Determinants of body mass index by gender in the Dikgale Health and Demographic Surveillance System site, South Africa

Figures & data

Table 1. Demographics, socio-economic, behavioural and biological characteristics by gender.

	Women (n = 796) n (%)	Men (n = 347) n (%)	p-values
Response/outcome variable
BMI (kg/m^2)*	30.1 (25.2–35.8)	20.6 (18.9–24.3)	< 0.001
BMI categories
Underweight	24 (3)	69 (20)	< 0.001
Normal weight	166 (21)	205 (59)
Overweight	198 (25)	63 (18)
Obese	408 (51)	10 (3)
Socio-demographics
Age (years)	51 (46–56)	50 (45–55)	0.233
40–44	154 (19)	80 (23)	0.533
45–49	186 (23)	75 (22)
50–54	201 (25)	87 (25)
55–60	255 (32)	105 (30)
Marital status
Never married or cohabited	179 (23)	98 (28)	0.094
Married/living with partner	418 (53)	174 (50)
Divorced/Widowed	199 (25)	75 (22)
Level of education
No formal education	72 (9)	21 (6)	0.116
Primary	268 (34)	109 (31)
Secondary	432 (54)	200 (58)
Tertiary	24 (3)	17 (5)
Employment Status
Unemployed	523 (66)	188 (54)	< 0.001
Employed	273 (34)	159 (46)
SES
1^st quintile	82 (10)	63 (18)	0.004
2^nd quintile	179 (23)	83 (23)
3^rd quintile	109 (14)	43 (12)
4^th quintile	182 (23)	64 (18)
5^th quintile	244 (31)	94 (27)
Housing density (People/room)	1.0 (0.7–1.3)	1.0 (0.7–1.7)	< 0.001
Behavioural
Diet
Bread intake (servings/day) *	1.7 (0.9–3.0)	1.7 (0.6–3.0)	0.138
Fruit and vegetable intake (servings/day)*	1.3 (0.9–2.3)	1.3 (0.9–2.3)	0.707
Sugar sweetened beverages (servings/day)*	0.3 (0.3–0.6)	0.3 (0.3–0.7)	0.047
Smoking status
Never	743 (93)	52 (15)	< 0.001
Current smoked	24 (3)	220 (63)
Former smoker	29 (4)	75 (22)
Use alcohol
Never	551 (69)	52 (15)	< 0.001
Current non-problematic	44 (6)	75 (22)
Current problematic	56 (7)	139 (40)
Former Consumer	145 (18)	81 (23)
Physical Activity and Sleep
MVPA (minutes/week)*	300 (200–480)	360 (180–600)	< 0.001
MVPA Categories
Inactive (< 150minutes/week)	80 (10)	47 (13)	0.084
Active (≥ 150minutes/week)	716 (90)	300 (87)
Sleep (hours/night)*	9.0 (8.0–10.0)	9.6 (8.4–10.3)	< 0.001
Biological
HIV status
HIV negative	612 (78)	267 (79)	0.647
HIV positive	175 (22)	71 (21)
Number of pregnancies	5.0 (3.0–6.0)	-	-
Menopausal status			-
Pre-menopausal	255 (32)	-
Peri-menopausal	81 (10)	-
Post-menopausal	377 (48)	-
Not staged	83 (10)	-

*Not normally distributed data expressed as median (IQR) and categorical data expressed as n (%), SES – Socioeconomic status, MVPA – Moderate to Vigorous Physical Activity, HIV – Human immunodeficiency virus; missing HIV = 18

Table 2. Bivariate linear modeling (unstandardized beta coefficient) for the association of BMI with demographic, socio-economic, behavioural, and biological factors for women and men.

