The Adventist Health Study, a cohort investigation which began in 1974, had some very basic differences from the earlier mortality studies, in that it:
- Was designed to find out which components of the Adventist lifestyle give protection against disease. Unlike the previous studies, it did not aim to compare the rates of disease or mortality between Adventists and non-Adventists.
- Included the addition of data reporting both fatal and nonfatal disease events. Added a more detailed investigation of diet.
- In the beginning, the Adventist Health Study-1 was primarily a cancer investigation. In 1981, the cardiovascular component was added.
Conducting the Study
Initially, 63,530 census questionnaires were mailed to every Adventist household in California. The goal was to enroll every adult in these households over age 25.
Two years later, a more extensive lifestyle questionnaire was sent to those who had responded to the census questionnaire. This questionnaire included:
- Previous medical history questions
- Previous drug therapy questions
- More than 60 dietary questions
- A variety of psychosocial questions
- Questions about physical activity
The response rate from white non-Hispanic subjects was the highest of any ethnic group, with 34,198 individuals responding from that group.
Collecting Event Data
Researchers followed this group closely for the next six years, looking for both fatal and nonfatal cases of either cancer or heart disease. An annual questionnaire was mailed to each individual, asking about any hospitalization within the previous 12 months.
Subsequently, a field staff of Adventist Health Study researchers was dispatched to visit the medical records departments of the hospitals mentioned by the subjects. The field staff reviewed all hospital records of each admission, looking for any hint of cancer or coronary heart disease events. For suspected acute coronary heart disease events, copies of physician records, electrocardiograms and abstractions of serum enzyme reports were obtained. For suspected cancer cases, copies of histology and other relevant tests were taken.
To find fatal cases of cancer or heart disease with deaths taking place outside the hospital, researchers used several means:
Obtaining the deceased person’s annual questionnaires from consenting relatives. Obtaining church records. Comparing these records to state death records for California. Using the National Death Index to track deaths for those who had moved away from California.
Diagnosing a new cancer event required a histological confirmation of a malignant tumor sometime after the subject had already entered the study. Confirming a new case of acute myocardial infarction or fatal coronary heart disease was made by applying published international diagnostic criteria for these events.
Great effort was made to establish the validity and accuracy of the questionnaire information initially gathered. When compared to the information gained from face-to-face interviews, the data obtained through the questionnaire and follow-up was remarkably accurate. Missing data occurred in between one and seven percent of the responses for different variables. Interestingly, the rate for missing data did not increase for questions that might be sensitive to Adventists, such as alcohol consumption, eating pork and other meats, or drinking coffee.
Data Revelations and Response Rate
When gathering follow-up data was officially concluded, 32,000 hospitalizations were reported, representing 28,000 hospital charts on 18,053 different individuals. In California, 698 different hospitals were involved, and 960 hospitals out-of-state.
Normally, researchers are pleased when they receive a response rate of 50 percent. For the annual follow-up questionnaires containing this critical hospitalization data, response rates were in excess of 90 percent. The final follow-up questionnaire received an incredible 99.5 percent response.
In the decade since the last of the formal data collection, Adventist Health Study researchers have looked at the data from a variety of angles. What follows are some of the exciting discoveries that prove beyond a doubt the ways in which certain aspects of the Adventist lifestyle have improved the health of participants.