Sleep and Obesity- Understanding the Interactions and Consequences

Sleep Quantity- Partial sleep deprivation is the most common form of sleep deprivation in today's lifestyle. This sleep disorder is said to occur when one fails to obtain a usual amount of sleep. A conscious decision is made to sacrifice sleep to complete other tasks. Exposing eyes to bright light (computers, mobile phone,TV) further delays sleep onset. This activity can become chronic. In a study by National Sleep Foundation 15% of subjects aged between 18-44 years reported sleeping less than 6 hours on weekdays and 10% reported sleeping less than 6 hours on weekends over the past year. ¹

Hasler et al have demonstrated that chronically reduced sleep times are associated with obesity. ² This prospective study showed an association between short sleep duration and obesity and a negative association between sleep duration and body mass index in young adults. Kobayashi Daiki et al have demonstrated that short sleep (<5hours) is significantly associated with weight gain and obesity in both males and females.³ Sleep is an important modulator of neuroendocrine function and glucose metabolism. Sleep loss has been shown to result in metabolic and endocrine alterations. These include decreased glucose tolerance, decreased insulin sensitivity, increased evening concentrations of cortisol, increased levels of ghrelin, decreased levels of leptin. Increased ghrelin causes increased hunger and appetite.

Sleep Quality – There are several sleep disorders. Obstructive sleep apnea syndrome (OSAS) is common disorder. OSAS is strongly associated with obesity but is also increasingly identified in the less obese, in whom a the particular craniofacial structure is an important contributory factor. ⁴ Adult obese subjects can have normal body weight during childhood and become obese later. The presence of narrow upper airway since childhood may cause obstructive sleep apnea in younger age. Chief nocturnal events in obstructive sleep apnea include cyclical hypoxia and cyclical sympathetic stimulation. Recurrent stimulation of sympathetic system results in metabolic aberrations which subsequently can cause obesity. Nocturnal events in OSA are recurrent, night after night (whenever the patient goes to sleep). It is not uncommon for patients of OSA to sleep in daytime also.

Obesity causes OSA or OSA causes obesity?

In an obese OSA patient it is often assumed that obesity has caused OSA but it is possible that OSA has built up the body mass index due to nocturnal events mentioned. Once obesity is established, it is blamed for the development of OSA which may not be true. This phenomenon of chicken and egg story in relation to obesity has been discussed by Pillar G et al. ⁵ Obese subjects who undergo bariatric surgery need to undergo polysomnography to rule out the presence of OSA. The presence of narrow upper airway can result in a recurrence of obesity. It must be appreciated chronic partial sleep deprivation can lead to snoring due to hypotonia of pharyngeal muscles.⁶ Increase in ghrelin is noted in OSA patients causing increased appetite and binge eating. This also promotes weight gain. Daytime sleepiness in OSAS also promotes obesity.

Therefore, it is essential to recognize sleep problems while evaluating and treating obesity and associated metabolic disorders like Type 2 diabetes mellitus.⁷

References:

1. 2002.Sleep in America Poll-National Sleep Foundation Washington DC 2002

2. Hasler G, Busysee DJ, Klaghofer R etal. The association between short sleep duration and obesity in young adults : 13 year prospective study sleep 2004 ; 27 ( 4 ) : 661 – 6

3. Kobayashi D,Takahashi O, Desphande GA,Shibo T, Fukui T. Association between weight gain , obesity and sleep duration: a large scale 3 year cohort study. Sleep Breath 2012;16(3): 829-33.,

4. Gibson GJ. Obstructive sleep apnoea syndrome: underestimated and undertreated. British Medical Bulletin 2004; 72: 49-64.

5. Pillar G, Shehadeh N.Abdominal Fat and Sleep Apnea;the chicken or the egg? Diabetes Care 2008;31(Suppl 2):S303-S309.

6. Leither JC, Knuth SL, Barlett D Jr. The effect of sleep deprivation on activity of genioglossus muscle. Am Rev Respir Dis 1985;132:1242-5

7. Iyer SR, Iyer Revati R, Bhagyalakshmi V,. Avoiding Type 2 Diabetes Express Highway from Infancy to Old age-Focus on newer risk factors. J Assoc Physicians India 2019; 67: 68-72