Introduction: Studies examining the association between heart rate variability (HRV) and cognition are few and report conflicting results. Paced breathing during HRV protocols controls for respiratory sinus arrhythmia, which alters HRV parameters. We investigate for the first time the association between cognitive performance and HRV recorded during different breathing protocols, in a large nationally representative population study of older adults.
Method: Cross-sectional analysis of wave 1 data from the Irish Longitudinal Study on Ageing (TILDA) was performed. TILDA is a prospective cohort study of community-dwelling adults aged 50 years and older. A subset of 4,763 participants who underwent 10 min electrocardiogram (ECG) recording during resting and paced (0.2 Hz) breathing were analysed. Time and frequency domain HRV indices were divided into quintiles and cognitive performance was defined using the Montreal cognitive assessment (MOCA) score. Multivariate linear regression was used to model the association between HRV and cognition, adjusting for demographics, clinical profile, mental health, cardiovascular disease and medications.
Results: The mean age was 61.7 years and 2,618 (55%) were female. Lower quintiles of standard deviation of NN intervals (SDNN) (P < 0.001 resting; P < 0.01 paced), low frequency (P < 0.001 resting; P = 0.001 paced), and low frequency: high frequency ratio (P < 0.001 resting; P = 0.049 -paced) were significantly associated with lower MOCA scores (during both recording periods), independent of confounders. Subdomains of MOCA responsible for the association were predominantly memory recall and language.
Conclusion: Reduced HRV is associated with poorer cognitive performance. Reduced HRV may be associated with reduced baroreflex sensitivity or central autonomic dysfunction which may lead to or be caused by cerebral hypoperfusion. Hypoperfused states are associated with both white matter lesions and cognitive impairment. Inflammatory markers are elevated in states of reduced HRV and cognitive disorders, suggesting involvement of the immune system. The causality of the relationship between autonomic dysfunction and cognitive disorders warrants further investigation.