Table 2.

Results from random-effects meta-analytic models on data from 18 cohorts.

model		summary SMD		heterogeneity statistics					forest plot
		estimatea [95% CI]	p-value	Q17	p-value	τ2	I2 (%)	H2
1	difference in LTL between time-points	−0.49 [−0.62, −0.36]	<0.0001	333.73	<0.0001	0.07	95.89	24.31	electronic supplementary material, figure S2a
2	assn. between smoking and baseline LTL	−0.10 [−0.16, −0.05]	0.0003	26.55	0.0650	0.01	44.70	1.81	figure 2a
3	assn. between smoking and follow-up LTL	−0.15 [−0.29, −0.01]	0.0312	95.13	<0.0001	0.06	89.78	9.78	figure 2b
4	difference in assn. between smoking and LTL between time-points	−0.05 [−0.16, 0.06]	0.3884	73.45	<0.0001	0.04	90.41	10.43	figure 3a
5	combined assn. between smoking and LTL across time-points	−0.13 [−0.22, −0.03]	0.0075	85.62	<0.0001	0.03	83.96	6.24	not shown
6	assn. between smoking and LTL attrition	−0.02 [−0.07, 0.04]	0.5311	24.68	0.1021	0.00	36.48	1.57	figure 4a

^aNegative parameter estimates for the summary standardized mean difference (SMD) correspond to: model 1—shorter LTL at follow-up; models 2, 3 and 5—shorter LTL in smokers; model 4—stronger assn. between smoking and LTL at follow-up; model 6—faster attrition in smokers. Significant associations are shown in italics.