Table 2. Incidence and hazard ratio of stroke by demographic factor and comorbidity among patients with head and neck cancers and reference cohort.

	Head and neck cancer
	No			Yes					Adjusteda
	Cases	Person-years	Rate	Cases	Person-years	Rate	Rate Ratio	(95% CI)	HR	(95% CI)
Overall	2915	369 020	7.90	694	60 983	11.4	1.44	(1.33–1.57)***	1.52	(1.40–1.65)***
Gender
Female	435	65 138	6.68	110	10 783	10.2	1.52	(1.07–1.62)*	1.53	(1.24–1.88)***
Male	2480	312 882	7.93	584	50 200	11.6	1.47	(1.34–1.61)***	1.57	(1.43–1.72)***
Age (years)
<40	57	65 882	0.87	57	12 085	4.72	5.45	(3.78–7.87)***	5.76	(3.99–8.33)***
40–49	392	124 335	3.15	146	20 644	7.07	2.24	(1.85–2.71)***	2.30	(1.90–2.78)***
50–59	689	94 618	7.28	203	15 433	13.2	1.81	(1.54–2.11)***	1.84	(1.57–2.15)***
⩾60	1777	84 185	21.1	288	12 821	22.5	1.06	(0.94–1.21)	1.06	(0.93–1.20)
Comorbidity
Hypertension	928	56 360	16.5	206	9959	20.7	1.26	(1.08–1.46)*	1.37	(1.18–1.59)***
Diabetes mellitus	752	44 543	16.9	148	7382	20.1	1.19	(1.00–1.42)	1.68	(1.52–1.84)***
Both	374	18 359	20.4	81	3239	25.0	1.23	(1.00–1.62)	1.32	(1.04–1.68)*
Follow-up (years)
<2	773	104 826	7.37	251	22 033	11.4	1.54	(1.36–1.78)***	1.64	(1.42–1.90)***
2–4	798	100 467	7.94	150	16 356	9.18	1.16	(0.97–1.38)	1.26	(1.05–1.50)*
5–6	795	96 087	8.27	164	13 847	11.8	1.43	(1.21–1.70)***	1.53	(1.29–1.81)***
7–8	495	60 391	8.20	118	7911	14.9	1.82	(1.49–2.23)***	1.97	(1.61–2.41)***
⩾8	54	7248	7.45	11	836	13.2	1.76	(0.92–3.37)	1.97	(1.03–3.78)***

Abbreviations: CI=confidence interval; HR=hazard ratio.

Rate: per 1000 person-years; Ratio: rate ratio of study cohort to reference cohort.

^*P<0.05, ^***P<0.0001.

^aAdjusted HR: multivariable analysis including gender, age, hypertension, diabetes mellitus, and years after index date.