A retrospective study of 124 non-demented elderly people (aged 65-88.5 years) complaining of sleep disturbances and meeting the criteria of exclusion was made. The participants were admitted to a sleep medicine center laboratory in Taiwan and underwent a nocturnal polysomnography (PSG) from 1 January 2002 to 31 January 2003. The data of 1014 controls originated from 15 798 individuals were compared without a PSG. The assessment included changes in the sleep homeostat: total sleep time (TST), insomnia, snoring, apnea-hypopnea, sleep efficiency and a probability based evaluation of sleep variables. A comparison between the current study and other published reports was made. Other discussions included the role of suprachiasmatic nucleus (SCN) and its effect on sleep apnea, the apolipoprotein epsilon 4 genotype status, the effect of sleep apnea on various TST, the different TST above and below the median and long sleep time. Low snoring and a high apnea-hypopnea index and the significance of central type sleep apnea were evaluated. Although vasopressin-positive and vasoactive-intestinal-polypeptide neurons were not measured postmortem, as there was no death case, the focus was on the analyzing sleep disturbances that could be interpreted as the result of an altered SCN function. Evidence was presented for a reduction of the circadian rhythm, which leads to the impairment of sleep consolidation. The function of SCN regresses with age and diminishes more with advanced age. Given all the other possibilities of things going wrong in aging, it is significant that sleep disturbances are in the forefront.

The story of a race to unlock the Holy Grail of biology is a fascinating and an exciting one. It appears to be an impossible task to predict the final outcome of the quest while there are so much left to play for, but undoubtedly, the swift advances in decoding the human genome and the tools available to decipher the genetic information will likely forever alter the practice of medicine. It will definitely affect anyone on this planet that have access to modern health care and will subsequently improve the condition of the entire human race.

In the article by Escudero et al (2006), there are only random samples, which are useful for the validity of the study design. In this author's opinion, there are still other clinicophysiological characteristics that merit consideration and scrutiny as discussed below. The hypothesis set by the original authors needs to be adequately justified. Their hypothesis appears to be that the multiscale entropy (MSE) is positively related to a non-linear analysis of an electroencephalogram on patients with Alzheimer's disease.

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