The problem of elderly is, that with the forthgoing biological age, an elderly person becomes more and more individual concerning his/her medical as well as personal history. In other words, within a collective of elderly, there is more and more intra-individual variability especially with the growing age. This will concen probably many different aspects. Moreover, seasonal variations concerning mobility, activity, nutritional status etc.in elderly play more significant role then in young people. 

Thus, it will be difficult to compare to circadian rythms of "aged" with "young"  

In older adults the variability of life style invites us to control the healthy, habits and life story. Dissociation of epigenetic and intrinsic changes remains difficulty. If you want to describe “changes” you need to develop a longitudinal study. But how it is expansive you can define the groups of children, young adults and older adults, controlled healthy and other variables that interested to you.

I found some articles that can help you:

http://www.ncbi.nlm.nih.gov/pubmed/25033025

http://www.ncbi.nlm.nih.gov/pubmed/24588832

Hi there,

please refer some of my publications:

https://www.researchgate.net/publication/258201778_Aging_and_circadian_rhythms_general_trends

http://www.ncbi.nlm.nih.gov/pubmed/16183237

http://www.ncbi.nlm.nih.gov/pubmed/12067601

Dr. Karasek:

http://www.jpp.krakow.pl/journal/archive/12_07_s6/pdf/105_12_07_s6_article.pdf

Chapter Aging and circadian rhythms: General trends

The best explanation I find is that circadian rhythms are the expression of a multioscilatory system and changes in amplitude (notably attenuation in the elderly) would thus result from uncoupling of oscillators, a situation that occurs in younger individuals when they are sick. Age per se should not be considered as a causal agent as it has become usual in some literature on the "effects of aging". 

Behavior of your subjects will be very important. If an individual spends the day-time outdoors in 100,000 lux light and has a relatively dark bedroom, light-regulated processes such as the melatonin axis, will receive a high-amplitude external cues. If they spend most of the day indoors (

Thanks everyone. Having a look on the publications. Will post specific queries soon.

Here is a paper that I contributed to: . D. F. Kripke, S. D. Youngstedt, J. A. Elliott, A. Tuunainen, K. M. Rex, R. L. Hauger, and M.R. Marler, Circadian phase in adults of contrasting ages, Chronobiology International, 22L 695-710, 2005.

Professor Kripke probably has some more publications since then that you can find.

Here is another, with an extreme of age: Martin JL, Marler MR, Harker JO, Josephson KR, Alessi CA. A multicomponent nonpharmacological intervention improves activity rhythms among nursing home residents with disrupted sleep/wake patterns. Journals of Gerontology; Medical Sciences. In press 2006.

I think that professor Martin has more research since that one that you can find.

Many variables change their circadian characteristics with age. In many cases, including melatonin, the circadian amplitude decreases. In variables such as blood pressure and heart rate, the variability in the circadian acrophase increases. The circadian waveform can also undergo changes: for instance, in blood pressure, the second harmonic with a period of 12 hours increases in prominence with advancing age, resulting in a more pronounced post-prandial dip in the elderly. Other changes are also taking place, such as an increase in the relative prominence of the biologic week versus the circadian variation, seen for blood pressure and heart rate.

Thanks Germaine the relevant answer. Now, I understand that the evolution of the circadian waveforms with age is process dependent. Can, you tell me some references where such variations for sleep related wave forms are dealt with? 

There is a team at the VTT Technical Research Centre of Finland (Juho Merilahti, Ilkka Korhonen) who did actigraphy longitudinally in the elderly. There may be some interesting information regarding sleep patterns in older people from their publications.