Blood pressure and 10-year mortality risk in the Milan Geriatrics 75+ Cohort Study: role of functional and cognitive status

Background: Optimal blood pressure targets in older adults are controversial.

Objective: to investigate whether the relation of blood pressure with mortality in older adults varies by age, functional and cognitive status.

Design: longitudinal geriatric outpatient cohort.

Setting: Milan Geriatrics 75+ Cohort Study.

Subjects: One thousand five hundred and eighty-seven outpatients aged 75 years and over.

Methods: The relations of systolic (SBP) and diastolic blood pressure (DBP) with mortality risk were analysed using Cox proportional hazards models. Blood pressure, Mini-Mental State Examination (MMSE) and Basic Activities of Daily Living (ADL) were assessed at baseline. All analyses were adjusted for socio-demographic factors, co-morbidities and medications.

Results: One thousand and forty-six patients died during 10-year follow-up. The relationships of SBP and DBP with mortality risk were U-shaped; SBP of 165 mmHg and DBP of 85 mmHg were associated with the lowest mortality. Patients with SBP < 120 mmHg and patients with SBP 120-139 mmHg had 1.64-fold (95% confidence intervals, CI 1.21-2.23) and 1.32-fold (95% CI 1.10-1.60) higher mortality risk than patients with SBP 160-179 mmHg (P values 0.001 and 0.004, respectively). In patients with SBP below 180 mmHg, higher SBP was associated with lower mortality in patients with impaired ADL and MMSE but not in those with preserved ADL and/or MMSE (P for interaction 0.033). Age did not modify the correlation of SBP with mortality.

Conclusions: The correlations of SBP and DBP with mortality were U-shaped. Higher SBP is related to lower mortality in subjects with impaired ADL and MMSE. ADL and MMSE may identify older subjects who benefit from higher blood pressure.