How your lifestyle affects your longevity.

How Your Lifestyle Affects Your Longevity

When the first life table (a favorite tool of statisticians to estimate how long people will live) on Seventh-day Adventists (SDAs) was published in 1967, it provided quite a surprise to scholars and others interested in longevity. It showed that California SDAs, compared to the general population, had a real advantage in life expectancy. This research gave rise to the often-quoted figure that a 35-year-old SDA California man had a 6.2-year longer life expectancy than a non-SDA California man. It was commonly thought that this advantage primarily resulted from the SDA practice of not smoking.

In the intervening 21 years a number of questions have arisen: How do various lifestyle practices influence longevity? How does a vegetarian or other special diet influence longevity? Do such lifestyle practices as exercise, maintaining optimal weight, or avoiding stress make a big difference in one's longevity? Meanwhile, a series of research projects at Loma Linda University has been focusing on SDAs. We know a lot more now about length of life and probability of death. We are now better able to answer these questions.

Research on SDAs has long been a topic of keen interest to both the scientific community and the general public. During the past 29 years there have been more than 149 research publications on various aspects of Adventist health. These reports, many showing benefits of the Adventist lifestyle, have been published mostly in scientific journals not easily accessible to the general public. Consequently, the public has not been fully informed about the benefits of the Adventist lifestyle.

These reports have had an important impact on both scientists and government officials. After hearing a research report on diet and the lower mortality of SDAs, one scientist remarked: "It appears that the best insurance that one can take out today is to follow the lifestyle of Adventists." In 1980 Sidney Katz, a Canadian official, reviewed a report on the benefits of the Adventist lifestyle. He wrote in MacLean's magazine: "I've got some advice on how to improve the health of Canadians and, at the same time, lop billions of dollars off our annual health costs. I think we should study the lifestyle of adherents of the Seventh-day Adventist Church and then explore ways and means of persuading the public to emulate the Adventists in at least some ways."

When Congress was considering health guidelines for the nation, the Senate select committee studying the topic used findings on Adventists to come up with its recommendations. As government planners try to explore the implications of a longer life span for more and more Americans, they carefully review what is likely to happen as more people adopt more beneficial lifestyles. For this reason, some scientists view the studies of SDAs as "a peek into the future" of what the U.S. population may well experience in the coming decades as they move to a revised lifestyle.

Studies of Adventists have contributed significantly to scientific knowledge regarding the development of cancer, heart disease, and stroke. Hence government agencies have supported a variety of research conducted at Loma Linda University over the past 15 years. A recent New York Times article suggested that the data collected on Adventists is a "gold mine" for bringing to light new scientific evidence regarding lifestyle and health.

Research into lifestyle and health is not limited to Loma Linda. Such work goes on at many other universities. One of the landmark studies of health practices and mortality was conducted by Belloc and Breslow at the Human Population Laboratory. The study was done on 6,928 individuals near San Francisco. In 1980, in a 12-year follow-up of this group, Breslow and Enstrom identified seven lifestyle practices that related closely to improved longevity. These were: not smoking, little or no alcohol consumption, exercising, eating breakfast, not snacking, not being overweight, and sleeping seven to nine hours per night. Men who followed three or fewer of these experienced a mortality rate that was nearly four times higher than men who adhered to all seven of them. This knowledge now provides a sound scientific basis for the long-held belief that good health practices can directly influence longevity.

The carefully collected lifestyle information on SDAs is scientifically unique in that it gives us an opportunity to look at the longevity of vegetarians. In 1960 Dr. Frank Lemon, then on the Loma Linda University faculty, agreed to cooperate with the American Cancer Society's (ACS) study of 1 million persons. The objective of the ACS study was to determine the factors associated with the development of cancer. A total of 27,514 California SDAs, then 30 years or older, participated in this study. They completed a questionnaire that inquired into diet, smoking, physical activity, stress, and other personal characteristics. The SDAs were followed over the subsequent 26 years. During that time 3,101 men and 4,782 women participants died. The data allowed us to determine the influence of the various factors on longevity.

We compared the average age at death of various subgroups classified by lifestyle characteristics. Then we compared vegetarians to nonvegetarians. Using this approach, we were able to observe the influence of various lifestyle factors on how long people lived. Male vegetarians attained, on average, 80.5 years; nonvegetarians, 75.3 years. The difference between vegetarian (81.6) and nonvegetarian (77.8) women was 3.8 years. The groups were further divided according to the amount of refined foods they consumed. A refined foods index (RFI) was constructed to measure each person's intake of what some people would call "not-so-healthy foods." It provided an indication of how frequently a person used such foods as candy, catsup, mayonnaise, fried foods, salt and pepper, soft drinks, spaghetti, pancakes, sweet desserts, and coffee.

