Relationship of employee turnover to exercise adherence in a corporate fitness program

The life table method of analysis was used to study the differences in turnover during a 4-year period among employees who participated in a corporate health and fitness program and those who did not. The study population consisted of 1,360 workers hired between Jan 1, 1982, and Dec 31, 1985, of whom 747 were exercisers; and 1,788 persons hired between Jan 1, 1978, and Dec 31, 1981, of whom 869 were exercisers. Age, sex, general job category, and duration of employment were taken into account in the analysis. For both groups the probability of continued employment among exercisers was significantly greater than among nonexercisers. The differences were particularly profound among female clerical employees. The study did not attempt to assess the causal nature of this relationship. However, we speculate that health and fitness programs influence turnover in employment groups where the personal financial benefits are the greatest.

Analysis of a corporation's health care experience: implications for cost containment and disease prevention

This article presents the health care experience of 14,162 employees and their families, covered under a private third-party insurance plan of a large multinational corporation for the 1984 policy year. A total of $29.5 million was charged by health care providers to deliver medical care for the studied employees and their families. This amounted to $2,083 per employee and his/her family. Approximately 51% of the employees submitted claims, with females having greater utilization than males. The highest expenditures were for diseases of the circulatory system among adults (3.2 million or 23% for employees, $1.5 million or 14% for spouses). Among employees, neoplasms accounted for $1.4 million or 10% of costs, and musculoskeletal system $1.2 million or 9% of costs. Among spouses, pregnancy and diseases of the female reproductive system accounted for $1.2 million (12%) and $1.1 million (10%), respectively. Among dependents, the top three cost categories were mental disorders ($1.2 million or 24%), accident-related illnesses ($0.7 million or 14%), and diseases of the respiratory system ($0.6 million or 12%). Hospital care expenditures, including room and board, ancillary, and physician services, accounted for approximately 60% of total health care spending. The percentage of health care costs paid for by this insurance plan was 75% for active employees, 34% for retirees, 60% for female spouses, 38% for male spouses, and 64% for dependents. The analyses and parameters measured can be viewed as the first step toward the development of a health care cost containment and disease prevention strategy.

A review of methodological issues of the standardized mortality ratio (SMR) in occupational cohort studies

This paper is a review and clarification of methodological issues related to the standardized mortality ratio (SMR), widely used in occupational epidemiology. Although the SMR seems to be a simple statistic, it can be misused and misinterpreted. The paper discusses SMRs in relation to age-specific mortality ratios, relative risk, life expectancy, and statistics derived from direct standardization. Inter-SMR comparisons and the effect of the choice of the comparison population on the SMR are also discussed. Mathematical and empirical review of SMR use has led to the development of a correction procedure which permits direct comparisons of two SMRs by adjusting for the age distributions of the two populations. The paper also proposes a method for testing the trend of age-specific mortality ratios (MRs). If MRs are homogeneous, this method can also be used to compare two SMRs. If MRs are not homogeneous, the relative risk between two sets of age-specific MRs can be tested for significance, but no summary index, including the SMR, can accurately describe the mortality experience over the entire age range. It is suggested that the summary statistics of a cohort mortality experience should include relative risk, attributable risk, and life expectancy. These statistics are complementary and can be derived or approximated from the data that generated the SMR. A valid risk assessment should weigh the evidence from all three summary statistics.

A preliminary investigation: effect of a corporate fitness program on absenteeism and health care cost

A random sample of 517 employees was studied to determine differences in health care costs and absenteeism among exercisers and nonexercisers during the start-up of a corporate health and fitness program. Exercise was associated with decreased illness absence among female exercisers (47 v 69 hours, P less than .05) and there was a trend for illness absence to be inversely related to advancing age among exercisers, whereas illness absence increased among nonexercisers. Total health care costs among exercisers was lower (male $561, females $639) than among nonexercisers (male $1,003, females $1,535). Due to the large variation in the individual cost, the differences between exercisers and nonexercisers were not statistically significant. Ambulatory health care cost for nonexercisers (males $486, females $883) were significantly higher than the costs for exercisers (males $408, females $243). Because the differences were found upon program initiation, they were thought to be characteristics of exercisers and not due to exercise itself.

