Abstract
Previous research suggests that Adventists, who often follow vegetarian diets, live longer and have lower risks for many cancers than others, but there are no national data and little published comparative data for black subjects. METHODS: This study compared all-cause mortality and cancer incidence between the nationally inclusive Adventist Health Study 2 (AHS-2) and nonsmokers in US Census populations: the National Longitudinal Mortality Study (NLMS) and its Surveillance, Epidemiology, and End Results substudy. Analyses used proportional hazards regression adjusting for age, sex, race, cigarette smoking history, and education. RESULTS: All-cause mortality and all-cancer incidence in the black AHS-2 population were significantly lower than those for the black NLMS populations (hazard ratio [HR] for mortality, 0.64; 95% confidence interval [CI], 0.59-0.69; HR for incidence, 0.78; 95% CI, 0.68-0.88). When races were combined, estimated all-cause mortality was also significantly lower in the AHS-2 population at the age of 65 years (HR, 0.67; 95% CI, 0.64-0.69) and at the age of 85 years (HR, 0.78; 95% CI, 0.75-0.81), as was cancer mortality; this was also true for the rate of all incident cancers combined (HR, 0.70; 95% CI, 0.67-0.74) and the rates of breast, colorectal, and lung cancers. Survival curves confirmed the mortality results and showed that among males, AHS-2 blacks survived longer than white US subjects. CONCLUSIONS: Substantially lower rates of all-cause mortality and cancer incidence among Adventists have implications for the effects of lifestyle and perhaps particularly diet on the etiology of these health problems. Trends similar to those seen in the combined population are also found in comparisons of black AHS-2 and NLMS subjects. Cancer 2019;0:1-10. © 2019 American Cancer Society.
Generated Summary
This research article presents a study that compares all-cause mortality and cancer incidence rates between a national Seventh-Day Adventist (SDA) population and a representative sample of the U.S. population. The study utilized data from the Adventist Health Study 2 (AHS-2) and the National Longitudinal Mortality Study (NLMS), along with a SEER substudy of the NLMS (SEER-NLMS) for cancer incidence data. The methodology involved proportional hazards regression, adjusting for various factors such as age, sex, race, smoking history, education, and region of residence. The primary aim was to assess the impact of lifestyle factors, particularly diet, on health outcomes by comparing the health profiles of Adventists, who often follow vegetarian diets, with those of the general population. The study’s scope encompassed all-cause mortality, the incidence of all cancers combined, and the incidence of specific cancers, including breast, colorectal, rectal, and lung cancers. The analysis compared outcomes between the AHS-2 population and the NLMS and SEER-NLMS populations, focusing on the differences in mortality and cancer incidence rates. The study also examined the black AHS-2 population in comparison to the black NLMS population to explore health disparities and the influence of lifestyle within different racial groups. The data collection included extensive questionnaires and record linkages with cancer registries. The study period spanned from 2002 to 2011, with subjects followed for new cancer diagnoses. The research provides insights into the effects of lifestyle on the etiology of health problems.
Key Findings & Statistics
- Total Subjects: NLMS: 383,600; AHS-2: 86,610; SEER-NLMS: 62,074; AHS-2: 79,641.
- Race Distribution (NLMS): White: 89%; Black: 11%.
- Race Distribution (AHS-2): White: 73%; Black: 27%.
- Mortality (NLMS): 35,230 deaths; AHS-2: 7250 deaths.
- Former Smokers (NLMS): 30%; AHS-2: 19%.
- All-cause mortality: Significantly lower in the AHS-2 population compared to NLMS (model-estimated HR at age 65: 0.67; P < 0.0001; at age 85: 0.78; P < 0.0001).
- Cancer Incidence: Significantly lower in the AHS-2 population (HR: 0.70; P < 0.0001).
- Black Population All-cause Mortality (AHS-2 vs. NLMS): HR: 0.64; P < 0.0001.
- Black Population Cancer Incidence (AHS-2 vs. SEER-NLMS): HR: 0.78; P < 0.0002.
- Specific Cancer Incidence (AHS-2 vs. SEER-NLMS):
- Breast: HR: 0.70; P < 0.0001.
- Colorectal: HR: 0.84; P = 0.035.
- Rectal: HR: 0.50; P < 0.0001.
- Lung: HR: 0.70; P = 0.002.
