Plasmodium falciparum infection and disease in infancy associated with increased risk of malaria and anaemia in childhood

Table 2 Incidence rate ratio of any malaria and clinical malaria between 6 and 24 months and mean cumulative episodes of malaria at follow-up timepoints by cohort

	N = 437	Follow-up (person years)	Any malaria infections				Clinical malaria
	N = 437	Follow-up (person years)	Cases	Incidence PPY^a	Unadjusted IRR (95% CI)	P-value^b	Cases	Incidence PPY^a	Unadjusted IRR (95% CI)	P-value^b
Any malaria (first 6 months)
No	310	279.1	439	1.57	REF	< .0001	210	0.75	REF	< 0.0001
Yes	127	114.6	303	2.64	1.68 (1.45–1.95)		161	1.40	1.87 (1.52–2.29)
Asympomatic. Pf infection (first 6 months)^c
No	289	259.8	381	1.47	REF	0.0009	179	0.69	REF	0.06
Yes	99	81.9	164	2.00	1.37 (1.14–1.64)		73	0.89	1.29 (0.98–1.70)
Clinical malaria (first 6 months)
No	388	341.7	545	1.59	REF	< .0001	252	0.74	REF	< 0.0001
Yes	49	52.0	197	3.79	2.37 (2.02–2.80)		119	2.29	3.10 (2.49–3.87)
Infant sex
Female	238	209.4	389	1.86	REF	0.76	186	0.89	REF	0.21
Male	195	182.0	346	1.90	1.02 (0.88–1.18)		184	1.01	1.14 (0.93–1.40)
Study site
Liwonde	344	260.7	258	0.99	REF	< .0001	76	0.29	REF	< 0.0001
Mfera	93	133.0	484	3.64	3.68 (3.16–4.28)		295	2.22	7.61 (5.91–9.79)
Season of birth
Dry	146	262.4	529	2.02	REF	0.007	279	1.06	REF	0.0005
Rainy	291	131.3	213	1.62	0.80 (0.69–0.94)		92	0.70	0.66 (0.52–0.83)
% follow-up time in rainy season
Each unit increase	437	393.7	742	1.88	0.95 (0.94- 0.96)	< .0001	371		0.94 (0.93–0.94)	< 0.0001
Maternal age
Each year increase	437	393.7	742	1.88	0.98 (0.97–0.99)	0.001	371	0.94	0.97(0.95–0.98)	0.0002
Gravidity
Each unit increase	437	393.7	742	1.88	1.05 (1.01–1.09)	0.01	371	0.94	1.04 (0.98–1.09)	0.21

^aPer person-year; ^bChi-square; ^cSample restricted to participants who did not experience clinical malaria during first 6 months

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