Cardiac autonomic modulation and cognitive status in Alzheimer's disease

Although nervous structures affected in Alzheimer's disease are also implicated in autonomic nervous system function, the relationship between autonomic and cognitive functions was not still investigated. The cardiac autonomic modulation of 5-min heart interval variability evaluated by time- and frequency-domain indexes, in supine and standing positions, of 22 Alzheimer's disease patients (90.9% women) aged 79.6 +/- A 1.4 years (mean +/- A SE) was correlated with mild to severe cognitive impairment scored by the CAMCOG and MMSE subset tests, by the Spearman's correlation analysis. Age and level of education were not correlated with the heart interval variability indexes and the cognitive scores. Significantly positive (r (s) = 0.43-0.47, P = 0.03-0.04) or trend (r (s) = 0.36-0.40, P = 0.06-0.10) correlation was observed in both positions between the cognitive performance and pNN50%, rMSSD and absolute and normalised high-frequency power, considered to express parasympathetic modulation. Negative trend correlation (r (s) = -0.35 to -0.39, P = 0.07-0.10) was observed between absolute sympathetic modulation (low-frequency power and low-to-high frequency power ratio) in supine posture. The cognitive status and the cardiac sympathovagal modulation appear to be correlated and hypothetically may influence one another in mild to severe Alzheimer's disease. Individuals with more severe cognitive deficiency showed suggestive lower cardiac parasympathetic modulation and trend for higher cardiac sympathetic modulation.