A cohort is a defined population observed over time, either prospectively or retrospectively. In some cohorts, members share a characteristic such as an occupational exposure or medical condition, while some other cohorts are samples of the general population. In addition, some DCEG cohorts were first enrolled in clinical or prevention trials, but continue to be followed as a general population cohort.
Cohort members are often surveyed to gather information on lifestyle factors such as diet and nutrition, exercise, use of alcohol or tobacco, because these factors can be related to cancer risk. They are followed over time to gather updates on their general health. In addition, in some studies, members agree to donate biospecimens such as blood, buccal cell, and urine.
For cancer studies that require large numbers of subjects and biospecimens, DCEG investigators often participate in large consortia (collaborative partnerships) that pool data and biospecimens across numerous cohorts. For example, the NCI Cohort Consortium includes investigators responsible for more than 40 high-quality cohorts, involving more than 4 million people.
Following are examples of DCEG cohort studies:
Thyroid Disease in Young Persons Exposed Near Chernobyl
Thyroid Disease in Young Persons Exposed Near the Kazakhstan Semipalatinsk Nuclear Test Site
Study of People Exposed to Radioactive Waste Near the Techa River in Russia
HPV Vaccine Study in Costa Rica
DES Follow-up Study
Childhood Cancer Survivors
Nutritional Intervention Trials in Linxian, China
Second Primary Gastrointestinal Cancers
Study of Women with Augmentation Mammoplasty
Study of Women Evaluated and Treated for Infertility
Follow-up Study of Women in the Fracture Intervention Trial