berkey98 {mixmeta}

Five Published Trials on Periodontal Disease

Description

The dataset contains the results of 5 published trials comparing surgical and non-surgical treatments for medium-severity periodontal disease, one year after treatment. The 2 estimated outcomes are average improvements (surgical minus non-surgical, in mm) in probing depth (PD) and attachment level (AL).

Usage

berkey98

Format

A data frame with 5 observations on the following 7 variables:

pubyear

publication year of the trial.

npat

number of patients included in the trial.

PD

estimated improvement of surgical versus non-surgical treatments in probing depth (mm).

AL

estimated improvement of surgical versus non-surgical treatments in attachment level (mm).

var_PD

variance of the estimated outcome for PD.

cov_PD_AL

covariance of the estimated outcomes for PD and AL.

var_AL

variance of the estimated outcome for AL.

Row names specify the author of the paper reporting the results of each trial.

Source

Berkey CS, et al. (1998). Meta-analysis of multiple outcomes by regression with random effects. Statistics in Medicine. 17:2537–2550.

Berkey CS., et al. (1995). Multiple-outcomes meta-analysis of treatments for periodontal disease. Journal of Dental Research. 74(4):1030–1039.

Sera F, Armstrong B, Blangiardo M, Gasparrini A (2019). An extended mixed-effects framework for meta-analysis.Statistics in Medicine. 2019;38(29):5429-5444. [Freely available here].

Examples

### REPRODUCE THE RESULTS IN BERKEY ET AL. (1998)

# INSPECT THE DATA
berkey98

# FIXED-EFFECTS
year <- berkey98$pubyear - 1983
mod1 <- mixmeta(cbind(PD,AL) ~ year, S=berkey98[5:7], data=berkey98,
  method="fixed")
print(summary(mod1), digits=3)

# GLS MODEL (VARIANCE COMPONENTS)
mod2 <- mixmeta(cbind(PD,AL) ~ year, S=berkey98[5:7], data=berkey98,
  method="vc",  control=list(vc.adj=FALSE))
print(summary(mod2), digits=3)
round(mod2$Psi, 3)

# ML MODEL
mod3 <- mixmeta(cbind(PD,AL) ~ year, S=berkey98[5:7], data=berkey98, method="ml")
print(summary(mod3), digits=3)
round(mod3$Psi, 3)