Table 1

Odds ratios of linear and quadratic models for ever smoked and regular smoking between 1998–2015 among students in England, Scotland and Wales

Ever smokedRegular smoking
LinearP valueQuadraticP valueLinearP valueQuadraticP value
Whole sample
(n=242 855; 243 111)
Year0.91 (0.91 to 0.91)<0.0010.95 (0.93 to 0.96)<0.0010.93 (0.93 to 0.94)<0.0010.98 (0.96 to 1.00)0.025
Year2 1.00 (1.00 to 1.00)<0.0011.00 (1.00 to 1.00)<0.001
Level0.89 (0.84 to 0.95)<0.0010.89 (0.84 to 0.95)<0.0010.79 (0.71 to 0.88)<0.0010.80 (0.72 to 0.90)<0.001
Post-slope0.97 (0.96 to 0.99)<0.0011.01 (0.99 to 1.03)0.2310.98 (0.96 to 1.01)0.2311.04 (1.00 to 1.08)0.028
Male only subgroup
(n=121 879; 122 042)
Year0.92 (0.92 to 0.93)<0.0010.93 (0.91 to 0.95)<0.0010.94 (0.94 to 0.95)<0.0010.95 (0.92 to 0.98)<0.001
Year2 1.00 (1.00 to 1.00)0.6211.00 (1.00 to 1.00)0.583
Level0.88 (0.81 to 0.96)0.0050.88 (0.81 to 0.96)0.0050.83 (0.70 to 0.97)0.0220.83 (0.70 to 0.97)0.023
Post-slope0.98 (0.95 to 1.00)0.0340.98 (0.95 to 1.01)0.2121.00 (0.96 to 1.04)0.9211.01 (0.96 to 1.06)0.794
Female only subgroup
(n=120 976; 121 069)
Year0.90 (0.89 to 0.90)<0.0010.96 (0.94 to 0.98)<0.0010.92 (0.92 to 0.93)<0.0011.00 (0.98 to 1.03)0.922
Year2 1.00 (0.99 to 1.00)<0.0010.99 (0.99 to 1.00)<0.001
Level0.90 (0.83 to 0.98)0.0140.90 (0.83 to 0.98)0.0180.76 (0.65 to 0.89)<0.0010.78 (0.67 to 0.91)0.002
Post–slope0.97 (0.95 to 0.99)0.0091.05 (1.01 to 1.08)0.0030.97 (0.93 to 1.01)0.1391.07 (1.02 to 1.12)0.009
13 year olds only
(n=126 960; 127 100)
Year0.89 (0.89 to 0.90)<0.0010.96 (0.94 to 0.98)<0.0010.91 (0.90 to 0.92)<0.0011.02 (0.98 to 1.05)0.378
Year2 1.00 (0.99 to 1.00)<0.0010.99 (0.99 to 1.00)<0.001
Level0.82 (0.74 to 0.91)<0.0010.83 (0.75 to 0.92)<0.0010.73 (0.57 to 0.92)0.0090.76 (0.60 to 0.97)0.027
Post-slope0.99 (0.96 to 1.01)0.3041.07 (1.03 to 1.10)<0.0011.00 (0.95 to 1.07)0.9021.14 (1.06 to 1.23)<0.001
15 year olds only
(n=115 895; 116 011)
Year0.93 (0.93 to 0.93)<0.0010.94 (0.92 to 0.95)<0.0010.94 (0.93 to 0.94)<0.0010.97 (0.95 to 0.99)0.003
Year2 1.00 (1.00 to 1.00)0.3901.00 (1.00 to 1.00)0.009
Level0.92 (0.85 to 0.99)0.0350.92 (0.85 to 0.99)0.0360.79 (0.70 to 0.90)<0.0010.80 (0.70 to 0.90)<0.001
Post-slope0.96 (0.94 to 0.98)<0.0010.96 (0.94 to 0.99)0.0120.98 (0.95 to 1.01)0.2401.01 (0.97 to 1.06)0.497