The association between SBP and mortality risk differs with level of cognitive function in very old individuals

Cognitive impairment and dementia are highly prevalent in very old populations. Cardiovascular disease is a common cause of death in people with dementia.This study investigated whether the association of blood pressure (BP) with mortality differed with respect to mini-mental state examination (MMSE) score in a representative sample of very old individuals.

The sample consisted of 1115 participants aged 85, 90, and at least 95 years from the Umeå85+/GErontological Regional DAtabase cohort study. The main outcome was all-cause mortality within 2 years according to BP and MMSE score, using Cox proportional-hazard regression models adjusted for sociodemographic and clinical characteristics associated with death.

Mean age, MMSE score, and SBP and DBP were 89.4 ± 4.6 years, 21.1 ± 7.6, 146.1 ± 23.4 mmHg, and 74.1 ± 11.7 mmHg, respectively. Within 2 years, 293 (26%) participants died. BP was not associated independently with mortality risk, except among participants with MMSE scores of 0-10 among whom mortality risk was increased in association with SBP at least 165 mmHg and 125 mmHg or less, compared with 126-139 mmHg (adjusted hazard ratio 4.54, 95% confidence interval = 1.52-13.60 and hazard ratio 2.23, 95% confidence interval = 1.12-4.45, respectively). In age and sex-adjusted analyses, SBP 125 mmHg or less was associated with increased mortality risk in participants with MMSE scores at least 18.

In people aged at least 85 years, the association of SBP with mortality appears to differ with respect to MMSE score. Very old individuals with very severe cognitive impairment and low or high BP may have increased mortality risk.