Table 6. Causal effects from number unit increase of age at first birth to common lung cancer risk factors.

Outcomes	Causal effect (95% CI)	P value
Former vs. current smoker	1.01 (0.99–1. 03)	0.310
Ever vs. never smoked	1.10 (0.92–1.30)	0.292
Age of smoking initiation	0.94 (0.81–1.10)	0.463
Cigarettes smoked per day	0.52 (0.24–1.12)	0.094
Body mass index	0.93 (0.88–0.98)	0.004
Triglycerides	0.95 (0.91–1.00)	0.051
Total cholesterol	1.01 (0.95–1.08)	0.666
Alcohol drinker status: previous	0.99 (0.99–1.00)	0.004
Alcohol drinker status: never	1.00 (1.00–1.01)	0.368
Years of schooling	1.12 (1.08,1.16)	<0.001
Waist-to-hip ratio	0.97 (0.90,1.03)	0.318
Type 2 diabetes	0.89 (0.74,1.06)	0.187