Long-term mortality study of oil refinery workers: V. Comparison of workers hired before, during, and after World War II (1940-1945) with a discussion of the impact of study designs on cohort results

The mortality experience of a large refinery cohort (1937-1978) was examined by dividing it into three subcohorts according to hire dates: those hired before 1940, those hired during the period 1940-1945, and those hired after 1945. These three periods are approximately equivalent to before, during, and after World War II and span a total hiring period of more than 75 years. The results showed that a substantial portion of the cohort (3,330 or 27%) had been recruited during 1940-1945, and they contributed 980 or 28% of the total deaths. However, their mortality experience was quite different from the rest. A series of significant increases were seen among the external causes for accidents, suicide, and homicide. In terms of overall mortality and in contrast to the rest of the cohort, no "healthy worker effect" was seen (SMR = 1.00). They also showed increases in several types of cancer including cancers of the pancreas and prostate and leukemia. These unusual experiences cannot be explained either on the basis of their war-related deaths or on their period of employment (one-half were terminated within 1 year from date of hire), and data is insufficient to separate the role of hiring practices or their socioeconomic status. However, their life-styles were probably quite different judged from the fact that alcoholism-related deaths were increased as much as fivefold. Almost two-thirds of the total deaths occurred among 4,080 workers in the before 1940 subcohort. Further, the 5,117 workers of the after-1945 subcohort contributed only 5% of the total deaths. Thus, the results of the original refinery cohort (1937-1978) primarily reflect the experience of those employees hired before 1940. Given the same cohort method (historical prospective), cohort results vary widely according to different study designs, and this has implications for "generalizable" risk assessment or risk projections. A prospective study of new hires with 30 years of follow-up is rather inefficient because it would yield only a small number of deaths, with a strong healthy worker effect. The same is true for studies based on active workers with a short period of follow-up. Studies based on time of hire, however, provide a means for controlling time-related occupational exposures.

Long-term mortality study of oil refinery workers. IV. Exposure to the lubricating-dewaxing process

A retrospective cohort mortality study of 1,008 male oil refinery workers who ever worked on the lubricating-dewaxing process of the lube oil department and who have been followed for a period of 43 years is presented. These workers were exposed to a number of solvents, primarily methyl ethyl ketone [(MEK) CAS: 78-93-3] and toluene (CAS: 108-88-3), but at levels far below the current Occupational Safety and Health Administration's standard. The standardized mortality ratio (SMR) for all causes (0.70) and the SMR for cancer (0.86) are much lower than unity when they are compared to the mortality experience of the U.S. population. Also observed in this study were 8 prostate cancer deaths (4.4 expected) with an SMR of 1.82, which was not statistically significant (P = .16). Seven of these 8 prostate cancer deaths occurred among nonwhite males, who showed an SMR of 2.47 (P = 0.53). However, only 1 prostate cancer death was seen among workers specifically assigned to the MEK units. The remaining deaths occurred among maintenance workers who had lube oil department-wide assignments. This cancer risk increased with increasing duration of employment in the lube oil department. A latency of 20 years or more was also observed for these prostate cancer deaths. In this study the processing of lubricating oils was found to be at least as important as the MEK solvents, and department-wide maintenance workers were as much at risk as the MEK unit workers. In view of this finding and findings obtained by others, it seems prudent to continue to study lubricating-dewaxing process workers, including the medical monitoring of all such workers for prostate cancer.

The impact of competing risks on relative risks in occupational cohort studies

This paper develops a method for adjustment of competing causes of death in the calculation of relative risk. It has identified three factors determining the significance of competing risks: (1) the magnitude of the overall mortality risk of the study population; (2) differential risk (or the adjustment factor) for mortality other than cause of interest between two populations; and (3) age intervals used in the mortality calculation. Thus, the impact of competing risks is increased if the study cohort has a high mortality risk, if the mortality other than the cause of interest has a large differential risk or if the mortality calculation uses wide age intervals. Two examples from a refinery cohort and the US national population show that among certain age groups unadjusted for competing risks the relative risk is overestimated by 9%. The impact of competing risks in these two particular examples is relatively small. Furthermore, if relative risk is expressed in terms of the ratio of mortality rates, competing risks can be ignored.

