Table 2

Odds ratios of linear and quadratic models for smoking attitudes among students in England and Scotland (trying smoking is ‘OK’, from 1999 to 2015) and England only (smoking weekly is ‘OK’, from 2003 to 2014)

		Trying smoking is OK* (don’t know=not OK)				Smoking weekly is OK† (don’t know=not OK)
		Linear	P value	Quadratic	P value	Linear	P value	Quadratic	P value
Whole sample (n=165 199; 35 890)	Year	0.91 (0.91 to 0.92)	<0.001	0.87 (0.85 to 0.89)	<0.001	0.91 (0.90 to 0.92)	<0.001	0.72 (0.65 to 0.81)	<0.001
	Year²	–	–	1.00 (1.00 to 1.00)	<0.001	–	–	1.01 (1.01 to 1.02)	<0.001
	Level	1.03 (0.97 to 1.10)	0.330	1.05 (0.98 to 1.12)	0.143	1.15 (1.00 to 1.32)	0.045	1.10 (0.96 to 1.27)	0.152
	Post-slope	0.92 (0.90 to 0.93)	<0.001	0.88 (0.86 to 0.90)	<0.001	0.95 (0.90 to 1.00)	0.032	0.82 (0.75 to 0.89)	<0.001
Male only subgroup (n=82 270; 18 042)	Year	0.92 (0.91 to 0.93)	<0.001	0.84 (0.81 to 0.87)	<0.001	0.92 (0.91 to 0.94)	<0.001	0.67 (0.57 to 0.79)	<0.001
	Year²	–	–	1.01 (1.00 to 1.01)	<0.001	–	–	1.02 (1.01 to 1.03)	<0.001
	Level	1.08 (0.99 to 1.18)	0.090	1.11 (1.01 to 1.22)	0.024	1.33 (1.10 to 1.62)	0.004	1.27 (1.04 to 1.54)	0.020
	Post-slope	0.91 (0.89 to 0.93)	<0.001	0.84 (0.81 to 0.88)	<0.001	0.88 (0.82 to 0.94)	<0.001	0.71 (0.62 to 0.81)	<0.001
Female only subgroup (n=82 929; 17 848)	Year	0.90 (0.90 to 0.91)	<0.001	0.89 (0.86 to 0.93)	<0.001	0.90 (0.88 to 0.91)	<0.001	0.77 (0.66 to 0.91)	0.001
	Year²	–	–	1.00 (1.00 to 1.00)	0.492	–	–	1.01 (1.00 to 1.02)	0.067
	Level	0.98 (0.90 to 1.07)	0.718	0.99 (0.90 to 1.08)	0.789	1.02 (0.84 to 1.22)	0.866	0.99 (0.82 to 1.19)	0.917
	Post-slope	0.93 (0.91 to 0.95)	<0.001	0.92 (0.88 to 0.95)	<0.001	1.01 (0.95 to 1.08)	0.720	0.92 (0.81 to 1.04)	0.180
13 year olds only (n=85 713; 18 721)	Year	0.90 (0.89 to 0.91)	<0.001	0.89 (0.86 to 0.92)	<0.001	0.90 (0.89 to 0.92)	<0.001	0.78 (0.65 to 0.94)	0.007
	Year²	–	–	1.00 (1.00 to 1.00)	0.459	–	–	1.01 (1.00 to 1.02)	0.107
	Level	0.95 (0.86 to 1.05)	0.321	0.95 (0.87 to 1.05)	0.349	1.22 (0.97 to 1.53)	0.086	1.19 (0.94 to 1.49)	0.145
	Post-slope	0.94 (0.92 to 0.97)	<0.001	0.93 (0.90 to 0.97)	<0.001	0.93 (0.85 to 1.01)	0.092	0.84 (0.73 to 0.98)	0.022
15 year olds only (n=79 486; 17 169)	Year	0.93 (0.92 to 0.94)	<0.001	0.86 (0.83 to 0.89)	<0.001	0.91 (0.90 to 0.93)	<0.001	0.70 (0.60 to 0.80)	<0.001
	Year²	–	–	1.00 (1.00 to 1.01)	<0.001	–	–	1.01 (1.01 to 1.02)	<0.001
	Level	1.09 (1.01 to 1.19)	0.034	1.13 (1.04 to 1.23)	0.006	1.11 (0.94 to 1.32)	0.218	1.06 (0.90 to 1.26)	0.473
	Post-slope	0.89 (0.87 to 0.91)	<0.001	0.83 (0.80 to 0.86)	<0.001	0.96 (0.90 to 1.02)	0.144	0.80 (0.71 to 0.89)	<0.001

*Available for England and Scotland only.
†Available for England only.