Family history as a predictor of hospitalization for hypertension in Sweden

OBJECTIVE: Hypertension clusters in families. However, no nationwide study has investigated the family history as a predictor of hospitalization for hypertension, which was the purpose of this study. RESEARCH DESIGN AND METHODS: The study is a nationwide follow-up study. Swedish Multigeneration Register data for individuals aged 0-76 years were linked to Hospital Discharge Register data for 1964-2008. Standardized incidence ratios (SIRs) were calculated for individuals whose relatives were hospitalized with a main diagnosis of hypertension compared with those whose relatives were not. RESULTS: The total number of patients hospitalized with hypertension was 37,686. The familial SIR was 2.18 for individuals with one affected sibling, 44.83 for individuals with two affected siblings and 57.18 for individuals with three or more affected siblings. The SIR was 1.95 for parents with one affected child, 3.73 for parents with two affected children and 9.22 for parents with three or more affected children. The familial SIR among offspring was 1.84 for those with one affected parent and 3.62 for those with two affected parents. The familial risk for hospitalization with hypertension among offspring aged less than 30 years was 2.50 and 1.57 in those aged more than 60 years. Familial risks were similar for men and women. Spouses had low overall familial risks (SIR=1.2). CONCLUSION: Hospitalization for hypertension clusters in families. Very high risks were observed in families with multiple affected siblings, though the parent-offspring transmission was lower, suggesting the segregation of recessive or interacting susceptibility genes. The low familial risk in spouses suggests a minor nongenetic contribution.