Body mass index and incidence of lung cancer in the HUNT study: using observational and Mendelian randomization approaches

Table 2 The association of BMI in HUNT2 with incidence of lung cancer overall and different histologic types, the HUNT Study, 1995–97 to 2017 (N = 62,453)

LC	BMI (kg/m²)	Cases	IR (per 1000 person-years)	Crude model^a		Main model^b		Additional Model^c		Main Model after imputation^d
				HR	95% CI	HR	95% CI	HR	95% CI	HR	95% CI
Overall	< 25.0	435	0.90	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	25.0–29.9	426	0.84	0.65	0.57–0.74	0.79	0.69–0.91	0.79	0.69–0.91	0.80	0.70–0.92
	≥ 30.0	148	0.80	0.54	0.45–0.66	0.75	0.62–0.91	0.75	0.62–0.91	0.77	0.64–0.93
SC	< 25.0	62	0.13	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	25.0–29.9	66	0.13	0.71	0.50–1.00	0.97	0.68–1.38	0.96	0.68–1.36	0.98	0.69–1.39
	≥ 30.0	29	0.16	0.75	0.48–1.17	1.13	0.72–1.77	1.11	0.71–1.74	1.15	0.73–1.80
AD	< 25.0	150	0.31	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	25.0–29.9	139	0.27	0.63	0.50–0.79	0.73	0.58–0.92	0.73	0.58–0.92	0.73	0.58–0.93
	≥ 30.0	38	0.20	0.42	0.29–0.60	0.53	0.37–0.76	0.53	0.37–0.76	0.53	0.37–0.76
SQ	< 25.0	83	0.17	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	25.0–29.9	86	0.17	0.67	0.50–0.91	0.81	0.60–1.10	0.81	0.60–1.11	0.82	0.61–1.12
	≥ 30.0	30	0.16	0.56	0.37–0.85	0.84	0.55–1.28	0.83	0.54–1.27	0.88	0.57–1.34

Tvc option of the stcox command in Stata was used to model the non-proportional hazards in the main, additional, and imputed models. Non-proportional hazards for LC overall: sex, smoking and economic difficulties; for SC: smoking, family history of cancer, economic difficulties, and leisure physical activity; for AD: sex, smoking, economic difficulties and leisure physical activity; for SQ: education
Abbreviations: AD adenocarcinoma, CI confidence interval, HR hazard ratio, HUNT The Trøndelag Health Study, IR incidence rate, LC lung cancer, SC small cell lung cancer, SQ squamous cell lung cancer
^aAge was used as the time scale in the crude model
^bMain model adjusted for sex, smoking, passive smoking, leisure physical activity, total sitting time daily, education, economic difficulties, family history of cancer, and self-reported chronic obstructive pulmonary disease (COPD). Age was used as the time scale
^cAdjusted for covariables in the main model plus asthma, alcohol consumption, and occupational activity. Age was used as the time scale
^dMissing information in the covariates of the main model were imputed

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