	Women (n = 796)		Men (n = 347)
	Coefficient (95%CI)	p-values	Coefficient (95%CI)	p-values
Socio-demographic factors
Age	−0.002 (−0.004, 0.002)	0.273	0.001 (−0.001, 0.004)	0.482
Marital Status
Never married or cohabited	Ref		Ref
Married/living with partner	0.06 (0.02, 0.11)	0.008	0.08 (0.04, 0.12)	< 0.001
Divorced/Widowed	0.02 (−0.03, 0.07)	0.483	−0.005 (−0.06, 0.04)	0.842
Level of education
No formal education	Ref		Ref
Primary	0.03 (−0.04, 0.09)	0.391	0.02 (−0.06, 0.09)	0.707
Secondary	0.07 (0.004, 0.013)	0.036	0.02 (−0.05, 0.10)	0.551
Tertiary	0.03 (−0.09, 0.15)	0.627	0.09 (−0.03, 0.19)	0.133
Employment Status
Unemployed	Ref		Ref
Employed	0.01 (−0.02, 0.05)	0.488	0.02 (−0.01, 0.06)	0.188
SES
1^st quintile	Ref		Ref
2^nd quintile	0.05 (−0.01, 0.12)	0.107	0.005 (−0.05, 0.06)	0.857
3^rd quintile	0.09 (0.02, 0.17)	0.010	0.06 (−0.003, 0.12)	0.063
4^th quintile	0.09 (0.03, 0.16)	0.005	0.07 (0.009, 0.13)	0.023
5^th quintile	0.15 (0.09, 0.21)	< 0.001	0.09 (0.04, 0.15)	< 0.001
Housing density (People/room)	−0.01 (−0.03, 0.02)	0.611	−0.007 (−0.03, 0.02)	0.660
Behavioural factors
Diet
Bread intake (Servings/day)	0.02 (0.01, 0.03)	< 0.001	0.007 (−0.003, 0.02)	0.188
Fruit/vegetable intake (servings/day)	0.01 (−0.001, 0.02)	0.132	−0.0003 (−0.008, 0.007)	0.930
Sugar sweetened beverages (servings/day)	0.03 (0.01, 0.06	0.005	0.02 (−0.005, 0.04)	0.131
Smoking status
Never	Ref		Ref
Current smoked	−0.19 (−0.29, −0.08	< 0.001	−0.14 (−0.19, −0.09)	< 0.001
Former smoker	−0.04 (−0.14, 0.05)	0.394	−0.06 (−0.12, −0.002)	0.044
Use alcohol
Never	Ref		Ref
Current non-problematic	−0.01 (−0.08, 0.07)	0.901	−0.12 (−0.19, −0.06)	< 0.001
Current problematic	−0.10 (−0.17, −0.03)	0.005	−0.13 (−0.19, −0.08)	< 0.001
Former Consumer	−0.01 (−0.06, 0.03)	0.561	−0.07 (−0.13, −0.02)	0.014
Physical Activity and Sleep
MVPA (minutes/week)	0.00008 (−0.0007, 0.00009)	0.843	−0.00002 (0.00008, 0.00004)	0.446
MVPA Categories
Inactive (< 150min/wk)	Ref		Ref
Active≥ 150min/wk)	−0.03 (−0.09, 0.03)	0.257	−0.03 (−0.08, 0.03)	0.326
Sleep (hours/night)	−0.02 (−0.03, −0.01)	< 0.001	−0.02 (−0.03, −0.007)	0.002
Biological factors
HIV status
HIV negative	ref		Ref
HIV positive	−0.13 (−0.17, −0.08)	< 0.001	−0.06 (−0.10, −0.01)	0.012
Number of pregnancies	0.005 (−0.002, 0.01)	0.170	-	-
Menopausal status
Pre-menopause	Ref		-	-
Peri	−0.009 (−0.07, 0.06)	0.779	-	-
Post	−0.04 (−0.12, 0.04)	0.313	-	-
Not staged	−0.05 (−0.11, 0.01)	0.125	-	-

SES – Socioeconomic status, MVPA – Moderate to Vigorous, Physical Activity, HIV – Human immunodeficiency virus, min/wk – minutes/week

Table 3. Sex-stratified hierarchical models showing demographic, socio-economic, behavioural and biological factors associated with log BMI for women.

