Changes in Physical Fitness and Changes in Mortality

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IntroductionStudies based on point estimates of physical fitness showthat such estimates are a good long-term predictor ofcardiovascular mortality and all-cause mortality in healthypeople.17 However, these studies generally assume ahomogenous decline in physical fitness with agethroughout the population. Patterns of physical fitnessmay in fact vary between subgroups because of, forexample, changes in physical activity and smoking habitsover time: the Global Burden of D isease Study8 putsphysical inactivity and smoking among the top ten risk

factors that threaten global health. Information onchanges in physical fitness and lifestyle may provide moreinformation on long-term prognosis than can be obtainedfrom a single estimate.

To study the relations between physical fitness,changes in physical fitness, and mortality, we tested thephysical fitness of a group of apparently healthy middle-aged men. The men were tested on two occasions, withan interval of 7 years. Total follow-up time was 22 years.

Participants and methodsParticipants2014 men aged 4060 years took part in a baseline survey(survey 1) in 197275.9 Men were defined as apparently

healthy if they had no evidence of heart disease, no diagnosedhypertension requiring drug treatment, and no diabetes mellitus,cancer, advanced pulmonary, renal, or liver disease, or otherserious disorders, and were able to undertake a symptom-limitedexercise test. 1756 (91%) of the men participated in a secondidentical survey in 198082 (survey 2), and our study uses thesedata.

258 of the participants in survey 1 did not participate insurvey 2. Of these, 92 had died45 from cardiovascular causes,27 from cancer, and 20 from other causes. Of the remaining166 men who did not take part in survey 2, 47 were too ill toparticipate, 47 had too far to travel, and 72 gave no reasons fornon-participation. Among the 1756 men who took part in thesecond survey, 328 were excluded for one or more of thefollowing reasons: myocardial infarction (72), stroke (nine),angina pectoris (114), cancer (23), diabetes mellitus (32),

pulmonary, renal, or liver diseases (41), hypertension requiringdrug treatment (150), and inability to do the exercise test (21).Thus, data from 1428 men were included in our analysis. Forthese 1428 men, follow-up started at the date of survey 2 andended by Dec 31, 1994.

1456 (86%) of the original cohort were surveyed for a thirdtime in 198990 (survey 3), and some of these most recent datawere used to check our models.

Survey methodsThe methods of surveys 1 and 2 were the same.5,9,10,11 Allparticipants had a clinical examination, with blood tests,spirometry, a chest radiograph, measurements of height andweight, and an exercise electrocardiographic (ECG) test. Theexercise test used an electrically braked bicycle, which demandeda constant output of energy at each workload irrespectiveof pedalling rate. T he test workload was set at 1405 kcal/min(100 W) to begin with, and was increased by 0703 kcal/min

Summary

Background Point estimates of physical fitness give

important information on the risk of death in healthy

people, but there is little information available on effects of

sequential changes in physical fitness on mortality. We

studied this latter aspect in healthy middle-aged men over

a total follow-up period of 22 years.

Methods 2014 healthy men aged 4060 years had a

bicycle exercise test and clinical examination, and

completed a questionnaire in 197275 (survey 1). This

was repeated for 1756 (91%) of 1932 men still alive by

Dec 31, 1982 (survey 2). The exercise scores were

adjusted for age. The change in exercise scores between

surveys was divided into quartiles (Q1=least fit,

Q4=fittest). An adjusted Coxs proportional hazards model

was used to study the association between changes in

physical fitness and mortality, with the Q1 men used as

controls.

Findings By Dec 31, 1994, 238 (17%) of the 1428 men

had died, 120 from cardiovascular causes. There were 37

deaths in the Q4 group (19 cardiovascular); their relative

risks of death were 045 (95%CI 029069) for any cause

and 047 (026086) for cardiovascular causes. There

was a graded, inverse relation between changes in

physical fitness and mortality irrespective of physical

fitness status at survey 1.

Interpretation Change in physical fitness in healthy middle-

aged men is a strong predictor of mortality. Even small

improvements in physical fitness are associated with a

significantly lowered risk of death. If confirmed, these

findings should be used to influence public health policy.

Lancet1998; 352: 75962

Changes in physical fitness and changes in mortality

Gunnar Erikssen, Knut Liestl, Jrgen Bjrnholt, Erik Thaulow, Leiv Sandvik, J an Erikssen

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THE LANCET Vol 352 September 5, 1998 759

Medical Department, Central Hospital of Akershus, N-1474

Nordbyhagen, Norway (G Erikssen MD, J Erikssen MD); Institute of

Informatics, University of Oslo, Blindern, Norway (K Liestl PhD);

Medical Department B, National Hospital, Oslo, Norway

(J Bjrnholt MD, E Thaulow MD); and Medstat Research A/ S,

Lillestrom, Norway (L Sandvik PhD)

Correspondence to: Dr Gunnar Erikssen

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(50 W) every 6 min. T he men were encouraged to exercise toexhaustion or for as long as they were willing to continue.5Totalwork capacity was calculated as the sum of all work done at allworkloads, and physical fitness was defined as total workcapacity divided by bodyweight.

