J.X. and Circadian Rythum

During my recitation sections this week, students raised interesting questions regarding the case study of J.X., presented to our class in lecture on Monday (Miles et al., 1977).  If you wish to read the original article, Rutgers' students may access it through JSTOR.

Here are the results from research (Sack et al., 2007) into the topic, with respect to (some) of my students' questions:

• Yes, circadian rhythm sleep disorders (CRSDs), may change as a person ages.  
• No, CRSDs do not only affect the blind, but the free-running disorder is common in people who are totally blind.  It should be noted that for humans and many other organisms, sunlight is the most important circadian cue.
• Research suggests that gender may affect susceptibility to, and severity of certain CRSDs.
• Recent genetic research has linked "clock gene" mutations to families exhibiting a predisposition to CRSDs (i.e., heritable trait).  

For reference, a "normal" circadian cycle (Image source: Wikimedia Commons)

Works cited (Note: Students, do not follow this blog's citation formatting):

Miles, L. E. M.,  Raynal, D. M.,  Wilson, M. A.  1977.  Blind Man Living in Normal Society Has Circadian Rhythms of 24.9 Hours.  Science 198: 421-423.

Sack, R., Auckley, D., Auger, R.R., Carskadon, M.A., Wright, K.P., Vitiello, M.V., Zhdanova, I.V.  2007.  Circadian rhythm sleep disorders: Part II, advanced sleep phase disorder, delayed sleep phase disorder, free-running disorder, and irregular sleep-wake rhythm. SLEEP 30(11): 1484-1501.