quit attempts

 Trend

0.985

0.945

1.027

0.485

 

0.984

0.944

1.027

0.464

 

 Level

0.529

0.322

0.902

0.019

 

0.311

0.117

0.825

0.019

 

 Change in slope

1.011

0.970

1.055

0.598

 

1.014

0.971

1.058

0.526

 

 Age (16–17 ref)

0.587

0.394

0.874

0.009

 

0.585

0.393

0.872

0.009

 

 Level × age

1.770

1.081

2.899

0.023

5.68

1.760

1.075

2.884

0.025

5.49

 Slope × age

0.998

0.994

1.003

0.440

0.71

0.998

0.994

1.003

0.460

0.71

Level 16–17

0.529

0.322

0.902

  

0.311

0.117

0.825

  

Level 18–24

0.936

0.348

2.615

  

0.547

0.126

2.379

  
  1. BFs Bayes factors; the ORs representing the main effects for level and slope (i.e. β3level and β4slope) can be interpreted as the effect among 16–17 year olds, while the effect among the comparison groups is calculated as the main effects multiplied by the ORs for the interactions (i.e. β3level × (β5levelt × age) and β4slope × (β6slope × age))