BP variability signals development of dementia in elderly
Older adults with increased day-to-day blood pressure (BP) variability may be at greater risk of developing all-cause dementia, vascular dementia (VaD) and Alzheimer’s disease (AD), according to a Japanese cohort study.
“[F]indings of this study indicate that the measurement of day-to-day BP variability with home BP monitoring may be useful to assess future risk of dementia, regardless of its subtype,” the investigators said.
The investigators followed 1,674 community-dwelling Japanese elderly without dementia for 5 years, with home BP measured three times every morning for a median of 28 days. Day-to-day systolic (S)BP and diastolic (D)BP variabilities were calculated as coefficients of variation (CoV) of home SBP and DBP.
Of the study participants, 194 individuals developed all-cause dementia, including 47 with VaD and 134 with AD, during follow-up. Cox proportional hazards model revealed that the age- and sex-adjusted incidences of all-cause dementia, VaD and AD significantly increased with greater CoV levels of home SBP (p<0.05 for trend). All associations persisted despite controlling for potential confounders. [Circulation 2017;136:516-525]
The risks of developing all-cause dementia, VaD and AD were particularly greater among individuals in the highest quartile of CoV levels of home SBP than among those in the lowest quartile. The corresponding hazard ratios (HRs) were 2.27 (95 percent CI, 1.45 to 3.55; p<0.001), 2.79 (1.04 to 7.51; p=0.03) and 2.22 (1.31 to 3.75; p<0.001).
A similar pattern of associations was seen for CoV levels of home DBP.
When the combined influences of home SBP levels and CoV levels of home SBP on the risk of VaD and AD were estimated, the investigators noted that “both higher day-to-day BP variability and hypertension were independently associated with the risk of VaD, whereas the risk of AD was increased significantly in [individuals] with higher BP variability regardless of absolute BP values.”
The investigators explained that, based on available evidences, “BP variability may be a causative factor of the alterations in brain structure and function, which in turn might lead to the development of dementia, especially VaD. On the other hand, [the variability] may be a marker of neurodegeneration, which has specific findings in AD, although the exact mechanisms responsible for these associations are unclear.”
Despite the presence of several limitations, the present data demonstrate the potential utility of measuring day-to-day BP variability on a home BP basis in assessing future risk of dementia and elucidating BP–related pathological processes in each dementia subtype, the investigators pointed out.
“However, further investigations are required to clarify whether day-to-day BPV is an indicator of future dementia or an interventional target for the prevention of dementia,” they said.
In a companion piece, Drs Alexander Merkler and Costantino Iadecola from the Weill Cornell Medical College in New York stressed that the current study contributes considerable strength to the association between higher BP variability and dementia. [Circulation 2017;136:526-528]
“If confirmed in a larger cohort, [the present] findings may guide future prospective studies aimed at curtailing the risk of dementia by reducing BP variability,” they said.