Abstract
Relative risk estimates suggest that effective implementation of behaviors commonly advocated in preventive medicine should increase life expectancy, although there is little direct evidence. Objective To test the hypothesis that choices regarding diet, exercise, and smoking influence life expectancy. Methods A total of 34 192 California Seventh-Day Adventists (75% of those eligible) were enrolled in a cohort and followed up from 1976 to 1988. A mailed questionnaire provided dietary and other exposure information at study baseline. Mortality for all subjects was ascertained by matching to state death tapes and the National Death Index. Results California Adventists have higher life expectancies at the age of 30 years than other white Californians by 7.28 years (95% confidence interval, 6.59-7.97 years) in men and by 4.42 years (95% confidence interval, 3.96-4.88 years) in women, giving them perhaps the highest life expectancy of any formally described population. Commonly observed combinations of diet, exercise, body mass index, past smoking habits, and hormone replacement therapy (in women) can account for differences of up to 10 years of life expectancy among Adventists. A comparison of life expectancy when these factors take high-risk compared with low-risk values shows independent effects that vary between 1.06 and 2.74 years for different variables. The effect of each variable is assessed with all others at either medium- or high-risk levels. Conclusions Choices regarding diet, exercise, cigarette smoking, body weight, and hormone replacement therapy, in combination, appear to change life expectancy by many years. The longevity experience of Adventists probably demonstrates the beneficial effects of more optimal behaviors.
Generated Summary
This research article investigates the relationship between lifestyle choices and life expectancy, focusing on a cohort of California Seventh-Day Adventists. The study employs a cohort design, following a group of over 34,000 individuals from 1976 to 1988. Data on diet, exercise, smoking habits, and other lifestyle factors were collected via questionnaires, and mortality data was obtained through state death records and the National Death Index. The primary objective was to assess how choices related to diet, exercise, and smoking influence life expectancy. The study’s approach involves multivariate analysis and the use of life table methods to estimate the impact of various lifestyle factors on predicted lifespan. The researchers aimed to predict the expected length of life in subjects who adhere to different behaviors to evaluate the associations with mortality. This approach allowed the researchers to quantify the effects of specific lifestyle choices on longevity and to compare the life expectancy of Adventists to that of the broader Californian population.
Key Findings & Statistics
- Life Expectancy Differences: California Adventists exhibited higher life expectancies compared to other white Californians. Specifically, men had 7.28 years (95% confidence interval, 6.59-7.97 years) and women had 4.42 years (95% confidence interval, 3.96-4.88 years) more life expectancy at age 30.
- Risk Factor Values: The study analyzed various risk factors among Adventists. It was found that 28% to 31% of the subjects were vegetarian, 23% consumed nuts at least 5 times per week, and about 40% exercised vigorously for 15 minutes at least 3 times per week. Additionally, more men than women were past smokers, and 53% of postmenopausal women had ever used hormone replacement therapy (HRT).
- Vegetarianism and Life Expectancy: Vegetarian Adventist men and women had expected ages at death of 83.3 and 85.7 years, respectively.
- Impact of Specific Behaviors: The study examined the effects of changing individual variables on life expectancy. The results ranged between 1.06 and 2.74 years for different variables.
- Multivariate Estimates: Multivariate estimates revealed the impact of various factors. For instance, vegetarianism (compared to non-vegetarianism) showed a difference in life expectancy of 1.53 years for men and 1.51 years for women (medium risk). High exercise (compared to low exercise) resulted in a difference of 2.73 years for men and 1.88 years for women (medium risk). High nut consumption provided a difference of 2.74 years for men and 1.87 years for women (medium risk). When covariates were at high risk, vegetarianism showed a difference of 2.38 years for men and 1.65 years for women. High exercise resulted in 2.14 years for men and 2.19 for women. High nut consumption showed a difference of 2.87 years for men and 1.18 years for women.
- Combined Effects: The study also looked at the combined effects of various factors. The combined effect of these factors could lead to a significant increase in life expectancy.
- Mortality Causes: Of the observed deaths, 1373 (26.4%) were attributed to coronary heart disease, 1074 (20.7%) to cancer, and 531 (10.2%) to stroke.
- Impact of Hypertension and Diabetes: The impact of hypertension and diabetes on life expectancy was also considered. For instance, the effects on life expectancies when these disorders were modeled to begin at age 55 years, rather than age 30 years, resulted in reductions of 3.8 and 2.8 years in male and female hypertensive subjects, respectively.
- Impact of Smoking: Smoking could not be evaluated in this study.
Other Important Findings
- The study’s findings suggest that the choices related to diet, exercise, and smoking have a significant impact on life expectancy.
- The longevity experienced by Adventists likely demonstrates the beneficial effects of optimal health behaviors.
- The study indicates that the combined effect of diet, exercise, body mass index, past smoking habits, and hormone replacement therapy can account for differences of up to 10 years in life expectancy among Adventists compared to the general population.
- The research indicates that approximately half of the Adventist men and women may be losing more than 4 years of life due to suboptimal behavioral choices.
- The study’s results suggest that a shift towards more healthful behaviors could yield a significant increase in life expectancy.
Limitations Noted in the Document
- Cohort Limitations: The study is limited by the characteristics of the cohort, as the Adventist population may not be fully representative of the general population.
- Volunteer Effect: The volunteer status of participants could introduce bias, potentially influencing the comparisons with the broader Californian population.
- Data Limitations: While the study used extensive data, including questionnaires and mortality records, the reliance on self-reported data may introduce errors.
- Smoking Evaluation: The absence of current smokers in the population made it impossible to assess the impact of current cigarette smoking.
- Generalizability: The study acknowledges that its findings may not be directly applicable to all ethnic groups, as the sample consisted solely of non-Hispanic whites.
- Confounding Factors: The effects of the lifestyle factors may be influenced by unknown confounding variables, which could impact the accuracy of the results.
- Limited Scope: The study focused on a limited set of lifestyle factors and did not include all potential factors that might influence life expectancy.
Conclusion
The study’s findings strongly suggest that behavioral choices have a substantial impact on life expectancy, potentially influencing it by several years, and even a decade in some cases. The results emphasize the importance of adopting healthier behaviors, such as improving diet, increasing physical activity, avoiding smoking, and managing body weight, as these are associated with a longer lifespan. The study’s observations on the Adventist population suggest that the benefits of such choices can be generalized to other populations. The observed effects of lifestyle choices on the study population are not limited to a specific group; the benefits are likely applicable to a broader range of individuals. This conclusion is supported by the fact that changing the values of covariates to high-risk levels did not significantly alter the estimated effects of the lifestyle variables. The findings of this research align with the broader recommendations for preventive medicine, which advocate for lifestyle changes to improve health outcomes. The researchers’ estimations suggest the potential for substantial gains in life expectancy through changes in lifestyle patterns, specifically by adopting more optimal health behaviors. The study’s results support the idea that such changes may yield a significant increase in life expectancy if implemented on a wider scale.
IFFS Team Summary
- Data on 7th Day Adventists in California compared to other western populations in the world
- Cohort of 34000 men and women followed for 12 years
- Increased lifespan of up to 10 years depending on the following factors: vegetarian diet, exercise, nut consumption, smoking status and BMI
- Note that BMI is also improved by a plant diet
- does not include vegan subgroup