A result-oriented medical information system. An alternative to the conventional approach

A result-oriented medical information system at the Gulf Oil Corporation is described. Mortality data acquired mostly from routine company operations have been used to calculate standardized mortality ratios (SMRs) and life expectancy. Results show that male employees at the age of 20 have a life expectancy of 74.8 years. Compared with the U.S. general population at age 20 with a life expectancy of 71.8 years, Gulf employees have an advantage of exactly three years. Such an advantage may seem small, but it is equivalent to the gain that could be achieved if all deaths from cancer were eliminated in the United States, a hypothetical and impossible situation. These life expectancy data have the potential for use by the company to influence insurance premiums traditionally set by life insurance companies as well as to aid in the management of the company's pension fund. The SMR for all causes for the male employees is 0.82, significantly decreased in comparison with that of the U.S. general population. This favorable experience has been referred to as "the healthy worker effect." Cause-specific SMRs show a generalized pattern of deficits, some of which are statistically significant. None showed a significant increase. Seventy-six percent of the male deaths occurred among employees aged 65 years or older. If these annuitants (those alive at the beginning of the study) were not included and only the active workers were studied, an SMR of only 0.54 would be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

A quantitative evaluation of competing risks in occupational studies

Mortality risk is competing because each individual is subject to several competing causes of death but can only die from one. Adjustment for competing risks will allow more meaningful comparisons of cause-specific mortality of two populations, especially if dying from all other causes is significantly different between the two populations. In this paper, a method has been developed for adjustment of competing causes of death in the calculation of relative risk. It identifies three factors as determining the significance of competing risks: (1) magnitude of the overall mortality risk of the study population; (2) differential risk or adjustment factor for all other causes between two populations; and (3) age interval used in mortality calculation. Thus, the impact of competing risks is increased if the mortality risk of the study population is high, if the differential risk for all other causes is large or if wide age intervals are used in the mortality calculation. An example from refinery cohort data shows that in certain age groups unadjusted for competing risks the relative risk is overestimated by 9%. The impact of competing risks in this particular example is relatively small.

Long-term mortality of oil refinery workers. II. Comparison of the experience of active, terminated and retired workers

In occupational epidemiology a retrospective cohort study normally includes active, terminated, and retired employees and the mortality results may vary considerably if any of the three groups is excluded from the study. From a large refinery cohort of 12,526 white male workers followed between January, 1937 and January, 1978, the mortality experience of three groups (the active, terminated and retired) has been examined; detailed results, along with the merits and problems of studying these groups separately, are presented. The standardized mortality ratios (SMRs) for all causes are 0.68, 1.04 and 0.89 for the active, the terminated and the retired, respectively, and for all cancer, 0.85, 0.98 and 1.05. Significantly decreased SMRs are seen for most of the causes among the active and may be attributed to the "healthy worker effect." Exclusive study of active workers, although it may yield certain useful information, particularly on diseases of the young and those with short latency periods, is primarily a study of the healthy worker effect. Many favorable effects of the active worker will be encountered. The retirees as a whole experienced no significant excess mortality for any causes, although examination of a subgroup, the early retirees, did reveal a significant excess of deaths from diseases of the nervous system and sense organs. The retired may appear to be an ideal group for study because they usually have worked for an extended period of time, they may have experienced long-term occupational exposure and they have lived long enough to develop diseases with long latency periods; however, serious problems arise from studying only the retirees and these are discussed. The terminated group contributed 41% of the person-years, 49% of the total number of individuals and 38% of the deaths and is far too important to be omitted. Contrary to previous reports, the terminated did not demonstrate a significantly adverse mortality experience when compared with the general population, although they did not show the healthy worker effect that was seen among the active.

Long-term mortality study of oil refinery workers. I. Mortality of hourly and salaried workers

This longitudinal study examined the mortality and cancer experience of workers at the Gulf Oil refinery located in Port Arthur, Texas. The cohort was studied over a period of 41 years, from 1937 to 1978, and consisted of 16,880 employees, with an accumulation of 406,198 person-years; 4361 deaths were observed. Emphasis of this study was placed on the experience of the hourly and salaried male workers employed one day or more and those with a minimum of one year employment. The standardized mortality ratio analysis revealed generally favorable mortality experience of the refinery workers, including that of overall cancer. Statistically significant deficits in mortality were found for several cancer sites including bladder, liver, and esophageal cancer. Many of the increased cancer risks suggested in the literature were not confirmed in this study. Although bone cancer was found to be increased significantly, review of those death certificates raises questions as to the accuracy of the recording and coding of this cancer. Sample size of this study is capable of providing sufficient statistical power for the detection of a twofold increase in mortality risk for many cancers, if such risk exists.

