[Heart rate variability analysis and neurobehavioral function in community-dwelling older people aged 75 or older].
BACKGROUND: Although heart rate variability (HRV) has been found to be associated with increased mortality in the elderly, the association of HRV and cognitive function and activity of daily living (ADL) capacity in the very elderly are not clear. METHODS: A sample of very elderly people (N = 138), aged 75 years and older, living in Urausu, Hokkaido, participated in this study. Participants were classified into three groups: normal, borderline, and dementia. Time and frequency domain measures of HRV were compared with behavioral and cognitive functions. RESULTS: HRV components, except for the LF/HF ratio, did not correlate with age in the very elderly. The LF component showed a statistically significant correlation with all the variables of behavioral functions. Most HRV components showed statistically significant and positive correlations with the flexibility of the back. The LF and LF/HF ratio were significantly lower in the dementia group than in the normal group. CONCLUSION: Although the meaning of the LF component is still controversial, we foundadefinite relationship between the LF component and behavioral functions. A positive relationship between most HRV components and the flexibility of the back may suggest that reduced flexibility leads to deteriorated cardiopulmonary function and reduced HRV. A further prospective study is needed to examine whether HRV and neurobehavioral functions are independent predictors of morbidity and mortality in very elderly people.