Table 4.

All-cause mortality by age at cessation among all former smokers and former low-intensity smokers [≤10 cigarettes per day (CPD)] in the pooled analysis of nine cohort studies in the Japan Cohort Consortium

	Never smokers	Former smokers: age at cessation (years)					Current smokersa
		<30	30–39	40–49	50–59	≥60
All former smokers
Total, n	227 952	3947	10 112	14 352	12 525	8656	119 500
Death, n	40 266	503	1367	2952	4616	4964	34 429
HR (95% CI)b	1.00 (ref.)	1.04 (0.91–1.20)	0.96 (0.89–1.05)	1.08 (1.01–1.15)	1.29 (1.19–1.40)	1.37 (1.32–1.42)	1.62 (1.56–1.69)
I2c		41.30	33.82	41.17	77.87	0	69.94
Pd		0.02	0.08	0.04	<0.001	0.46	< 0.001
Former low-intensity smokers of ≤10 CPD
Total, n	227 952	1804	2564	3134	2702	2238	24 209
Death, n	40 266	215	409	629	938	1275	7701
HR (95% CI)	1.00 (ref)	0.93 (0.77–1.13)	1.05 (0.90–1.22)	1.04 (0.93–1.16)	1.22 (1.14–1.31)	1.37 (1.28–1.47)	1.58 (1.52–1.63)
I2		31.75	46.04	37.84	0	18.95	26.77
P		0.08	0.02	0.05	0.56	0.4	0.14

^aCurrent low-intensity smokers who smoked ≤10 CPD for the analysis of former low-intensity smokers.

^bAdjusted for age, alcohol intake (men: never, former, <1 time/week, regularly <23, 23 to <46, ≥46 g/d; women: never, former, <1 time/week, regularly <23, ≥23 g/d) and region (for the Japan Public Health Center-based Prospective Study, Cohort I, the Japan Public Health Center-based Prospective Study, Cohort II, the Japan Collaborative Cohort Study and the Life Span Study).

^c I ² statistics describe the percentage of variation across studies due to heterogeneity rather than chance.

^dCochrane’s Q statistics for a homogeneity test.