Objectives: Sleep-related injury is a serious but under-recognized condition. We examined the occurrence of sleep-related injuries and REM sleep behavior disorder (RSBD) in a community sample of elderly in Hong Kong. Design: A representative sample of elderly aged 70 years or above were interviewed with a screening question on the presence of sleep-related injuries. Those who answered affirmatively as well as a subsample of negative responders were interviewed by clinicians. Patients with suspected sleep disorders underwent physical and psychiatric assessment as well as sleep studies. Setting: NA Patients or Participants: NA Interventions: NA Results: In total, 1034 elderly were surveyed and 0.8% reported history of sleep-related injury. Four subjects were confirmed to have RSBD, giving an estimated prevalence of RSBD of 0.38% (95% CI=0.01 to 0.76%). One subject had suspected RSBD but refused investigations while 1 had history suggestive of transient RSBD but could not be confirmed by the sleep studies. The course of RSBD in these subjects was that of a waxing and waning course instead of a progressive deterioration as described in previous literature. Two patients had been hospitalized for sleep-related injury before but their sleep disorder was not recognized. Conclusions: We found that sleep-related injury and RSBD were not rare in the elderly but were frequently under-recognized. Our study calls for greater attention to elderly who had sustained injury during sleep.

The lattice parameter, bulk modulus, cohesive energy, and magnetization of Fe, Co, and Ni are calculated using the generalized gradient approximation (GGA) of Perdew and co-workers. The GGA results agree better with experimental data than the corresponding results calculated with the local-spin-density approximation (LSDA). In particular, the overestimation of the cohesive energies are reduced and the GGA correctly predicts the bcc ferromagnetic phase to be the ground state of Fe, while the LSDA fails to do so. We have also studied the electronic and magnetic properties of the insulating antiferromagnetic transition-metal compounds FeO, CoO, and NiO with the GGA. For these oxides it is found that the results are very similar to the results calculated with use of the LSDA.

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