Table 3.
Morbidity Index^ and Health^, Six-term Sociodemographic Base Models Multivariate generalized additive regression models (GAM) are designed to estimate and evaluate curvilinearity. Each term is controlled for all others in the model. Data are from the National Health Interview Survey 1987 Cancer Epidemiology Supplement (N=17,612)
| Morbidity Model | Health Model | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Variables | Nonlinearity | Variables | Nonlinearity | |||||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | ||||||
| Variables | Levels | Coef.* | Rsq∼ | sig† | nl.df | nl.sig† | Coef.* | Rsq∼ | sig† | nl.df | nl.sig† | |
| 1 | Sex | Male | ||||||||||
| Female | .66 | .005 | 0 | – | – | .07 | .001 | 7.4E-6 | – | – | ||
| 2 | Race | White | ||||||||||
| Black | −.01 | .23 | ||||||||||
| Hispanic | −.78 | .002 | 4.4E-8 | – | – | .00 | .004 | 0 | – | – | ||
| 3 | Marital | Never:Alone | ||||||||||
| status: | Never:Others | −.31 | .10 | |||||||||
| Living | Mar:Spouse | −.14 | .11 | |||||||||
| arrangement | Div:Alone | .51 | −.00 | |||||||||
| Div:Others | 1.10 | .08 | ||||||||||
| Sep:Alone | .09 | .08 | ||||||||||
| Sep:Others | .12 | −.10 | ||||||||||
| Wid:Alone | .40 | .003 | 4.8E-9 | − | − | .17 | .003 | 1.1E-10 | − | − | ||
| Wid:Others | ||||||||||||
| 4 | Education | Elementary | ||||||||||
| Jr. high | −.34 | −.12 | ||||||||||
| HS grad | −.76 | −.34 | ||||||||||
| Any college | −.43 | −.44 | ||||||||||
| College grad.+ | −.65 | .002 | 1.5E-9 | − | − | −.60 | .018 | 0 | − | − | ||
| 5 | Income◊ | .015 | 0 | 3.1 | 1.0E-9 | .021 | 0 | 3.1 | 0 | |||
| 6 | Age◊ | .026 | 0 | 2.3 | .002 | .055 | 0 | 2.3 | 4.4E-16 | |||
| Base model | Intcpt‡ | Rsq∼ | Intcpt‡ | Rsq∼ | ||||||||
| 3.92 | .112 | 0 | 2.40 | .212 | 0 | |||||||
Mar=married; Div=divorced; Sep=separated; Wid=widowed.
Morbidity Index (none to 30 points) is a composite of seven NHIS variables. Health is self-assessed (Excellent=1 to Poor=5). See Methods section in text.
Categorical term coefficients contrast the first with subsequent levels.
Rsq Approx. R-squared estimated from change in deviance residuals when variable of interest is dropped from 11-term model.
Significance estimates are from F-tests comparing the 6-term model to a five-term model, dropping the variable of interest.
P-values less than 1.0×10−4 are written as 1.0E-4; p-values less than 10E-16 are given as zero.
Predicted mean value of outcome, the model intercept, is plotted as zero on Y-axis in plots of model terms. Model intercept, predicted mean value of outcome, is zero on Y-axis in plots of model terms. See Figures.
Nonlinearity significance indicates whether a curved term is statistically preferable to a linear version.
Continuous functions estimated with S-Plus GAM lo() smoother (span=1/2 of data).