Table 1 shows that, on average, death came 3.9 years later for vegetarian men with a more healthful diet (low RFI) than those with a high RFI. A difference of 3.7 years was observed for nonvegetarian men. Women with low RFI experienced a postponement of death of about 3.4 years. These findings tell us that vegetarians enjoy an increased longevity that can be extended even further by adopting a more healthful (low RFI) diet. Even nonvegetarians benefit from a low RFI diet. Exercise was also important. Men who exercised moderately or heavily had a longevity advantage of 2.2 to 2.6 years over those who did not exercise or exercised only slightly. We were unable to determine the effect of exercise in women because the study did not gather data for them. The benefit of exercise on longevity is further supported by the results of the Harvard alumni study, which reported that the more active alumni lived longer than the inactive.

Smoking is always an issue of special interest. Because few SDAs reported themselves as "current smokers," we concentrated on comparing differences in longevity between "never smokers" and "past smokers." For men, never smokers outlived past smokers by 2.0 years in vegetarians and 2.3 years in nonvegetarians. The difference between never smokers and the few current smokers among men was 9.1 years in vegetarians and 8.0 years in nonvegetarians. For women, differences in longevity between never and past smokers was 7.3 years for vegetarians and 8.8 years for nonvegetarians. A number of long-term studies reported by the U.S. surgeon general have shown that a two-pack-a-day smoker, aged 30 to 35, shortens his life expectancy by eight to nine years. But the big differences we found in longevity between never smokers and past smokers differ with the surgeon general's report, which contends that after 15 years the mortality risk of quitters equates that of never smokers. Our research shows there is a difference that persists: about two years for men and about eight years for women. Just why women never smokers enjoy such a large advantage is not yet clear at this time.

Body weight also proved to have an influence on longevity. Normal-weight men had a 1.8- to 1.9-year advantage when compared to overweight men. Normal-weight women, if vegetarian, enjoyed a 2.1-year advantage over their overweight counterparts, or a 1.4-year advantage if nonvegetarian. The implication is that obese individuals tend to die earlier.

This is supported by a recent publication of the National Institutes of Health, The Health Implications of Obesity. It states that obesity has an adverse effect on health and longevity, and further shows that obese individuals have a three times greater risk of developing high blood pressure or diabetes. Furthermore, obese men experience higher mortality from colon, rectal, and prostate cancer, while women experience higher mortality from breast, uterine, ovarian, and gallbladder cancer. With 34 million obese Americans, this indeed represents a heavy public health problem.

We also wanted to know what would be the combined effect of adopting several health habits. This was accomplished by constructing a health habit index (HHI), which added the scores of each health habit. Individuals with high scores had many health habits, and those with low scores had few health habits. Habits such as exercise, diet, smoking, drinking, sleeping, eating breakfast, weight, and others were included in this index. The study group was then divided into those with low, medium, and high HHI scores. Men with high HHI scores were contrasted with those having low HHI scores. We found that vegetarian men with many health habits lived, on the average, 5.4 years longer than vegetarians with few health habits. Nonvegetarians with high HHI scores lived 7.5 years longer than nonvegetarians with few health habits. For women, these figures were 6.1 years for vegetarians and 3.9 years for nonvegetarians.

Our study subjects also provided an indicator of whether or not they experienced stress. Men having no stress achieved a longevity advantage of 5.7 years for vegetarians and 7.5 years for nonvegetarians. Women without stress had a longevity advantage of 4.4 years for vegetarians and 4.7 years for nonvegetarians.

Researchers feel that many of the 44 million Americans suffering from hypertension and the 7 million suffering from low back pain are in reality experiencing an underlying stress. These conditions often lead to premature death. Since lifestyles can be changed, individuals are in a good position to decrease their chances of succumbing to these illnesses by developing means of coping with stress and adopting improved health habits. This could lead to an improvement in one's health and ultimately to greater longevity.

Our research leads us to conclude that persons who adopt a vegetarian lifestyle, have an adequate exercise program, maintain normal weight, quit smoking, and manage their stress are able to enjoy a significantly higher longevity.

The better longevity of SDAs is not unique to California. Three European studies of SDAs, based on smaller populations, show an SDA life expectancy higher than that of their corresponding countrymen, more so for men than for women. In this study of 522 SDAs in the Netherlands, Berkel reported an 8.9-year life expectancy advantage for men and 3.7 for women. Waaler and Hjort, who studied 9,336 Norwegian SDAs, reported a 4.2-year advantage for men and 1.9 for women. In Poland, SDA men were reported to have an average difference in age at death of 9.5 years, and SDA women had a difference of 4.5 years.

In summary, we found that the improved longevity of SDAs observed in this analysis supports the previous findings but adds some fresh points. In 1969 it appeared that the primary reason was not smoking. Now the results suggest that diet, exercise, stress, and weight each have an influence. Our individual lifestyle choices may have even more influence on longevity than improvements in the quality of health care. Perhaps a paraphrase of a famous quote from President John F. Kennedy's 1960 inaugural address would be in order: "Ask not what the health-care system can do to extend your life; ask what you yourself can do."

The payoff for following good health practices was clearly voiced by King Solomon: "My son, forget not my law; but let thine heart keep my commandments; for length of days, and long life, and peace, shall they add to thee" (Prov. 3:1, 2).

Jan Kuzma, Ph.D., is chairman of the biostatistics program and director of research at the School of Public Health, Loma Linda University, Loma Linda, California.