“…However, increasing evidence from prospective studies shows that disrupted sleep and short sleep duration (under 6.5 hours) are implicated in higher levels of diabetes, obesity, hypertension and mortality (Ayas, White, Al-Delaimy, Manson, Stamfer, Speizer et al, 2003;Ferrie, Shipley, Cappuccio, Brunner, Miller, Kumari et al, 2007;Gangwisch, Heymsfield, Boden-Albala, Buijs, Kreier, Pickering et al, 2007;Patel, Ayas, Malhotra et al, 2004;Tamakoshi & Ohno, 2004;Yaggi, Araujo & McKinlay, 2006). Experimental laboratory research has also shown that chronic sleep deprivation (restricted to 4 hours of sleep for 6 nights) results in significant changes in carbohydrate metabolism, decreased glucose tolerance, elevated evening cortisol levels and increased sympathetic activity, indicating that sleep loss can increase 'allostatic load', facilitating the development of chronic conditions, such as obesity, diabetes and hypertension .…”