Table 4 Standardised incidence ratios (SIRs) and their 95% confidence intervals (CIs) for anal cancer among patients with anal fissure, fistula, or perianal abscess*.

	Fissure			Fistula			Perianal abscess
	Obs	SIR	95% CI	Obs	SIR	95% CI	Obs	SIR	95% CI
Overall	5	3.9	1.3–9.2	2	1.3	0.2–4.9	6	5.3	1.9–11.5
Sex
Men	2	4.7	0.6–16.9	1	1.3	0.03–7.4	1	1.6	0.04–9.0
Women	3	3.6	0.7–10.4	1	1.4	0.04–7.6	5	9.7	3.1–22.6
Follow up duration (y)
3–9	3	5.9	1.2–17.3	0	–	–	4	7.1	1.9–18.3
10+	2	2.6	0.3–9.4	2	2.1	0.3–7.5	2	3.5	0.4–12.5

*Person years and anal cancer cases accrued during the first three years of follow‐up were excluded.

Obs, observed.