Table 2 Cox model HR and 95% CI for lung cancer mortality in lifetime smoky coal users in Xuanwei, China, 1976–1996a

From: Portable stove use is associated with lower lung cancer mortality risk in lifetime smoky coal users

 

Men and women

Men

Women

 

HR (95% CI)

P -value

HR (95% CI)

P -value

HR (95% CI)

P -value

No stove change

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Stove change

0.52 (0.41–0.64)

<0.0001

0.62 (0.46–0.82)

0.001

0.41 (0.29–0.57)

<0.0001

Used annual average <2 tons of smoky coal

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Used annual average ⩾2 to <3 tons of fuel

1.61 (1.27–2.03)

<0.0001

1.27 (0.93–1.73)

0.133

2.07 (1.43–3.00)

0.0001

Used annual average ⩾3 to <4 tons of fuel

2.19 (1.73–2.79)

<0.0001

1.77 (1.29–2.43)

0.0004

2.70 (1.85–3.93)

<0.0001

Used annual average ⩾4 tons of fuel

2.37 (1.84–3.06)

<0.0001

1.69 (1.21–2.38)

0.002

3.32 (2.24–4.92)

<0.0001

No lung cancer in spouse

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Lung cancer in spouse

1.77 (1.43–2.18)

<0.0001

1.47 (1.07–2.02)

0.019

2.12 (1.60–2.82)

<0.0001

No lung cancer in parents, siblings, and children

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Lung cancer in parents, siblings, and children

1.36 (1.08–1.70)

0.008

1.48 (1.10–1.99)

0.010

1.20 (0.85–1.69)

0.311

No history of COPD

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

History of COPD

1.24 (1.08–1.43)

0.003

1.33 (1.10–1.62)

0.004

1.19 (0.97–1.46)

0.103

No history of tuberculosis

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

History of tuberculosis

1.38 (0.80–2.39)

0.252

1.95 (0.96–3.95)

0.065

0.89 (0.37–2.15)

0.789

<7 waking hours indoors per day, until 20 years old

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

⩾7 waking hours indoors per day, until 20 years old

1.11 (0.98–1.26)

0.089

1.03 (0.86–1.23)

0.747

1.21 (1.02–1.45)

0.034

Average of <2 rooms in all houses throughout life

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Average of ⩾2 rooms in all houses throughout life

1.10 (0.97–1.25)

0.155

1.18 (0.98–1.42)

0.075

1.03 (0.85–1.24)

0.755

Illiterate

1.00 (reference)

 

1.00 (reference)

 

1.00 (reference)

 

Literate

1.19 (1.02–1.38)

0.023

1.15 (0.95–1.39)

0.146

1.27 (0.97–1.65)

0.082

Never coal miner

1.00 (reference)

 

1.00 (reference)

 

Not applicable

 

Ever coal miner

3.34 (2.56–4.36)

<0.0001

3.39 (2.57–4.47)

<0.0001

Not applicable

 

<20 years of smoking

1.00 (reference)

 

1.00 (reference)

 

Not applicable

 

⩾20 years of pipe smoking

0.86 (0.69–1.08)

0.197

0.84 (0.64–1.11)

0.223

Not applicable

 

20–40 years of cigarette smoking

1.21 (0.96–1.53)

0.114

1.22 (0.91–1.63)

0.179

Not applicable

 

⩾40 years of cigarette smoking

1.42 (1.04–1.94)

0.027

1.44 (0.99–2.09)

0.054

Not applicable

 

Never cooked

Not applicable

1.00 (reference)

 

Not applicable

 

Ever cooked

Not applicable

0.94 (0.73–1.22)

0.650

Not applicable

 

<20 years of cooking

1.00 (reference)

 

Not applicable

1.00 (reference)

 

20–40 years of cooking

1.27 (1.03–1.55)

0.023

Not applicable

1.45 (0.91–2.32)

0.121

⩾40 years of cooking

1.44 (1.12–1.86)

0.004

Not applicable

1.53 (0.92–2.54)

0.103

  1. CIs=confidence intervals; HRs=hazard ratios.
  2. aCox models include the time-dependent variables for change to portable stove, average tons of fuel used annually (2–<3 tons, 3–<4 tons, ⩾4 tons, compared with <2 tons), years of smoking (20–40 years, ⩾40 years, compared with <20 years), and years of cooking (20–40 years, ⩾40 years, compared with <20 years), along with dummy variables for history of spousal lung cancer (yes vs no), family history of lung cancer (parents, siblings, or children) (yes vs no), history of chronic bronchitis (yes vs no), history of tuberculosis (yes vs no), number of hours spent indoors until the age of 20 years (<7 vs ⩾7 h), average number of rooms in all households throughout life (<2 rooms vs ⩾2 rooms), educational status (illiterate vs literate), and history of working as a miner (yes vs no). Sex-specific Cox-regression models include the same covariates, as well as, history of ever cooking (ever vs never) in men. Birth cohort effects are controlled by stratification within the model by 5-year intervals (born during 1917–1921, 1922–1926, 1927–1931, 1932–1936, 1937–1941, 1942–1946, and 1947–1951).
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