Association between blood pressure and mortality in a Spanish cohort of persons aged 65 years or over: a dynamic model.

ABSTRACT

INTRODUCTION AND OBJECTIVES: Few studies have used time-dependent correction to analyze the relationship between blood pressure and all-cause mortality, and to our knowledge none has been performed in older people from the Mediterranean area. This study aimed to estimate the relationship between baseline blood pressure and blood pressure as a time-dependent covariate with the risk of all-cause mortality in a population cohort of persons aged 65 or older in Spain. METHODS: Data were taken from the population-based study "Aging in Leganés" with 17 years of follow-up, launched in 1993 in a random sample (n=1560) of persons aged ≥65 years. Mortality was assessed in 2010. Cox proportional hazards models were fitted to examine the effects on mortality of blood pressure at baseline and of blood pressure as a time-dependent covariate. RESULTS: The lowest mortality was observed at baseline systolic blood pressure of 136 mmHg and time-dependent covariate value of 147 mmHg. The highest risk of mortality for time-dependent covariates occurred with systolic blood pressure <115 mmHg and >93 mmHg and diastolic blood pressure <80 mmHg. Diastolic blood pressure over 85 mmHg did not increase the risk of death. CONCLUSIONS: Based on the dynamic association between blood pressure and mortality, a U-shaped relationship was found for systolic blood pressure and a negative relationship for diastolic blood pressure and all-cause mortality. The lowest mortality corresponded to a systolic blood pressure level slightly over the diagnostic hypertension value and suggests that a value of 140 mmHg is not adequate as a diagnostic and therapeutic threshold in an elderly population.