TABLE 2.
Associations between body mass index (BMI) and lung cancer by sex in the Japanese population (N = 444,143).
| Total | <18.5 | 18.5 to <21 | 21 to <23 | 23 to <25 | 25 to <30 | ≥30 | Heterogeneity for lowest category | Trend (per 5 kg/m2) | Heterogeneity for trend | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | I 2 (%) | Cochran's Q test | HR (95% CI) | p | I 2 (%) | Cochran's Q test | ||
| Both sexes | |||||||||||||
| Participants, n | 392,533 | 21,407 | 79,331 | 104,316 | 94,931 | 84,448 | 8100 | – | – | – | – | – | – |
| Person‐years | 5,733,351 | 254,390 | 1,104,802 | 1,527,754 | 1,430,791 | 1,292,930 | 122,685 | – | – | – | – | – | – |
| Cases, n | 6454 | 478 | 1464 | 1816 | 1469 | 1139 | 88 | – | – | – | – | – | – |
| HR1 (model 1) a | 1.43 (1.29–1.59) | 1.12 (1.04–1.21) | 1 (Ref.) | 0.85 (0.80–0.91) | 0.76 (0.71–0.83) | 0.73 (0.54–1.01) | 0.0 | p = 0.38 | 0.75 (0.71–0.79) | <0.0001 | 30.5 | p = 0.16 | |
| HR2 (model 2) b | 1.37 (1.23–1.52) | 1.11 (1.02–1.20) | 1 (Ref.) | 0.87 (0.81–0.93) | 0.77 (0.71–0.83) | 0.72 (0.52–1.00) | 0.0 | p = 0.31 | 0.77 (0.73–0.81) | <0.0001 | 32.2 | p = 0.15 | |
| HR3 (model 3) c | 1.35 (1.16–1.57) | 1.06 (0.98–1.14) | 1 (Ref.) | 0.87 (0.81–0.93) | 0.77 (0.71–0.84) | 0.69 (0.45–1.07) | 31.0 | p = 0.13 | 0.79 (0.75–0.83) | <0.0001 | 26.6 | p = 0.23 | |
| Men | |||||||||||||
| Participants, n | 180,495 | 8299 | 35,616 | 48,928 | 46,885 | 38,021 | 2746 | – | – | – | – | – | – |
| Person‐years | 2589,596 | 92,967 | 482,489 | 700,211 | 696,356 | 576,191 | 41,382 | – | – | – | – | – | – |
| Cases, n | 4727 | 336 | 1144 | 1371 | 1065 | 760 | 51 | – | – | – | – | – | – |
| HR1 (model 1) | 1.46 (1.28–1.66) | 1.16 (1.06–1.26) | 1 (Ref.) | 0.81 (0.75–0.89) | 0.73 (0.66–0.79) | 0.83 (0.61–1.14) | 3.0 | p = 0.26 | 0.71 (0.66–0.76) | <0.0001 | 36.1 | p = 0.11 | |
| HR2 (model 2) | 1.40 (1.23–1.60) | 1.14 (1.05–1.25) | 1 (Ref.) | 0.83 (0.77–0.91) | 0.74 (0.67–0.81) | 0.84 (0.61–1.15) | 7.6 | p = 0.18 | 0.73 (0.68–0.78) | <0.0001 | 34.1 | p = 0.11 | |
| HR3 (model 3) | 1.43 (1.19–1.71) | 1.10 (1.01–1.20) | 1 (Ref.) | 0.83 (0.75–0.91) | 0.74 (0.67–0.81) | 0.84 (0.57–1.25) | 34.4 | p = 0.11 | 0.74 (0.68–0.80) | <0.0001 | 45.8 | p = 0.07 | |
| Women | |||||||||||||
| Participants, n | 212,038 | 13,108 | 43,715 | 55,388 | 48,046 | 46,427 | 5354 | – | – | – | – | – | – |
| Person‐years | 3,143,755 | 161,423 | 622,312 | 827,542 | 734,435 | 716,739 | 81,303 | – | – | – | – | – | – |
| Cases, n | 1727 | 142 | 320 | 445 | 404 | 379 | 37 | – | – | – | – | – | – |
| HR1 (model 1) | 1.44 (1.17–1.76) | 0.98 (0.85–1.13) | 1 (Ref.) | 0.99 (0.86–1.13) | 0.93 (0.77–1.13) | 0.83 (0.55–1.24) | 0.0 | p = 0.32 | 0.86 (0.79–0.95) | 0.003 | 32.1 | p = 0.08 | |
| HR2 (model 2) | 1.34 (1.10–1.65) | 0.96 (0.83–1.11) | 1 (Ref.) | 1.00 (0.87–1.14) | 0.92 (0.76–1.11) | 0.78 (0.52–1.18) | 1.0 | p = 0.24 | 0.87 (0.79–0.96) | 0.0072 | 39.1 | p = 0.05 | |
| HR3 (model 3) | 1.20 (0.95–1.53) | 0.91 (0.78–1.07) | 1 (Ref.) | 0.99 (0.86–1.15) | 0.96 (0.76–1.22) | 0.71 (0.43–1.20) | 0.0 | p = 0.40 | 0.92 (0.84–1.01) | 0.0766 | 23.2 | p = 0.23 | |
Note: The interaction between smoking (never vs. ever) and BMI (<21 vs. ≥21) was not statistically significant (p = 0.07 for men and women combined, p = 0.09 for men, and p = 0.12 for women).
Abbreviations: CI, confidence interval; HR, hazard ratio; I 2, inconsistency index; p, probability; Ref. reference.
Adjustment for age (year, continuous) and area (for Japan Public Health Center–based prospective Study [JPHC]‐I, JPHC‐II, Japan Collaborative Cohort Study, and Life Span Study).
Further adjustment for smoking (men: never, former and current [pack years (PY) 0< and ≤20], former and current [PY 20< and ≤30], former and current [PY 30< and ≤40], former and current [PY >40]; women: never, former and current [PY 0< and ≤20], former and current [PY 20< and ≤30], former and current [PY >30]), drinking (noncurrent drinkers [never‐ or ex‐drinker], occasional drinkers [less than once per week], regular drinkers [<23 g/day], regular drinkers [≥23 g/day]) and history of diabetes (no, yes) to model 1.
Further adjustment for exercise to model 2.