Estimating neighbourhood-level socio-economic effect on preterm births using a multilevel approach: a case study in Georgia, USA

Figures & data

Figure 1. Percentage of raw preterm births at the County level in Georgia, USA, 1995–2000.

Table 1. Individual- and neighbourhood-level descriptors based on Georgia 2000 Vital Records and census data and used in the logistic regression analysis.

Variable	Method of computation/unit	Mean ± SD (% for categorical variables with the value of 1)
Individual characteristics (N = 117,329)
Gestation weeks	<37 weeks = 1; ≥37 weeks = 0	10.2%
Race/ethnicity	White = 1; black = 2; others = 3	63.5%
Sex of the newborn baby	Male = 1; female = 0	50.9%%
Mother’s age	Years-25	26.48 ± 6.11
Mother’s marital status	Married = 1; unmarried = 2	63%
Mother’s year of education	Years	12.77 ± 2,75
Mother received late or no prenatal care	Yes = 1; No = 0	12.6%
Mothers’ previous foetal deaths	Numbers	0.23 ± 0.61
Mother used alcohol during pregnancy	Yes = 1; No = 0	0.7%
Mother used tobacco during pregnancy	Yes = 1; No = 0	8.2%
Neighbourhood (Census Tract) characteristics (N = 1618)
Variable	Method of computation/unit	Mean ± SD
Poverty	% population living below federal poverty	15.91 ± 12.29
Female household head	% families with female headed household with dependent children	34.23 ± 14.98
Household income	% households with income less than *$25,000	32.89 ± 17.24
Public assistance income	% households receiving public assistance income	3.55 ± 3.67
Occupation	% in management	29.41 ± 13.35
Household size	Average household size, person per room	2.63 ± 0.34
Unemployment	% unemployed population	3.93 ± 3.93
Education	% population with no high school education	8.89 ± 6.36
Means of transportation	% households with no (owned or rented) vehicle	10.42 ± 11.55

Table 2. Results of ordinary and multilevel logistic regression models.

	GLM		M0	M1		M2
	OR	95% CI		OR	95% CI	OR	95% CI
Level 1-individual N = 117,329
Race (reference: white)
Black	1.4513	(1.38,1.52)		1.4874	(1.42,1.56)	1.4509	(1.38,1.52)
Sex (reference: male)
Female	0.8912	(0.86,0.93)		0.8912	(0.86,0.93)	0.8912	(0.86,0.93)
AGE25	1.0103	(1.01,1.01)		1.0102	(1.01,1.01)	1.0106	(1.01,1.01)
Marital Status (reference: married)	1.1829	(1.13,1.24)		1.1935
Unmarried					(1.14,1.25)	1.1835	(1.13,1.24)
Education	0.9725	(0.96,0.98)		0.9689	(0.96,0.98)	0.9714	(0.96,0.98)
Prenatal care	1.1829	(1.15,1.28)		1.2134	(1.15,1.28)	1.1835	(1.14,1.28)
Foetal death	1.2098	(1.1,1.16)		1.1320	(1.1,1.17)	1.2077	(1.10,1.16)
Alcohol use	1.1041	(0.89,1.37)		1.1143	(0.9,1.38)	1.1113	(0.89,1.38)
Tobacco use	1.3099	(1.23,1.4)		1.3018	(1.22,1.39)	1.2974	(1.21,1.39)
Level 2-census tract N = 1613
IoD	1.0065	(1.0029,1.0101)				1.0064	(1.0025,1.0104)
IOR-80%						(0.74,1.36)
Measures of census tract-level variation
MOR			1.280	1.175		1.171
ICC			0.0201	0.0086		0.0083
PVC				57.4%		59.0%
Model selection
AIC	74,862		75,695		74,845	74,837