	Model 1 Demographic and socioeconomic factors		Model 2 Demographic, socio-economic and behavioural factors		Model 3 Demographic, socio-economic, behavioural and biological factors
	Coeff (95%CI)	p-value	Coeff (95%CI)	p-value	Coeff (95%CI)	p-value
Age (years)	−0.002 (−0.005, 0.001)	0.280	−0.002 (−0.005, 0.001)	0.267	−0.004 (−0.008, −0.0009)	0.012
Marital Status
Never married or cohabited	Ref		Ref		Ref
Married/living with partner	0.05 (−0.001, 0.09)	0.053	0.05 (0.005, 0.09)	0.029	0.03 (−0.02, 0.08)	0.220
Divorced/Widowed	0.02 (−0.03, 0.08)	0. 390	0.03 (−0.03, 0.08)	0.338	0.03 (−0.03, 0.08)	0.345
Level of education
No formal education	Ref		Ref		Ref
Primary	0.02 (−0.05, 0.09)	0.560	0.003 (−0.06, 0.07)	0.922	0.005 (−0.06, 0.07)	0.887
Secondary	0.04 (−0.03, 0.11)	0.256	0.010 (−0.05, 0.08)	0.698	0.008 (−0.06, 0.08)	0.821
Tertiary	−0.03 (−0.15, 0.9)	0.654	−0.07 (−0.19, 0.05)	0.258	−0.07 (−0.19, 0.05)	0.248
SES
1^st quintile	Ref		Ref		Ref
2^nd quintile	0.05 (−0.01, 0.12)	0.117	0.04 (−0.02, 0.10)	0.279	0.03 (−0.04, 0.09)	0.370
3^rd quintile	0.09 (0.01, 0.17)	0.016	0.07 (−0.004, 0.14)	0.064	0.07 (−0.004, 0.14)	0.064
4^th quintile	0.09 (0.02, 0.15)	0.012	0.07 (−0.001, 0.13)	0.054	0.07 (0.007, 0.14)	0.031
5^th quintile	0.14 (0.07, 0.21)	< 0.001	0.11 (0.04, 0.17)	0.002	0.10 (0.03, 0.17)	0.003
Diet
Bread intake (Servings/day)			0.01 (0.0004;0.02)	0.041	0.007 (−0.004, 0.02)	0.228
Fruit/vegetable intake (servings/day)			0.00 (−0.005, 0.01)	0.435	0.007 (−0.002, 0.02)	0.118
Sugar sweetened beverages (servings/day)			0.02 (−0.0008, 0.05)	0.058	0.02 (−0.003, 0.04)	0.081
Smoking status
Never			Ref		Ref
Current smoked			−0.14 (−0.25, −0.03)	0.010	−0.15 (−0.26, −0.05)	0.005
Former smoker			−0.02 (−0.12, 0.07)	0.638	−0.02 (−012, 0.08)	0.674
Use alcohol
Never			Ref		Ref
Current non-problematic			0.01 (−0.06, 0.09)	0.713	0.04 (−0.05, 0.11)	0.411
Current problematic			−0.06 (−0.13, 0.01)	0.108	−0.05 (−0.13, 0.02)	0.151
Former Consumer			0.005 (−0.04, 0.05)	0.840	0.0 (−0.03, 0.06)	0.482
Sleep (hours/night)			−0.02 (−0.03, −0.003)	0.013	−0.02 (−0.03, −0.003)	0.015
HIV Status
HIV negative					Ref
HIV Positive					−0.13 (−0.17, −0.08)	< 0.001
Number of pregnancies					0.003 (−0.005, 0.01)	0.445
R^2	0.044		0.081		0.116
Adjusted R^2	0.032		0.059		0.092
F (p-value)	< 0.001		< 0.001		< 0.001
Mean VIF (min, max)	2.28 (1.20,3.56)		1.75 (1.07, 3.71)		1.73 (1.07,3.87)

SES – Socioeconomic status, HIV – Human immunodeficiency virus

Table 4. Sex-stratified hierarchical models showing demographic, socio-economic, behavioural and biological factors associated with log BMI for men.

