Maximal exercise testing variables and 10-year survival: fitness risk score derivation from the FIT Project.
OBJECTIVE
To determine which routinely collected exercise test variables most strongly correlate with survival and to derive a fitness risk score that can be used to predict 10-year survival.


METHODS
This was a retrospective cohort study of 58,020 adults aged 18 to 96 years who were free of established heart disease and were referred for an exercise stress test from January 1, 1991, through May 31, 2009. Demographic, clinical, exercise, and mortality data were collected on all patients as part of the Henry Ford ExercIse Testing (FIT) Project. Cox proportional hazards models were used to identify exercise test variables most predictive of survival. A "FIT Treadmill Score" was then derived from the β coefficients of the model with the highest survival discrimination.


RESULTS
The median age of the 58,020 participants was 53 years (interquartile range, 45-62 years), and 28,201 (49%) were female. Over a median of 10 years (interquartile range, 8-14 years), 6456 patients (11%) died. After age and sex, peak metabolic equivalents of task and percentage of maximum predicted heart rate achieved were most highly predictive of survival (P<.001). Subsequent addition of baseline blood pressure and heart rate, change in vital signs, double product, and risk factor data did not further improve survival discrimination. The FIT Treadmill Score, calculated as [percentage of maximum predicted heart rate + 12(metabolic equivalents of task) - 4(age) + 43 if female], ranged from -200 to 200 across the cohort, was near normally distributed, and was found to be highly predictive of 10-year survival (Harrell C statistic, 0.811).


CONCLUSIONS
The FIT Treadmill Score is easily attainable from any standard exercise test and translates basic treadmill performance measures into a fitness-related mortality risk score. The FIT Treadmill Score should be validated in external populations.
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD.
Haitham M
HM
Ahmed
Department of Cardiac Imaging, King Abdulaziz Cardiac Center, Riyadh, Kingdom of Saudi Arabia; Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI.
Mouaz H
MH
Al-Mallah
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD.
John W
JW
McEvoy
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD; Center for Prevention and Wellness Research, Baptist Health Medical Group, Miami Beach, FL; Department of Medicine, Herbert Wertheim College of Medicine, Miami, FL; Department of Epidemiology, Robert Stempel College of Public Health and Social Work, Miami, FL.
Khurram
K
Nasir
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD.
Roger S
RS
Blumenthal
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD.
Steven R
SR
Jones
Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI.
Clinton A
CA
Brawner
Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI.
Steven J
SJ
Keteyian
Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD. Electronic address: mblaha1@jhmi.edu.
Michael J
MJ
Blaha
D000328:Adult; D000368:Aged; D002423:Cause of Death; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment; D016019:Survival Analysis