Cooking fuel and risk of under-five mortality in 23 Sub-Saharan African countries: a population-based study

Figures & data

Table 1. Characteristics of children five and under in Sub-Saharan Africa, by cooking fuel (n = 783,691).

			Cooking fuel type
		Clean n (%wt)^a	Charcoal n (%wt)^a	Biomass n (%wt)^a	Other n (%wt)^a	p-value
Total number		32,037 (4.7)	111,885 (14.6)	612,569 (76.7)	27,200 (4.0)
Kitchen location
Separate building		3,280 (1.0)	30,494 (9.0)	264,987 (88.0)	6,104 (2.0)	< 0.001
In the house		26,405 (14.3)	26,399 (12.8)	141,105 (66.4)	11,373 (6.6)
Outdoors		2,352 (1.0)	54,992 (22.1)	206,477 (72.7)	9,723 (4.2)
Country, year
Bukina Faso, 2010		656 (1.6)	1,369 (2.5)	51,257 (96.0)	8 (0.0)	< 0.001
Benin, 2011/12		874 (2.8)	6,879 (19.6)	34,599 (76.6)	361 (1.0)
Burundi, 2010		17 (0.0)	2,790 (6.7)	20,377 (93.3)	0 (0.0)
DRC, 2013/2014		619 (1.3)	11,555 (24.7)	44,107 (73.9)	84 (0.2)
Congo, 2011/12		1,550 (12.7)	5,394 (33.9)	20,451 (46.5)	927 (6.9)
Côte d’Ivoire, 2011/12		1,672 (10.8)	3,404 (14.3)	20,153 (74.8)	52 (0.2)
Ethiopia, 2011		337 (0.5)	2,940 (3.9)	38,810 (94.9)	750 (0.6)
Gabon, 2012		11,550 (84.4)	496 (1.4)	5,731 (13.6)	77 (0.6)
Gambia, 2013		65 (0.3)	3,601 (17.9)	20,153 (81.7)	18 (0.0)
Guinea, 2012		34 (0.1)	5,243 (22.4)	20,554 (77.4)	16 (0.1)
Kenya, 2014		1,113 (5.5)	5,726 (16.0)	29,282 (72.9)	823 (5.7)
Comoros, 2012		235 (2.4)	170 (1.3)	8,016 (84.0)	1,425 (12.3)
Liberia, 2013		9 (0.1)	3,694 (27.6)	20,712 (72.4)	1 (0.0)
Mali, 2012/13		83 (0.3)	3,186 (10.1)	24,684 (89.4)	110 (0.3)
Mozambique, 2011		1,185 (2.1)	5,369 (12.8)	27,586 (84.1)	477 (1.0)
Nigeria, 2013		1,509 (1.3)	2,952 (2.8)	94,299 (81.1)	15,294 (14.9)
Namibia, 2013		3,654 (43.4)	49 (0.4)	5,463 (54.2)	93 (2.1)
Rwanda, 2010		3 (0.0)	2,603 (7.2)	27,988 (92.8)	1 (0.0)
Sierra Leone, 2013		15 (0.0)	5,967 (13.5)	37,347 (86.5)	28 (0.0)
Togo, 2013/14		584 (2.9)	17,793 (64.5)	324 (1.4)	6,380 (31.2)
Uganda, 2011		109 (0.3)	5,578 (17.2)	22,001 (82.4)	39 (0.1)
Zambia, 2013/14		2,390 (6.9)	15,103 (33.8)	25,489 (59.3)	30 (0.0)
Zimbabwe, 2010/11		3,774 (21.7)	24 (0.1)	13,186 (76.6)	206 (1.6)
Residence
Urban		27,008 (15.0)	73,315 (34.2)	100,245 (39.3)	21,457 (11.6)	< 0.001
Rural		5,029 (0.6)	38,570 (6.6)	512,324 (91.9)	5,743 (0.9)
Sex
Male		16,200 (4.7)	56,615 (14.5)	312,434 (76.8)	13,771 (4.0)	0.042
Female		15,837 (4.8)	55,270 (14.7)	300,135 (76.4)	13,429 (4.1)
Breastfeeding status
No		26,081 (6.2)	75,853 (15.8)	372,675 (73.3)	20,064 (4.7)	< 0.001
Yes		5,956 (2.4)	36,032 (12.6)	239,894 (82.2)	7,136 (2.8)
No. of under-5 in HH, mean (SD)^b		1.2 (1.1)	1.5 (1.2)	1.7 (1.4)	1.2 (1.1)	< 0.001
Mother’s age, mean (SD)^b		35.7 (7.7)	34.9 (7.7)	35.6 (7.9)	35.2 (7.6)	< 0.001
Family size, mean (SD)^b		6.1 (3.1)	7.0 (3.7)	7.5 (4.1)	5.7 (3.0)	< 0.001
Member smoking in HH
No		26,132 (5.0)	89,603 (15.2)	466,620 (75.1)	24,087 (4.6)	< 0.001
Yes		5,905 (3.8)	22,282 (12.4)	145,949 (81.8)	3,113 (2.0)
Wealth index
Poorest		2,158 (0.6)	10,970 (4.4)	189,324 (94.9)	322 (0.1)	< 0.001
Poorer		3,686 (1.7)	11,935 (6.6)	156,423 (91.4)	568 (0.3)
Middle		2,929 (2.4)	15,509 (10.0)	136,339 (86.0)	2,328 (1.6)
Richer		5,798 (5.1)	27,779 (21.2)	97,537 (66.5)	8,826 (7.2)
Richest		17,466 (18.2)	45,692 (39.7)	32,946 (27.4)	15,156 (14.7)
Mother’s education
No education		2,065 (0.7)	37,872 (9.2)	355,694 (88.9)	4,387 (1.2)	< 0.001
Primary		8,219 (3.5)	39,221 (16.2)	188,936 (76.4)	7,876 (3.9)
Secondary		17,426 (16.3)	31,018 (27.4)	63,700 (45.0)	12,023 (11.3)
Higher		4,327 (33.5)	3,774 (24.3)	4,239 (23.6)	2,914 (18.6)
Mother’s occupation
Not employed		10,645 (5.8)	28,033 (15.2)	154,171 (76.1)	5,010 (2.9)	< 0.001
Professional/office-related		5,600 (28.5)	5,943 (24.6)	9,218 (35.6)	2,653 (11.3)
Sales		8,435 (6.0)	38,086 (23.3)	106,217 (61.6)	13,039 (9.0)
Farming		1,480 (0.3)	21,069 (6.4)	281,392 (92.9)	1,077 (0.3)
Other services		5,877 (8.3)	18,754 (20.9)	61,571 (63.6)	5,421 (7.2)
Father’s occupation
Not employed		702 (1.1)	10,389 (13.9)	55,254 (83.9)	718 (1.1)	< 0.001
Professional/office-related		10,194 (16.0)	16,714 (23.8)	43,361 (52.2)	5,352 (8.1)
Sales		3,202 (5.7)	13,999 (22.0)	44,641 (64.6)	4,661 (7.7)
Farming		1,709 (0.3)	28,751 (6.7)	352,940 (92.5)	2,341 (0.5)
Other services		16,230 (10.1)	42,032 (24.2)	116,373 (56.7)	14,128 (9.0)
Under-5 mortality
Alive		30,215 (5.1)	100,502 (15.1)	529,813 (75.6)	25,000 (4.2)	< 0.001
Dead		1,822 (2.1)	11,383 (11.6)	82,756 (83.8)	2,200 (2.5)