Retrospective mortality and medical surveillance studies of workers in benzene areas of refineries

The mortality and health experiences of refinery workers employed in benzene processes or operations are described. A retrospective cohort mortality study of benzene workers employed from 1952 to 1978 revealed no excess in overall general mortality or in cancer mortality compared either with the experience of the U.S. general population or with that of an internal control group. Ascertainment of vital status was accomplished for 99% of the cohort. Recent industrial hygiene data that included 1,394 personal samples indicated that 84% of all benzene exposures were less than 1 part per million (ppm), with a median exposure of 0.14 ppm for the refinery workers, and 0.53 ppm for those in the benzene-related units. Among these workers, no deaths from leukemia were observed. A medical surveillance program for benzene workers is also described, with special emphasis on the effectiveness of laboratory screening. Evaluation of data for a 21-year period showed no significant changes in the blood indices of the workers as a group. The limited value of establishing screening guidelines without the support of epidemiological studies is discussed.

Anatomy of the healthy worker effect: a critical review

The healthy worker effect is the composite result from factors such as (1) selection of the work force, (2) changes in lifestyle accompanying employment, and (3) methodological characteristics of the standardized mortality ratio (SMR). While the choice of the general population as the comparison population is the underlying reason for this effect, no more feasible, widely accepted or "better" alternative is yet available. Much of the current understanding of the healthy worker effect has been limited to an examination of selection of the work force. The purpose of this report is to illustrate, using examples from a large cohort study, the importance of many factors other than selection. They include employment-associated benefits such as economic gain, medical insurance and lifestyle changes, the proportion of active workers, the calculation method, data completeness, length of follow-up and certain characteristics of SMR methodology. It is shown that some of the healthy worker effect is characteristic of SMR methodology and that the strength of the healthy worker effect depends on the proportion of active workers in the cohort. Furthermore, the disappearance of the healthy worker effect may be due to factors such as aging of the cohort and can be totally unrelated to the true increase in the mortality risk. In other words, its disappearance, in many instances, may be an artifact of SMR methodology.

Changes in life expectancy in the United States due to declines in mortality, 1968-1975

This study examines the gains in life expectancy for four race/sex groups of the US population between 1968 and 1975. An increase of 2.3 years in life expectancy at birth and 1.7 years in life expectancy at age 45 years has occurred for all race/sex groups combined. The added years of life for the normal working ages (15-70 years) is only 0.6 years for the total US population, 0.3 years for white females, 0.6 years for white males, 1.5 years for nonwhite males, and 1.7 years for nonwhite females. The relative contribution of the five leading causes of death to this gain varies at different ages. For example, more than 50% of the increase in life expectancy at age 45 years was due to a lower mortality rate in diseases of the heart which is still the leading cause of death among each of the race/sex groups. Other contributions to the increase in life expectancy at age 45 years are: cerebrovascular diseases, 16%; accidents, 6%; influenza and pneumonia, 7%; and all other causes, 16%. The increase in the malignant neoplasms mortality rate had a negative effect, -2%, on the gain of life expectancy.

The effect of a reduction in leading causes of death: potential gains in life expectancy

The potential gains in total expectation of life and in the working life ages among the United States population are examined when the three leading causes of death are totally or partially eliminated. The impressive gains theoretically achieved by total elimination do not hold up under the more realistic assumption of partial elimination or reduction. The number of years gained by a new-born child, with a 30 per cent reduction in major cardiovascular diseases would be 1.98 years, for malignant neoplasms 0.71 years, and for motor vehicle accidents 0.21 years. Application of the same reduction to the working ages, 15 to 70 years, results in a gain of 0.43, 0.26, and 0.14 years, respectively for the three leading causes of death. Even with a scientific break-through in combating these causes of death, it appears that future gains in life expectancies for the working ages will not be spectacular. The implication of the results in relation to the current debate on the national health care policy is noted.