Dementia Tied to Resting Heart Rate

Higher resting heart rate (RHR) was linked to greater dementia risk and faster cognitive decline independent of cardiovascular disease in a study of more than 2,000 older adults in Sweden.

People with RHR of 80 bpm or higher had a 55% increased risk of developing dementia compared with people whose RHR was 60-69 bpm (adjusted HR 1.55, 95% CI 1.06-2.27), reported Yume Imahori, MD, PhD, of the Karolinska Institutet in Stockholm, and co-authors.

The association remained significant after excluding people with prevalent and incident cardiovascular disease. Cognitive function scores fell over time in all RHR groups, but people with RHR of 80 bpm or higher declined more quickly than people with RHR of 60-69 bpm, Imahori and co-authors wrote in Alzheimer's & Dementia.

Previously, the Atherosclerosis Risk in Communities (ARIC) study showed that an RHR of 80 bpm or more in midlife raised the risk of cognitive decline and incident dementia as people aged.

"Our study showed that this finding was also applicable in RHR measured in late life," Imahori told MedPage Today. "It further revealed that this association was not due to underlying cardiovascular diseases such as atrial fibrillation and heart failure."

"This study is important because RHR might be used to identify older people with a potentially high risk of cognitive decline in a wide variety of settings," Imahori added.

"If cognitive function in patients with elevated RHR is followed carefully and early intervention is made, the onset of dementia might be delayed, which can have a substantial impact on patients' quality of life," she said. "If further studies show that this association is causal, reducing RHR might be considered as a target of intervention."

Imahori and colleagues followed 2,147 older adults (62.1% women) in the Swedish National Aging and Care in Kungsholmen (SNAC-K) population-based study with a mean baseline age about 71. All participants were dementia-free at baseline and followed regularly from 2001-2004 until 2013-2016. Cognition and dementia status were assessed at multiple timepoints. Baseline mean Mini Mental State Examination (MMSE) score was 29.0 and was similar across RHR groups.

Mean RHR, obtained from a standard 12-lead ECG at baseline, was 65.7 bpm. Participants in higher RHR groups were older (mean age about 72), less educated, and were more likely to be current smokers, physically inactive, and hypertensive. Prevalence of cardiovascular disease -- ischemic heart disease, atrial fibrillation, heart failure, or stroke -- at baseline was not significantly different among RHR groups.

Over a median followup of 11.4 years, 289 people were diagnosed with dementia. High RHR remained associated with dementia after excluding people with baseline cardiovascular disease and those who developed cardiovascular disease during followup.

MMSE scores fell faster for people who had high RHR. Compared with a resting rate of 60-69, RHR of 80 or more was associated with annual declines in MMSE score (adjusted β -0.13, 95% CI -0.21 to -0.04); results were similar after excluding prevalent and incident cardiovascular disease. RHR 70-79 also was linked to accelerated drops in MMSE score (adjusted β -0.10, 95% CI -0.17 to -0.04).

The relationship between elevated RHR and cognition might in part reflect pathophysiological pathways independent from vascular risk factors, Imahori and colleagues observed. "Nevertheless, we cannot rule out the possibility that subclinical or undiagnosed cardiovascular diseases may contribute to this association," they wrote.

"This population-based cohort study suggests higher resting heart rate is associated with increased risk for dementia and faster cognitive decline, further adding to the growing body of research showing the health of the heart and brain are closely connected," noted Claire Sexton, DPhil, director of scientific programs and outreach at the Alzheimer's Association in Chicago, who wasn't involved with the research.

"However, this study only shows a correlation between resting heart rate and cognition, not causation," Sexton cautioned. "More research is needed."

Imahori added that caution is needed when generalizing findings to other populations "because our study included mainly Caucasians who had relatively high socioeconomic status."

Unmeasured confounders and selective survival bias might also have influenced associations in the SNAC-K cohort, the researchers acknowledged.

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