Table 2– Incidence rates and hazard ratios (HRs) for hospitalisation with pneumonia among males and females according to body mass index

	Body mass index kg·m⁻²
	<22.5	22.5–24.9	25.0–29.9	30.0–34.9	≥35
Males
Incidence rate per 1,000 person-yrs	5.2	3.6	3.9	5.4	7.0
Overall HR (95% CI)
Crude^#	1.5 (1.2–1.8)	1.0 (ref.)	1.1 (0.9–1.2)	1.5 (1.2–1.8)	2.1 (1.5–3.0)
Adjusted^¶	1.4 (1.1–1.7)	1.0 (ref.)	1.1 (0.9–1.3)	1.4 (1.2–1.7)	2.0 (1.4–2.8)
Adjusted⁺	1.4 (1.1–1.7)	1.0 (ref.)	1.0 (0.8–1.1)	1.0 (0.8–1.3)	1.2 (0.8–1.7)
HR (95% CI) by subgroup^¶
Age yrs
50–54	1.3 (0.8–1.9)	1.0 (ref.)	1.0 (0.8–1.4)	1.6 (1.1–2.3)	1.4 (0.7–2.9)
55–59	1.2 (0.8–1.7)	1.0 (ref.)	0.8 (0.6–1.1)	1.2 (0.9–1.7)	2.0 (1.2–3.5)
≥60	1.7 (1.2–2.4)	1.0 (ref.)	1.4 (1.1–1.7)	1.5 (1.1–2.1)	2.3 (1.3–4.3)
Smoking status^§
Nonsmokers	1.0 (0.6–1.4)	1.0 (ref.)	1.1 (0.9–1.4)	1.6 (1.2–2.2)	2.6 (1.6–4.1)
Current smokers	1.6 (1.2–2.1)	1.0 (ref.)	1.1 (0.9–1.3)	1.3 (1.0–1.7)	1.3 (0.7–2.4)
Females
Incidence rate per 1,000 person-yrs	4.0	3.4	3.0	2.9	4.3
Overall HR (95% CI)
Crude^#	1.3 (1.1–1.5)	1.0 (ref.)	0.8 (0.7–1.0)	0.8 (0.6–1.0)	1.2 (0.8–1.6)
Adjusted^¶	1.2 (1.0–1.4)	1.0 (ref.)	0.9 (0.7–1.0)	0.8 (0.6–1.0)	1.2 (0.8–1.6)
Adjusted⁺	1.2 (1.0–1.4)	1.0 (ref.)	0.8 (0.7–1.0)	0.7 (0.6–0.9)	0.8 (0.6–1.1)
HR (95% CI) by subgroup^¶
Age yrs
50–54	1.3 (0.9–1.8)	1.0 (ref.)	0.8 (0.6–1.2)	0.9 (0.6–1.5)	1.1 (0.5–2.4)
55–59	1.2 (0.9–1.6)	1.0 (ref.)	0.9 (0.7–1.2)	0.8 (0.5–1.2)	1.3 (0.8–2.4)
≥60	1.2 (0.9–1.5)	1.0 (ref.)	0.8 (0.7–1.1)	0.8 (0.6–1.2)	1.1 (0.7–1.8)
Smoking status^§
Nonsmokers	1.0 (0.8–1.3)	1.0 (ref.)	0.8 (0.6–1.0)	0.7 (0.5–1.0)	1.4 (0.9–2.0)
Current smokers	1.3 (1.1–1.7)	1.0 (ref.)	1.0 (0.8–1.2)	1.1 (0.8–1.5)	1.0 (0.5–1.7)

^#: the crude HR was calculated with the use of Cox's regression, with age as the underlying time variable; ^¶: multivariable-adjusted model was based on the crude model with additional adjustment for smoking status, alcohol intake, schooling and educational level; ⁺: multivariable-adjusted model as specified above and with additional adjustment for other major chronic diseases diagnosed during follow-up; ^§: HRs in strata of smoking status were not adjusted for smoking status.