^a n is unweighted number, while the row percentages (%_wt) were weighted using a Taylor series linearization by incorporating the primary sampling unit, sampling strata (cluster), country, and sampling weights.

^b Linear regression was used for continuous variables; HH, household.

Figure 1. (Color online) The geographical distribution of solid cooking fuel usage by place of residence, (A) urban and (B) rural.

Table 2. Cox proportional hazard ratios (HRs) for the risk of under-five mortality resulting from cooking fuel (n = 783,691).

	Model 1	Model 2
	Crude HR (95 % CI)	Adjusted HR (95 % CI)^a
Cooking fuel (Ref: Clean)
Charcoal	1.97 (1.80, 2.16)***	1.21 (1.10, 1.34)***
Biomass	2.67 (2.46, 2.90)***	1.20 (1.08, 1.32)***
Other	1.49 (1.34, 1.66)***	1.01 (0.90, 1.14)
Kitchen location (Ref: Separate building)
In the house	1.10 (1.06, 1.14)***	1.06 (1.03, 1.10)***
Outdoors	1.08 (1.05, 1.11)***	0.98 (0.95, 1.01)
Country (Ref: Benin)
Bukina Faso, 2010	1.92 (1.79, 2.05)***	1.96 (1.83, 2.09)***
Burundi, 2010	1.85 (1.71, 2.00)***	1.92 (1.77, 2.08)***
DRC, 2013/14	1.65 (1.52, 1.80)***	1.78 (1.64, 1.93)***
Congo, 2011/12	1.08 (0.98, 1.18)	1.25 (1.13, 1.37)***
Côte d’Ivoire, 2011/12	1.33 (1.21, 1.46)***	1.45 (1.33, 1.58)***
Ethiopia, 2011	1.48 (1.37, 1.61)***	1.48 (1.37, 1.61)***
Gabon, 2012	0.64 (0.57, 0.73)***	0.95 (0.83, 1.09)
Gambia, 2013	0.82 (0.73, 0.92)***	0.94 (0.83, 1.06)
Guinea, 2012	1.69 (1.56, 1.84)***	1.68 (1.55, 1.82)***
Kenya, 2014	0.84 (0.76, 0.91)***	0.94 (0.86, 1.03)
Comoros, 2012	0.52 (0.42, 0.63)***	0.62 (0.51, 0.75)***
Liberia, 2013	1.87 (1.72, 2.03)***	2.15 (1.98, 2.34)
Mali, 2012/13	1.36 (1.24, 1.49)***	1.31 (1.14, 1.51)***
Mozambique, 2011	1.74 (1.61, 1.89)***	1.81 (1.67, 1.96)***
Nigeria, 2013	1.83 (1.70, 1.97)***	1.97 (1.84, 2.12)***
Namibia, 2013	0.69 (0.60, 0.79)***	0.93 (0.81, 1.06)
Rwanda, 2010	1.67 (1.55, 1.80)***	1.97 (1.82, 2.12)***
Sierra Leone, 2013	2.59 (2.40, 2.79)***	2.73 (2.54, 2.95)***
Togo, 2013/14	1.19 (1.08, 1.29)***	1.38 (1.26, 1.52)***
Uganda, 2011	1.58 (1.45, 1.72)***	1.73 (1.51, 1.97)***
Zambia, 2013/14	1.37 (1.27, 1.48)***	1.57 (1.45, 1.70)***
Zimbabwe, 2010/11	0.78 (0.71, 0.87)***	0.91 (0.82, 1.02)
Residence (Ref: Urban)	1.54 (1.49, 1.60)***	1.08 (1.04, 1.12)***
Child’s sex (Ref: Male)	0.94 (0.92, 0.95)***	0.94 (0.93, 0.96)***
Breastfeeding status (Ref: No)	1.49 (1.46, 1.52)***	1.03 (1.01, 1.06)**
No. of under-5 in HH (in 1 unit increment)	1.08 (1.07, 1.09)***	1.05 (1.03, 1.06)***
