In the early 1980s, a review of existing data by the Subcommittee on Cardiovascular and Cerebrovascular Disease of the Secretary of Health and Human Service’s Task Force on Black and Minority Health concluded that information on cardiovascular disease (CVD) in American Indians was inadequate and strongly recommended epidemiologic studies of this problem. The Strong Heart Study (SHS) was designed to respond to this recommendation.
In its initial stages, the SHS included three components. The first was a survey to determine cardiovascular disease mortality rates from 1984 to 1994 among tribal members aged 35-74 years of age residing in the 3 study areas (the community mortality study). The second was the clinical examination of 4,500 eligible tribal members. The third component is the morbidity and mortality (M&M) surveillance of these 4,500 participants. The SHS has completed three clinical examinations of the original Cohort Phase I: 1989-1991; Phase II: 1993-1995; 1998-1999, respectively. Due to the importance of genetics in the occurrence of CVD, the SHS expanded into the genetic epidemiology area. In the Phase III study, in addition to the Cohort examination, the study conducted a pilot family study. The family pilot study recruited approximately 30 families (10 per field center) which consisted of more than 900 family members. Due to the success of the pilot study, was funded to conduct a full-blown family study, the Strong Heart Family Study (SHFS) to investigate the genetic contributions to CVD and its risk factors. Phase IV genetic studies emphasized genetic linkage analysis to localize genes that contribute to CVD risk. In Phase IV, an additional 18 to 25 extended families (a total of about 900 members at least 15 years of age) were recruited from each of the field centers from 2001 – 2003. This provides a total of 3,776 individuals from 94 families, of whom 825 are Phase III participants re-examined in Phase IV.
In Phase V, genetic studies emphasized the investigation of selected candidate genes and follow-up of localized genetic risk factors. Mortality and morbidity surveillance of the original cohort (2859 male and female survivors, ages 60 – 89 years) continued and family members were re-examined. of the SHS focuses on the continuation and expansion of the mortality and morbidity surveillance of the original cohort (n=4,549) and the family cohort (n=3,776) that were recruited during Phase I and Phase IV, respectively.
Phase VI continued the mortality and morbidity surveillance of the original SHS cohort and of the SHFS participants to better understand cardiovascular disease, cancer, liver disease, and inflammation in American Indians. All surviving participants were invited to participate in Phase VI and fill out a medical history questionnaire after a written consent is given. Their medical records were then reviewed and pertinent information is abstracted for morbidity and mortality events that were suspected to relate to the diseases of interest. The abstracted information was reviewed by physicians on the Morbidity and Mortality Review Committees to determine whether the event is related to cardiovascular disease, cancer, liver disease, etc. Incidence rates and prevalence proportions of these health conditions as well as their risk factors, including genetic factors, were determined from analyses of the data collected in Phase VI and those collected in Phases I-V
Phase VII is currently underway. The NHLBI has issued contract awards to support the Strong Heart Study (SHS) infrastructure and continued surveillance during a Phase VII (beginning February, 2019 for a seven-year duration). Support for a basic follow-up examination of approximately 3,500 participants during the contract cycle will be included. The SHS Phase VII exam will serve as a platform for in-depth ancillary studies that are funded outside of the SHS contracts. These ancillary studies will be operationally integrated into the main study, and can propose additional exam components.