• James A Greenberg.
• Department of Health and Nutrition Sciences, Brooklyn College of the City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA. jamesg@brooklyn.cuny.edu
• J. Hypertens. 2003 Jan 1; 21 (1): 49-56.

ObjectiveTo assess the relationship between mortality risk and systolic blood pressure (SBP) at low and moderately increased SBP (less than the 70th percentile) before and after correcting for the regression-dilution bias and J-curve effects.DesignCohort study.SettingThe First National Health and Nutrition Examination Survey Epidemiologic Follow-Up Study.ParticipantsThe 6839 individuals who participated in the 1982-1984 survey for whom there were no missing data (age range 34-87 years).Main Outcome MeasureCardiovascular disease mortality (n = 678) during a 9-year follow-up.MethodsCorrections were made for the regression-dilution bias by using average SBP during the decade before baseline as the mortality predictor, and for J-curve effects by excluding individuals who exhibited high age-stratified mortality rates and a decrease in SBP. Cox's regression was used to analyse the follow-up relationship between mortality risk and SBP.ResultsThe corrected relative cardiovascular disease mortality risk was 1.23 (95% confidence interval (CI), 1.16 to 1.31) for a 10 mmHg increase in SBP. The relationship was monotonically positive starting at the lowest SBP category in the analysis (< 115 mmHg), and robustly so above about the 32nd percentile (120 mmHg). The equivalent uncorrected result was 1.08 (95% CI, 1.05 to 1.13), and the relationship was J-shaped and became positive above about the 68th percentile (135 mmHg). Below the 70th percentile of SBP, individuals in the corrected analysis were 89% of all individuals.ConclusionThese two corrections transformed the relationship between mortality risk and SBP at low and moderately increased SBP from no association to a robustly positive association starting at 120 mmHg, for the majority of individuals.

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