Table 1.

Deaths among children with sickle cell disease, stratified by various baseline factors

	Deaths	Person-years of observation	Incidence per 1000 person-years of observation	IRR (95% CI)	p value	Adjusted IRR (95% CI)*	p value
Sickle cell disease clinic enrolment
No	18	172	104	1 (ref)	..	1 (ref)	..
Yes	8	273	29	0·28 (0·12–0·65)	0·0031	0·26 (0·11–0·62)	0·0024
Haemoglobin F
Below the median	18	213	85	1 (ref)	..	1 (ref)	..
Above the median	8	232	34	0·40 (0·17–0·92)	0·032	0·40 (0·17–0·94)	0·036
α+thalassaemia
Normal	13	186	70	1 (ref)	..	1 (ref)	..
Heterozygous	12	183	66	0·94 (0·43–2·07)	0·89	1·10 (0·46–2·25)	0·80
Homozygous	1	72	14	0·19 (0·02–1·51)	0·11	0·19 (0·02–1·49)	0·11
β-thalassaemia
Without β-thalassaemia	25	408	61	1 (ref)	..	1 (ref)	..
With β-thalassaemia	1	37	27	0·42 (0·05–3·15)	0·40	0·54 (0·06–4·36)	0·56

IRR=incidence rate ratio.

^*IRRs adjusted for α-thalassaemia genotype, and ethnic group, except for the α-thalassaemia analysis where adjustment was for ethnic group only.