- Smoking: HR for all subjects, 0.71; 95% CI, 0.67-0.76; P < .0001. HR for black subjects, 0.75; 95% CI, 0.65-0.88; P = .0003.
Other Important Findings
- The black AHS-2 population had significantly lower all-cause mortality and cancer incidence rates compared to the black NLMS population.
- Survival curves showed better survival among Adventists of both racial groups, with black Adventist males showing better survival than white census males.
- The study found a significant reduction in the incidence of all cancers combined and specifically breast, colorectal, rectal, and lung cancers in the AHS-2 population.
- Sensitivity analyses showed that the lower mortality and cancer incidence persisted after removing person-years within the first 2 years of study enrollment.
- The study noted differences in cancer mortality HRs between Adventists and the general population, particularly for prostate and colon cancers.
- Higher education levels were associated with better health outcomes in the Adventist population.
Limitations Noted in the Document
- The study’s findings for cancer comparisons were restricted to SEER states.
- Self-selection bias among Adventists, who may have adopted healthier lifestyles, could influence the results.
- Residual confounding was possible due to factors not fully accounted for in the analyses.
- Misclassification of past smoking habits could have affected the results, especially for lung cancer.
- The power for analyses of specific cancers in the black population was limited due to smaller sample sizes.
- Differences in screening practices, such as prostate cancer screening, could have influenced the results.
- The study acknowledged the possibility of chance influencing the unexpected difference between colon and rectal cancer results due to relatively small numbers.
Conclusion
The study’s primary conclusion is that Adventists, who often adhere to vegetarian diets, exhibit significantly lower rates of all-cause mortality and cancer incidence compared to the general U.S. population. The findings emphasize the potential impact of lifestyle factors, particularly dietary habits, on health outcomes. The significantly lower rates of all-cause mortality and cancer incidence among Adventists, especially breast, colorectal, rectal, and lung cancers, suggest that lifestyle choices, including diet, play a critical role in health outcomes. The fact that cancer mortality HRs were less reduced in Adventists than cancer incidence rates may suggest that cancers particularly affected in Adventists may be at sites less likely to be fatal or that in many sites they are less aggressive variants. The study highlights the importance of lifestyle choices, including diet, on health outcomes and suggests that adopting healthy lifestyles can improve survival and reduce cancer risk. “Lifestyle choices are a likely explanation as these contrasts increase when the Adventists are restricted to vegetarians.” The study also suggests that the adoption of healthy lifestyles at the population level could lengthen life expectancy in this racial group. The authors state, “These results invite speculation that observed survival and mortality differences may be due to lifestyle choices and conferrable to general white and black populations if they were to adopt healthy lifestyles.”
IFFS Team Summary
- Comparison of American 7th Day Adventists to USA General population
- 7th day adventists are mainly plant based, eating low amount of animal products, and many are vegetarian or vegan
- Also have higher education, lower alcohol consumption, amongst other lifestyle factors
- Study controlled for age, race, sex, smoking, and location of residence
- As for any study, could there be over-adjustment, in case of major discrepancies between groups?
- In the case of smoking, instead of only relying on statistical adjustment, the study matched non- smoking subjects in the non adventist population to avoid pitfalls of over adjustment, since smoking is extremely low in the Adventist group
- 7th day adventists are mainly plant based, eating low amount of animal products, and many are vegetarian or vegan
- Also have higher education, lower alcohol consumption, amongst other lifestyle factors
- Study controlled for age, race, sex, smoking, and location of residence
- As for any study, could there be over-adjustment, in case of major discrepancies between groups?
- In the case of smoking, instead of only relying on statistical adjustment, the study matched non- smoking subjects in the non adventist population to avoid pitfalls of over adjustment, since smoking is extremely low in the Adventist group
- HR for all cause mortality was 0.67 at age 65 and 0.78 at age 85 for the Adventist population
- HR for cancer mortality as 0.70 for the Adventist population
- Lower rates of breast, colorectal and lung cancers
- In addition to longer lifespan, there was significantly less premature death in the Adventist group
- Black Adventist males lived longer than white non-Adventist males which is remarkable in the USA
- Lower rates of breast, colorectal and lung cancers
- In addition to longer lifespan, there was significantly less premature death in the Adventist group
- Black Adventist males lived longer than white non-Adventist males which is remarkable in the USA
- Survival curves were a very informative way to present data
- also listed in Total Cancer Section