nafld {survival} R Documentation

## Non-alcohol fatty liver disease

### Description

Data sets containing the data from a population study of non-alcoholic fatty liver disease (NAFLD). Subjects with the condition and a set of matched control subjects were followed forward for metabolic conditions, cardiac endpoints, and death.

### Usage

nafld1
nafld2
nafld3
data(nafld, package="survival")


### Format

nafld1 is a data frame with 17549 observations on the following 10 variables.

id

subject identifier

age

age at entry to the study

male

0=female, 1=male

weight

weight in kg

height

height in cm

bmi

body mass index

case.id

the id of the NAFLD case to whom this subject is matched

futime

time to death or last follow-up

status

0= alive at last follow-up, 1=dead

nafld2 is a data frame with 400123 observations and 4 variables containing laboratory data

id

subject identifier

days

days since index date

test

the type of value recorded

value

the numeric value

nafld3 is a data frame with 34340 observations and 3 variables containing outcomes

id

subject identifier

days

days since index date

event

the endpoint that occurred

### Details

The primary reference for the NAFLD study is Allen (2018). The incidence of non-alcoholic fatty liver disease (NAFLD) has been rising rapidly in the last decade and it is now one of the main drivers of hepatology practice Tapper2018. It is essentially the presence of excess fat in the liver, and parallels the ongoing obesity epidemic. Approximately 20-25% of NAFLD patients will develop the inflammatory state of non-alcoholic steatohepatitis (NASH), leading to fibrosis and eventual end-stage liver disease. NAFLD can be accurately diagnosed by MRI methods, but NASH diagnosis currently requires a biopsy.

The current study constructed a population cohort of all adult NAFLD subjects from 1997 to 2014 along with 4 potential controls for each case. To protect patient confidentiality all time intervals are in days since the index date; none of the dates from the original data were retained. Subject age is their integer age at the index date, and the subject identifier is an arbitrary integer. As a final protection, we include only a 90% random sample of the data. As a consequence analyses results will not exactly match the original paper.

There are 3 data sets: nafld1 contains baseline data and has one observation per subject, nafld2 has one observation for each (time dependent) continuous measurement, and nafld3 has one observation for each yes/no outcome that occured.

### Source

Data obtained from the author.

### References

AM Allen, TM Therneau, JJ Larson, A Coward, VK Somers and PS Kamath, Nonalcoholic Fatty Liver Disease Incidence and Impact on Metabolic Burden and Death: A 20 Year Community Study, Hepatology 67:1726-1736, 2018.

[Package survival version 3.5-5 Index]