Obesity and lack of physical activity are well established as risk factors for type 2 diabetes (Jeon et al, 2007; Abdullah et al, 2010), which are commonly incorporated into screening instruments, such as FINDRISC, to estimate diabetes risk (Lindström and Tuomilehto, 2003). There is clear and convincing evidence from a number of large, long-term randomised controlled trials that lifestyle intervention incorporating weight loss and increased physical activity are effective at reducing incidence of diabetes in those with impaired glucose regulation (IGR; Gill and Cooper, 2008). However, a substantial proportion of individuals do still progress to diabetes despite the undergoing current gold-standard lifestyle interventions, and there is scope for cost-effective refinement of screening instruments to better identify those at increased diabetes risk. Thus, identification of other easily measurable and potentially modifiable diabetes risk factors could potentially help inform future risk screening and diabetes prevention strategies. Evidence from recent prospective studies, suggests that two such factors may be strength and sleep.
In a report from Li and colleagues (summarised alongside), 133353 women without diabetes from the Nurses’ Health Study and the Nurses’ Health Study II were asked how much difficultly they had in falling asleep and staying asleep over the previous 4 weeks, their sleep duration and how frequently they snored. There were 6407 cases of incident diabetes over 10 years of follow-up. Women with sleep difficulty had a 45% increased risk of diabetes. Almost half of this excess risk was mediated by obesity, hypertension and depression, but even after adjustment for these factors (and a comprehensive range of other confounders) difficulty in sleeping was associated with a 22% increase in type 2 diabetes risk. Other studies have highlighted the association between short sleep duration and diabetes risk (Cappuccio et al, 2010); this study makes an important further contribution to the evidence base that sleep-related variables may make a more important contribution to diabetes risk than is often recognised.
In another report, coincidentally by Li and colleagues (I assume no relation; summarised on the following page), 1682 men in the MAILES (Men Androgen Inflammation Lifestyle Environment and Stress) study had body composition measured by dual-energy X-ray absorptiometry (DXA) and grip strength measured using a hand grip dynamometer. They were followed up for 5 years, during which time 146 men developed type 2 diabetes. Muscle mass was not associated with incident diabetes, but every 5-kg increase in grip strength was associated with 13% lower incidence of type 2 diabetes. While this association likely reflects a relationship between overall muscle function – rather than grip strength per se – and risk of diabetes, grip strength is quick and easy to measure and could potentially be incorporated into routine clinical consultations.
Thus, while the available data are relatively limited, and further study is needed, there is now emerging evidence that sleep variables and grip strength may contribute to an individual’s risk of type 2 diabetes. Intervention studies are needed to determine whether altering sleep behaviours and improving strength could, alongside weight loss and increasing physical activity, potentially help reduce risk of developing type 2 diabetes in individuals at high risk.
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