Physical activity codes were based on a questionnaire.12 Weclassified as physically active men who took physical exerciseat least twice a week that caused sweating and shortness of

breath, or took part in sporting activities.12

Physical-fitness scoresin surveys 1 and 2 are referred to as PF1 and PF2 respectively.

Data collectionAll mortality and morbidity data were collected after having beengranted legal permission from the Norwegian Data Inspectorateand the Norwegian Board of H ealth to study death records inthe database of Statistics Norway covering all deaths occurring inNorway, and all relevant patient records in Norwegian hospitals.Sudden deaths and deaths from ischaemic heart disease, stroke,and other arteriosclerotic diseases were classed as cardiovasculardeaths. M ortality data are complete as of Dec 31, 1994.

Statistical methodsSince both physical fitness and mortality are related to age, westandardised our data accordingly. Standard mortality ratios are

based on the mortality rates for 1990 reported by StatisticsNorway. After log-transformation, both PF1 and PF2 decreasedin a linear manner as a function of age, and their dispersionaround regression lines was virtually independent of age. Age-adjusted quartiles of the distribution of PF1 and PF2 (Q1=leastphysically fit, Q4=fittest) were set around these regression lines.

We used Coxs proportional-hazards model to study theassociation between physical fitness, cardiovascular mortality,and all-cause mortality, adjusted for the quartiles of physicalfitness, and for age, systolic blood pressure, heart rate, bloodconcentrations of total cholesterol and triglycerides, body-massindex, amounts of physical activity, exercise results, and smokingstatus. Diagnostic plots of log S(t) versus log (t) showed that theassumptions of the proportional-hazards model were acceptable.Control runs with time-dependent covariates, which usedinformation from survey 3, gave similar results to the standardCox models.

Our results are given as relative risks of death. For continuousvariables, relative risks associated with increases of 1 SD aregiven. For discrete variables (physical fitness, exercise-testresults, smoking status, amounts of physical activity) relativerisks were calculated between groups. Pearsons 2 test was usedto compare mortality between groups, and the Kendall rank testwas used to assess any correlation between continuous variablesor between ordinal variables. Statistical analyses used StatView(version 4.5) and S+ (version 3.4) computer programs.

ResultsThe results of survey 2 (table 1) show significant variationaccording to age-adjusted physical fitness in bloodconcentrations of triglycerides, heart rate, systolic bloodpressure, body-mass index, amounts of physical activity,vital capacity, smoking status, and exercise-ECG

findings. For all these variables, the highest quartile ofphysical fitness had the values indicating lowest risk.

Total cholesterol concentration was not significantlyassociated with physical fitness. Between-group variationsin physical fitness were associated with only smallvariations in body-mass index.

By the end of 1994, 238 (167%) of the 1428 men whoparticipated in survey 2 had died, from cardiovascularcauses (120), cancer (75), and other causes (43). Wefound an inverse relation between all-cause mortality andphysical fitness (table 2). With only physical fitness andage as predictors of all-cause mortality, the relative risk ofdeath in quartiles Q2, Q3, and Q4 compared with theleast fit quartile Q1 were 063, 037, and 031respectively. With a larger set of risk factors included(table 3), the relations between all-cause mortality,cardiovascular mortality, and physical fitness remainedsimilar. Of all the parameters included in the model, onlysmoking status, resting heart rate, systolic blood pressure,and vital capacity appeared as confounders of thepredictive power of physical fitness. Another Cox model,which used total work capacity as the measure of physicalfitness and bodyweight as a separate variable, gave similarresults. Thus, physical fitness was a strong predictor ofcardiovascular and total mortality even when other riskfactors were taken into account.

Although there was a good correlation between PF1and PF2 (r=074), many of the men had changed theirstandard of physical fitness by survey 2. T able 4 groupsparticipants according to quartiles of PF1 and accordingto quartiles of changes in physical fitness from PF1 toPF2. In five of the 16 subquartiles, PF2 was higher thanPF1 (ratio>100). T o illustrate what this change means interms of exercise capacity, for the least fit quartile atsurvey 1 (PF1 Q1) those who increased physical fitnessmost (PF2/PF1 Q4), the PF2/PF1 ratio was 136% and

the change in exercise capacity was only 2 min at bicycleload 2 (150W).

