Table 2.

Logistic regression predicting ‘good’ knowledge (1996–2008)

Predictor variables	n	Good knowledge (%)	Univariate		Multivariate
			OR	95% CI	OR	95% CI
Gender
Female	16 721	59	1.00		1.00
Male	13 641	56	0.87	0.83–0.92	0.90	0.86–0.95
Age (years)
45–64	9721	57	1.00		1.00
16–24	1936	57	1.03	0.94–1.13	1.05	0.94–1.18
25–44	11 035	62	1.27	1.20–1.35	1.20	1.12–1.29
65+	7670	52	0.82	0.77–0.88	0.77	0.72–0.83
Social class
Skilled manual and non-manual	13 237	57	1.00		1.00
Managerial and professional	10 583	61	1.21	1.15–1.28	1.09	1.03–1.16
Part skilled and unskilled	6542	53	0.86	0.80–0.92	0.93	0.87–1.00
Number of cars
1	13 754	57	1.00
0	7117	52	0.80	0.75–0.85	0.96	0.89–1.03
2+	9491	61	1.17	1.12–1.24	1.03	0.96–1.09
Smoking status
Never	13 937	65	1.00		1.00
Ex	8811	59	0.79	0.75–0.84	0.86	0.81–0.92
Light	5375	46	0.46	0.43–0.49	0.45	0.42–0.48
Heavy	2239	34	0.28	0.25–0.31	0.28	0.25–0.31
Adults in household
2	16 323	59	1.00		1.00
1	9804	54	0.80	0.76–0.84	0.96	0.91–1.03
3+	4235	57	0.90	0.84–0.96	0.89	0.83–0.96
Child in the household
No child <16	21 930	55	1.00		1.00
<16 years	8432	63	1.39	1.32–1.47	1.24	1.16–1.33
Year
2003–06	9392	56	1.00		1.00
1996–2002	17 510	60	0.83	0.79–0.88	0.85	0.80–0.90
2007–08a	3460	59	0.95	0.88–1.03	0.92	0.84–1.01

For every consecutive increase in the predictor variable ‘year’, the OR represents the increase in odds of the outcome occurring. For all categorical variables, the OR describes a multiplicative change in the outcome compared with the reference category.

^aThe 2008 data were collected in February and March 2009 due to a sampling error in October and November 2008.