	Model 1 Demographic and socioeconomic factors		Model 2 Demographic, socio-economic and behavioural factors		Model 3 Demographic, socio-economic, behavioural and biological factor
	Coeff (95%CI)	p-value	Coeff (95%CI)	p-value	Coeff (95%CI)	p-value
Age (years)	0.001 (−0.002, 0.004)	0.445	0.0007 (−0.002, 0.004)	0.643	−0.0004 (−0.003, 0.003)	0.816
Marital Status
Never married or cohabited	Ref		Ref		Ref
Married/living with partner	0.06 (0.02, 0.11)	0.003	0.08 (0.04, 0.12)	< 0.001	0.09 (0.05, 0.13)	< 0.001
Divorced/Widowed	−0.01 (−0.07, 0.04)	0.623	0.02 (−0.03, 0.06)	0.503	0.04 (−0.02, 0.09)	0.135
Level of education
No formal education	Ref		Ref		Ref
Primary	−0.009 (−0.09, 0.07)	0.816	0.009 (−0.07, 0.09)	0.803	−0.01 (−0.09, 0.06)	0.743
Secondary	−0.006 (−0.08, 0.07)	0.881	0.005 (−0.07, 0.08)	0.901	−0.02 (−0.09, 0.05)	0.589
Tertiary	0.02 (−0.09, 0.13)	0.674	0.04 (−0.07, 0.15)	0.448	0.006 (−0.10, 0.11)	0.911
Employment status
Unemployed	Ref		Ref		Ref
Employed	0.02 (−0.01, 0.06)	0.217	0.02 (−0.02, 0.06)	0.265	0.02 (−0.02, 0.05)	0.365
SES
1^st quintile	Ref		Ref		Ref
2^nd quintile	0.004 (−0.05, 0.06)	0.877	−0.00008 (−0.05, 0.05)	0.998	−0.005 (−0.05, 0.04)	0.839
3^rd quintile	0.05 (−0.02, 0.11)	0.153	0.04 (−0.02, 0.11)	0.174	0.04 (−0.03, 0.09)	0.257
4^th quintile	0.06 (−0.003, 0.11)	0.062	0.04 (−0.02, 0.09)	0.226	0.03 (−0.2, 0.09)	0.274
5^th quintile	0.09 (0.03, 0.14	0.003	0.07 (0.01, 0.12)	0.017	0.07 (0.02, 0.13)	0.009
Diet
Bread intake (Servings/day)			0.002 (−0.008, 0.01)	0.640	0.002 (−0.008, 0.01)	0.679
Sugar sweetened beverages (servings/day)			0.009 (−0.01, 0.03)	0.373	0.007 (−0.01, 0.03)	0.506
Smoking status
Never			Ref		Ref
Current smoked			−0.10 (−0.16, −0.04)	< 0.001	−0.09 (−0.16, −0.04)	< 0.001
Former smoker			−0.04 (−0.11, 0.02)	0.188	−0.04 (−0.01, 0.02)	0.216
Use alcohol
Never			Ref		Ref
Current non-problematic			−0.07 (−0.13, −0.006)	0.032	−0.08 (−0.14, −0.01)	0.016
Current problematic			−0.07 (−0.13, −0.003)	0.041	−0.07 (−0.14, −0.01)	0.023
Former Consumer			−0.05 (−0.12, 0.01)	0.113	−0.05 (−0.11, 0.02)	0.149
Sleep (hours/night)			−0.008 (−0.02, 0.003)	0.142	−0.007 (−0.01, 0.003)	0.189
HIV Status
HIV negative					Ref
HIV Positive					−0.08 (−0.12, −0.03)	< 0.001
R^2	0.105		0.218		0.248
Adjusted R^2	0.076		0.172		0.200
F (p-value)	< 0.001		< 0.001		< 0.001
Mean VIF (min, max)	2.08 (1.05,4.59)		2.19 (1.10,4.89)		2.16 (1.10–4.93)

SES – Socioeconomic status, HIV – Human immunodeficiency virus