Overall, our data show that there was a graded, inverserelation between changes in physical fitness and mortalityirrespective of physical fitness at survey 1. Proportional-hazards analysis that included all risk factors, PF1, and

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Characteristic Mean (SD) or % in age-adjusted physical-fitness quartile (PF2)

Q1 (n=357) Q2 (n=357) Q3 (n=357) Q4 (n=357) All (n=1428)

Age (years) 567 (54) 565 (56) 561 (50) 571 (56) 566 (54)

PF2 (KJ/ kg) 0763 (0245) 1171 (0263) 1519 (0293) 2054 (0573) 1377 (0600)

Smokers 47% 39% 29% 16% 33%*

Physically active 78% 112% 151% 350% 173%*

Resting heart rate (bpm) 67 (11) 64 (10) 63 (9) 60 (10) 63 (10)*

Systolic blood pressure (mm Hg) 133 (20) 131 (18) 130 (17) 129 (17) 131 (18)*

Vital capacity (mL) 3689 (836) 4031 (780) 4268 (760) 4450 (781) 4110 (839)*Total cholesterol (mmol/ L) 66 (13) 64 (12) 64 (12) 64 (11) 64 (12)

Triglycerides (mmol/ L) 17 (11) 14 (10) 14 (07) 12 (06) 14 (09)*

Body-mass index (kg/ m2) 251 (33) 247 (27) 256 (25) 242 (22) 247 (27)*

Positive-exercise ECG 22% 17% 16% 13% 17%

Q1=least physically fit, Q4=fittest. * p for trend


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changes in physical fitness (log[PF2/PF1]), showed thatchanges in physical fitness have a highly significant effecton all-cause mortality (p


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the lowest maximum heart rate (10% of the total studygroup) did not significantly affect our results. Adjustmentfor body size in our definition of physical fitness was ofmarginal significance, and changes in bodyweight overtime did not affect our results for physical fitness orchanges in fitness.

Up to 30% of the men in survey 1 maintained or even

increased their fitness by survey 2. Some men may havehad undetected, intercurrent disorders at survey 1, whichled to poor exercise-test results, but the overall increase infitness was more likely to be linked to increases in leisure-time activity, giving up smoking, or both.15,16 It may berelevant that all participants in survey 1 received a writtenreport of the results, and that those who were less fitreceived various recommendations for improving theirhealth. Increased public awareness of the beneficialeffects of giving up smoking and increased exercise mayalso have played a part in the observed increase in fitnessduring follow-up.

Physical fitness is influenced by genetic factors (40%)and other factors (60%).17 Genetic causes of differences

in physical fitness are difficult to measure. T he effects ofphysical activity on fitness are more easily assessed. Themost rapid declines in fitness between survey 1 andsurvey 2 were probably caused by changes in lifestyle,development of subclinical disease, or both. T hebeneficial effects on long-term physical fitness of givingup smoking, and the detrimental effects of continuing tosmoke, are well known.16 A good standard of physicalfitness has beneficial effects on serum lipidconcentrations, fibrinolysis, glucose tolerance and insulinmetabolism, platelet function, blood pressure,autonomic-system function, myocardial electric stability,dimensions of the coronary arteries,5 and the immunesystem.18

In our study, good physical fitness was associated witha favourable risk-factor profile, and improvements inphysical fitness were associated with improvements inrisk-factor profile. Followup studies based on single testsof physical fitness17 show similar results to ours,irrespective of selection procedures, methods, and follow-up, as do published data on physical activity.1926To ourknowledge, only one other study has used data onrepeated tests of physical fitness,27 and the results accordwith ours. Although our study was observational, thefitness data were corrected for several importantconfounders and the results seem biologically plausible.A large-scale, prospective, randomised study is needed totest these theories further, but such a study may not bepossible.

Many people rely on drug therapies and medicalinterventions to improve their health. We have shownthat physical fitness is associated with a lowered risk ofdeath, and that improvement in physical fitness over timealso further reduces this risk. The men in our study whowere and remained physically fit had the most favourableprognosis. However, according to these data, probablythe most important suggestion is that moderateimprovements in physical fitness, particularly amongthose who are least fit, bring substantial benefits tohealth.

ContributorsGunnar Erikssen designed the study, analysed the data, and had the mainresponsibility for writing the paper. Knut Liestl provided scientific

guidance and contributed to data analysis. Jan Erikssen initiated the firstsurvey in 1972. Jrgen Bjrnholt undertook data collection. Erik Thaulowcollected data and was involved in planning the study. L eiv Sandvik did

statistical analysis of the database. All investigators contributed to thewriting of the paper.

AcknowledgmentWe thank I Erikssen for valuable secretarial assistance.

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Changes in Physical Fitness and Changes in Mortality