Efficacy of prophylactic intermittent zinc supplementation for reducing acute respiratory infections and diarrhoea in infants: A randomized controlled trial

Table 1 Baseline characteristics of the study participants, n (%)

Characteristic	Intervention group (Zinc group), n = 160	Control group, n = 160	P value
Mean age, month; mean ± SD	2.2 (0.7)	2.3 (0.6)	0.40
Weight, gram; mean ± SD	4140 (136)	4137 (122)	0.83
Length, cm; mean ± SD	56.3 (1.7)	56.5 (1.1)	0.08
Male:Female ratio	0.75	0.74	0.97
Lower & upper lower SES	78/160 (49)	82/160 (51)	0.66
Lower middle, upper middle & upper SES	82/160 (51)	78/160 (49)	0.66
Exclusive breast feeding	114/160 (71)	119/160 (74)	0.53
Maternal education level			0.41
None or below primary	115/160 (72)	109/160 (68)
Primary	36/160 (22)	39/160 (24)
Secondary or above	9/160 (6)	12/160 (8)

SES: Socioeconomic status.

Table 2 Effect of zinc supplementation on the incidence of acute respiratory infections, diarrhoea and growth in the study participants (Intention to treat analysis)

Outcome	Intervention group (Zinc group), n = 160	Control group, n = 160	Mean difference (95%CI)	P value	Effect size (Cohen’s d value)
Estimated total annual episodes of ARI per group	40	147	----	----	----
Estimated mean annual incidence of ARI (episodes/child-year); mean ± SD	0.25 (0.61)	0.92 (1.22)	-0.67 (-0.88 to -0.45)	< 0.001	-0.69
Estimated total annual episodes of diarrhoea per group	166	331	----	----	----
Estimated mean annual incidence of acute diarrhoea (episodes/child-year); mean ± SD	1.04 (1.30)	2.07 (2.09)	-1.03 (-1.42 to -0.65)	< 0.001	-0.59
Estimated mean annual duration of diarrhoea (days/child-year)	3.10 (3.82)	7.64 (7.67)	-4.54 (-5.87 to -3.20)	< 0.001	-0.75
Gain in weight over 6 months (gram)	3150 (108)	2818 (76)	332 (310 to 352)	< 0.001	3.56
Gain in length over 6 months (cm)	10 (0.6)	8.6 (0.4)	1.4 (1.3 to 1.5)	< 0.001	2.74
Estimated mean annual incidence of mild ARI	0.11 (0.27)	0.52 (0.68)	RR = 0.21 (0.1 to 0.32), RRR = 79% (68 to 90)	P = 0.037	0.69
Estimated mean annual incidence of moderate to severe ARI	0.14 (0.35)	0.40 (0.53)	RR = 0.35 (-0.13 to 0.85), RRR = 65% (15 to 113)	P = 0.64	0.35
Estimated mean annual incidence of mild diarrhoea	0.63 (0.78)	0.95 (0.96)	RR = 0.66 (0. 56 to 0.76), RRR = 34% (24 to 44)	P = 0.006	0.61
Estimated mean annual incidence of moderate to severe diarrhoea	0.41 (0.53)	1.12 (1.13)	RR = 0.37 (0.28 to 0.46), RRR = 63% (54 to 72)	P = 0.002	1.07

ARI: Acute respiratory infections; RR: Relative risk/Risk ratio; RRR: Relative risk reduction. Diarrhoea severity was assessed using the Modified Vesikari Score. For the purpose of this study, ARI severity was classified based on the level of medical intervention required: Mild (outpatient treatment), moderate (oxygen supplementation or ward admission), and severe (paediatric intensive care unit admission or ventilator support).