Mother’s age (in 1 year increment)	0.95 (0.95, 0.95)***	0.95 (0.95, 0.96)***
Family size (in 1 unit increment)	0.98 (0.98, 0.99)***	0.97 (0.97, 0.98)***
Member smoking in HH (Ref: No)	1.18 (1.15, 1.22)***	1.09 (1.06, 1.12)***
Wealth index (Ref: poorest)
Poorer	0.92 (0.89, 0.95)***	0.95 (0.92, 0.98)***
Middle	0.79 (0.76, 0.82)***	0.87 (0.84, 0.90)***
Richer	0.68 (0.66, 0.71)***	0.80 (0.77, 0.83)***
Richest	0.47 (0.45, 0.50)***	0.65 (0.61, 0.69)***
Mother’s education (Ref: No education)
Primary	0.82 (0.80, 0.84)***	0.91 (0.89, 0.94)***
Secondary	0.61 (0.58, 0.63)***	0.83 (0.79, 0.87)***
Higher	0.36 (0.32, 0.41)***	0.68 (0.59, 0.79)***
Mother’s occupation (Ref: Not employed)
Professional/office-related	0.45 (0.41, 0.50)***	0.88 (0.79, 0.98)*
Sales	0.95 (0.91, 0.98)**	1.02 (0.98, 1.06)
Farming	1.13 (1.10, 1.17)***	1.04 (1.00, 1.07)*
Other services	0.97 (0.93, 1.02)	1.01 (0.97, 1.05)
Father’s occupation (Ref: Not employed)
Professional/office-related	0.76 (0.72, 0.81)***	0.95 (0.85, 1.07)
Sales	1.13 (1.06, 1.20)***	1.02 (0.92, 1.14)
Farming	1.21 (1.16, 1.27)***	0.98 (0.88, 1.09)
Other services	0.95 (0.91, 1.01)	1.00 (0.90, 1.12)

^a Adjusted for kitchen location, country, residence and administrative provinces (provinces not shown), child’s sex, breastfeeding status, number of under-5 children, mother’s age and family size, wealth index, mother’s education, mother’s occupation, and father’s occupation.

^* p ≤ 0.05

^** p ≤ 0.01

^*** p ≤ 0.001.

Table 3. Hazard ratios (HRs) of risk of under-five mortality by cooking fuel and smoking in the household in Sub-Saharan Africa (n = 783,691).

Cooking fuel by smoking status	No. of dead children	No. of children	HR (95 % CI) ^a	RERIHR (95 % CI)	Attributable proportion due to interaction
Clean fuel
No smoking	1453	26,132	1.00
Smoking	369	5905	1.05 (0.86, 1.27)
Charcoal
No smoking	8692	89,603	1.18 (1.05, 1.32)**
Smoking	2691	22,282	1.40 (1.24, 1.58)***	0.17 (− 0.05, 0.38)	0.12 (− 0.04, 0.27)
Biomass
No smoking	61,689	466,620	1.19 (1.07, 1.33)**
Smoking	21,067	145,949	1.29 (1.15, 1.44)***	0.05 (− 0.16, 0.25)	0.04 (− 0.12, 0.19)
Other
No smoking	1932	24,087	1.00 (0.88, 1.13)
Smoking	268	3113	1.17 (0.92, 1.49)	0.12 (− 0.21, 0.45)	0.10 (− 0.16, 0.37)

^a Adjusted for kitchen location, country, residence and administrative provinces, child’s sex, number of under-5 children, mother’s age and family size, wealth index, mother’s education, mother’s occupation, and father’s occupation; RERI, relative excess risk due to interaction.

^** p ≤ 0.01

^*** p ≤ 0.001.