1 / 9

Analysis of Cross-Sectional Studies

Analysis of Cross-Sectional Studies. In cross-sectional studies outcome and exposure variables are measured simultaneously, and temporal sequence between cause and outcome cannot be determined.

jadon
Download Presentation

Analysis of Cross-Sectional Studies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Analysis of Cross-Sectional Studies • In cross-sectional studies outcome and exposure variables are measured simultaneously, and temporal sequence between cause and outcome cannot be determined. • In the study described here, diabetic subjects with hypertension were prescribed β-blockers and the investigators wanted to assess the effect on blood levels of HDL-2. • The subjects varied with regard to age, the severity of diabetes, body weight, smoking and alcohol use, and blood levels of triglycerides and C-peptide.

  2. HDL-2 levels (effects of smoking and alcohol use) Mean HDL-2 level is higher among those who use alcohol and amongst non-smokers.

  3. HDL-2 levels and Age With increasing age HDL-2 levels tend to be lower but the relationship is not very strong. R-sq = 3.3 %

  4. HDL-2 levels and Blood Glucose and Triglycerides

  5. HDL-2 levels and Weight With increasing body weight the HDL-2 levels tend to be lower. R-sq.= 4.6%

  6. HDL-2 levels and Beta-blockers Administration of Beta-blocker tends to bring down HDL-2 levels. Bearing in mind that high levels of HDL-2 are protective against heart disease diabetic subjects with hypertension needs careful follow-up

  7. Multiple Regression • The research question is asking the effect of β-blockers on HDL-2 levels. This was shown in the previous slide. But Other factors like life-style, age , body weight and so on also influence HDL-2 levels. Taking all these factors together we get the following as the regression equation. The regression equation is HDL = 0.711 - 0.0824 Beta - 0.0173 Alco - 0.0399 Smok - 0.00455 Age - 0.00214 wt - 0.0444 Trigl. + 0.00463 C-pep - 0.00391 Gluc. S = 0.07745 R-Sq = 59.5% R-Sq(adj) = 54.3%

  8. Regression Diagnostic • Advisable to check that assumptions of regression analysis are not violated. In a clinical observational study one may not be able to do much but at least one knows how much one can depend on the results.

  9. Regression Diagnostic - II • To look for unusual data points one need to plot residuals against fitted values. These two plots are of residuals and standardised residuals against fitted values.

More Related