Polygraphic sleep criteria as predictors of successful aging: an exploratory longitudinal study

Background: A cohort of 57 elderly healthy volunteers (34 male, 23 female) was studied in a sleep laboratory on four consecutive nights when their average age was 63.5 ± 3.7 years. Thirty subjects (20 male, 10 female) were assessed 14 years later; 21 had either died in the meantime or were very ill, and 6 did not participate for other reasons. Methods: Two operationalizations of successful aging were applied: survival in relatively good health (30 survivors vs. 21 nonsurvivors), and cognitive competence as assessed in the survivors by means of tests of cognitive function. Results: Whereas none of the sleep characteristics determined at baseline distinguished the survivors from the nonsurvivors, several parameters [REM (rapid eye movement) sleep latency, REM density, and NREM (non-REM) shifts] were significantly correlated with one or more measures of cognitive functioning at follow-up. These polygraphic sleep parameters also distinguished a subgroup of cognitively fully competent subjects from those who, according to their performance in tests of cognitive function, could be considered as mildly demented. Conclusions: While the REM latency and density findings support the theory of a functional link between brain cholinergic activity, timing, and density of REM sleep and cognitive functioning, the positive association between the number of NREM shifts at baseline and cognitive performance 14 years later is difficult to explain. It is suggested that the findings of the present study, in particular the potential predictive value of REM latency and REM density for cognitive functioning in the old, need replication in other subject samples followed for similar time periods.