In this module, you will use NHANES data
to assess the association between several risk factors and the
likelihood of having hypertension for participants 20 years and
older. The dependent variable Y is hypertension, and the independent
variables X_{j}, or covariates, are age, gender, high
cholesterol, body mass index, and fasting triglycerides. In this task , you will only be reviewing the Multivariate Logistic
Procedure.

In order to subset the data in SAS Survey Procedures, you will need to create a variable for the population of interest. You should not use a where clause or by-group processing in order to analyze a subpopulation with the SAS Survey Procedures.

In this example, the* sel *variable is set to 1 if the sample person is 20 years or older, and 2 if the sample person is younger than 20 years. Then this variable is used in the domain statement to specify the population of interest (those 20 years and older).

if ridageyr GE 20 then sel = 1;

else sel = 2;

This step introduces you to the SAS multivariate survey Logistic Regression
procedure, *proc surveylogistic*. There is a summary table of the SAS program below.

IMPORTANT NOTE

These programs use variable formats listed in the Tutorial Formats page. You may need to format the variables in your dataset the same way to reproduce results presented in the tutorial.

Statements | Explanation |
---|---|

DATA = Analysis_Data nomcar; |
Use the |

STRATUM sdmvstra; |
Use the |

CLUSTER sdmvpsu; |
Use the |

WEIGHT wtsafyr; |
Use the |

DOMAIN sel; | Use the |

CLASS
age (PARAM=REF REF= '40-59
yrs' )
riagendr (PARAM=REF REF='Female' ) hichol (PARAM=REF REF='high cholesterol' ) bmigrp (PARAM=REF REF='25<=BMI<30' ); |
Use the
Use the |

MODEL hyper (desc)=age riagendr hichol bmigrp logtrig/ vadjust=none; |
Use the |

format age
agefmt. riagendr
sexfmt. hichol
chfmt. bmigrp
bmifmt. ; ; |
Use the |

WARNING

The SAS Survey Procedure, *proc surveylogistic,* produces the
Wald statistic and its p value. It does not produce the Satterthwaite χ^{2} or the Satterthwaite
F and the corresponding p values recommended for NHANES
analyses. For this reason, **it is recommended that you
use proc rlogist in SUDAAN for logistic
regression**.

In this step, the SAS output is reviewed. You can compare your results with the sample output, which you can download from the Sample Code and Datasets page. Or, you can view an animated version of the results with narration by clicking the link below. In the narration, the highlighted elements show that:

- 1,304 respondents have hypertension and 2,515 do not.
- The beta coefficients and odds ratio point estimates are identical to the SUDAAN estimates.