In Western, industrialised societies, it is conventional for non-shift-workers to remain awake and eat during the day whilst sleeping and not eating during the night. Babies probably learn this pattern of behaviour. However, as a baby, feeding and going back to sleep quickly is initially regarded as very acceptable, nocturnal behaviour. The International Classification of Sleep Disorders lists approximately 80 sleep disorders. Three of the main divisions are dyssomnias (disturbed sleep), parasomnias (undesirable behaviours that occur during sleep), and sleep disordered by other medical or psychiatric disorders. The dyssomnias are further subdivided into: a) intrinsic (disturbed sleep-wake control), b) extrinsic (external or developmental) and c) circadian (biological clock).
Nocturnal eating (drinking) syndrome is regarded as extrinsic sleep disorder. However, within the classification, this is regarded mainly as a developmental sleep disorder if it continues beyond 6 months. The estimated prevalence is about 5% from ages ranging from 6 months to 3 years.
Sleep-walking and night-terrors are among the better known examples of a parasomnia. Sleep-walking takes place out of deep sleep and is characterised by amnesia and difficulty in waking the afflicted. Prevalence estimates vary widely, from between 1-15% of the population, but it seems mainly be a childhood disorder � but it may not be. It is not regarded as pathological, but a sleep-walker can accidentally harm themselves or others. It is not harmful to try to awaken the sleeper and it is not surprising if it takes many minutes for them to come to their senses. They can if possible be guided back to their bed to sleep. Sleepwalkers usually do not remember their perambulations.
Night-eating syndrome is found in approximately 10% of obese individuals. Individuals eat little or no food in the morning but consume increasing quantities in the evening. Food intake during the night is associated with insomnia. In contrast, binge-eating disorder involves the large consumption of food in one sitting with a subjective sense of loss of control.
Night-eating syndrome was first described in 1955 (Stunkard et al., 1955) . It is characterised by morning anorexia (not eating in the morning), evening hyperphagia (eating a lot in the evening, or during the night) and insomnia. Its estimated prevalence is 1.5% of the general population and between 10-26% in obese patients ( (Birketvedt et al., 1999) .
Whilst there is a debate whether night eating disorders are eating disorders or sleep disorders it has become clear that investigating the sleep characteristics is worthwhile. The following sleep disorders have been found in individuals who have been investigated in a sleep laboratory or sleep disorders centre:
� Sleep walking
� Periodic Limb Movement (PLM)
� Triazolam abuse
� Obstructive Sleep Apnoea (OSA)
� Irregular sleep/wake pattern disorder
� Familial restless legs syndrome
� Amitriptyline treatment of migraine
(Manni et al., 1997; Schenck et al., 1993; Schenck and Mahowald, 1994; Schenck and Mahowald, 2000; Winkelman, 1998; Winkelman et al., 1999)
Onset of sleep-related eating is closely linked with 1) acute stress involving reality-based concerns, 2) abstinence from alcohol or opiate/cocaine abuse, 3) cessation of cigarette smoking.
Eating Adult helpline +44 01603 621414 mon-fri 9am-6:30pm. youth helpline (under 18s) +44 01603 765050 mon-fri 4pm-6pm outside those hours if young people leave a message the youth helpline will call you back.
Sleep If you would like to talk to anyone with a sleep-related disorder, a help line run by the Medical Advisory Service can be reached on +44 0208 994 9874 (19.00-21.00 GMT).
No specific web sites have been set up. This directory lists most of the useful sleep sites on the web.
Manni,
R., Ratti, M.T., and Tartara, A. (1997) Nocturnal eating: prevalence and
features in 120 insomniac referrals. Sleep
20, 734-738.
Schenck,
C.H., Hurwitz, T.D., O'Connor, K.A., and Mahowald, M.W. (1993) Additional
categories of sleep-related eating disorders and the current status of
treatment. Sleep 16,
457-466.
Schenck,
C.H. and Mahowald, M.W. (1994) Review of nocturnal sleep-related eating
disorders. Int J Eat Disord 15,
343-356.
Schenck,
C.H. and Mahowald, M.W. (2000) Parasomnias. Managing bizarre sleep-related
behavior disorders. Postgrad Med
107, 145-156.
Stunkard,
A.J., Grace, W.J., and Wolff, H.G. (1955) The night-eating syndrome. A pattern
of food intake among certain obese patients.
Am J Medicine 19, 78-86.
Winkelman,
J.W. (1998) Clinical and polysomnographic features of sleep-related eating
disorder. J Clin Psychiatry 59,
14-19.
Winkelman,
J.W., Herzog, D.B., and Fava, M. (1999) The prevalence of sleep-related eating
disorder in psychiatric and non-psychiatric populations.
Psychol Med 29, 1461-1466.
Written by Chris Idzikowski
6 Feb 2001