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Poor sleep increases diabetes risk regardless of healthy eating habits, study finds
In a recent study published in JAMA Network Open, researchers explored how an individual’s sleep duration and dietary habits are associated with their likelihood of developing type 2 diabetes (T2D).
Their results, obtained from a cohort study, indicate that poor sleep and unhealthy dietary patterns are risk factors for T2D and have implications for public health strategies to prevent diabetes.
Background
Researchers consider people who sleep less than seven hours a day to have short sleep duration, and studies suggest that up to one-third of adults could be short sleepers.
Not receiving adequate sleep may increase the risk of multiple adverse health outcomes, including T2D, since sleep restriction may affect insulin resistance and glucose metabolism.
While increasing sleep duration to at least seven hours a day could reduce T2D risk, many factors limit an individual’s ability to get sufficient sleep, primarily economic pressures, work schedules, and childcare responsibilities.
However, healthy dietary habits could counteract the adverse effects of poor sleep on health, including T2D risk.
About the study
In this UK-based study, researchers hypothesized that following healthy dietary habits would be associated with a lower risk of developing T2D among individuals who are short-sleepers.
The cohort study included assessments of dietary habits, daily sleep duration, and incident T2D as the primary outcome of interest.
For the sleep assessment, participants between the ages of 38 and 71 were asked to report how many hours they slept in each 24 hours, including naps.
People who slept seven to eight hours had a ‘normal’ sleep duration, while six hours was considered ‘mild short’ sleep, five hours ‘moderate short’ sleep, and three to four hours ‘extreme short’ sleep.
The dietary habit questionnaire included questions on consuming unprocessed and processed red meat, vegetables, fruit, and fish.
Individuals who consumed fewer than two servings each of processed and unprocessed red meat items and two or more servings of fish in a week were categorized as healthier, as were those who consumed at least four tablespoons of vegetables and two fruit pieces per day.
Each of these five behaviors was equally weighted so that individuals received a score between zero, representing the unhealthiest, and five, the healthiest. Hospital inpatient records were used to ascertain whether an individual developed T2D.
Researchers analyzed the data using proportional hazards regression analysis accounting for a dose-response relationship between T2D risk and sleep duration.
Additive and multiplicative interactions between sleep duration and diet scores were also modeled.
Adjusted models also included sex, ethnicity and race, smoking status, alcohol consumption, body mass index, blood pressure, education, physical activity, and antidepressant use. All-cause mortality was included as a possible competing outcome.
Findings
The study included 247,867 individuals who were 60 years old on average. Slightly over half the sample was female, and nearly 94% reported White Europeans as their race or ethnicity.
Slightly over three-fourths of the sample were categorized as normal sleepers; about 20% had mild short sleep, 4% were moderately short sleepers, and less than 1% were extremely short sleepers.
Only 17% scored five points on the healthy diet score, while 29%, 27.5%, 17.6%, and 1.5% received scores of four, three, two, and one, respectively. About 3.2% of the sample (7905 people) received a T2D diagnosis within a median of 12.5 years.
Compared to the reference group of normal sleepers, people who slept five hours each night were 16% more likely to develop T2D, while those who slept three to four hours were 41% more likely. However, normal sleep was not significantly different from mild short sleep.
Compared to those with the least healthy diets, people who scored four or five on the diet score were 25% less likely to develop T2D. Three, two, and one score were not associated with significantly lower risk than the reference group.
Researchers observed no multiplicative or additive interactions between diet score and sleep duration in both unadjusted and adjusted models. Sensitivity analysis that included all-cause mortality did not change the main findings.
Conclusions
The primary finding from this study indicates that habitually short sleepers may be at increased risk of developing T2D even if they maintain a healthy diet.
Inadequate sleep may impair insulin sensitivity at the cellular level, shift skeletal muscle energy metabolism toward non-glucose oxidation, increase activity in the sympathetic nervous system, and modify microbiota communities in the gut.
Since increasing sleep duration may not be feasible for many people, other strategies must be identified to reduce T2D risk. Interventions that can be investigated include following Mediterranean or similarly healthy diets and increasing physical exercise.
Additionally, future research should address other causes of inadequate sleep unrelated to economic and caregiving needs, such as obstructive sleep apnea.
注释：
cohort: n
表示" 一群人"，means "a company of companions or supporters"，如：The gangster walked into the room surrounded by his cohort. 一名匪徒走进被他的一帮人包围的屋子。
cellular: adj
表示" 细胞的；多孔的"，means "relating to cells"，如：Despite recent rapid changes in cellular molecular biology, methods of cell culture have been slow to change. 虽然细胞分子生物学近年来发展很快,但是细胞培养的方法变化很慢。
skeletal: adj
表示"骨骼的；梗概的"，means "of or relating to or forming or attached to a skeleton"，如：These foods replenish the skeletal needs of the body. 这些食物补充身体骨骼的需要。
microbiota: n
表示"微生物区,微生物丛"，如：Eventually, an individual's gut microbiota becomes as unique as a fingerprint. 最终每个人体内的微生物种类变得像指纹一样独特。
Intervention: n
表示" 介入；干预；"，means " involvement;intrusion"，如：His untimely intervention annoyed me. 他那不合时宜的干涉让我生气。
apnea: n
表示"呼吸暂停；窒息"，means "transient cessation of respiration"，如：Sleep apnea also increases the short-term risk of surgery. 睡眠呼吸暂停也增加了手术的风险。
中文简要说明：
2020年一份统计报告显示，全球超过4.62亿人患第2型糖尿病，堪称跨国公卫问题。瑞典一项近25万人研究显示，睡眠不足可能会导致罹患第2型糖尿病（type 2 diabetes）机率升高。每晚睡眠少于6小时，罹病风险增16%；每晚睡眠仅3到4小时者，罹病风险高出41%。值得注意的是，即使平时维持良好的饮食习惯，仍不足以完全抵销长期睡眠不足带来的负面影响。
英国《每日邮报》、医疗保健新闻网站News Medical报导，瑞典乌普萨拉大学（Uppsala University）团队追踪24万7867名英国人作息与健康状况，包括饮食习惯、每天睡眠时数（包括小睡）等等。
每天睡眠7到8小时列为正常时数，6小时为「略少」，5小时为「颇少」，3到4小时为「极少」。饮食习惯调查包括是否摄取加工或未经加工的红肉、蔬菜、水果、鱼类等，每周吃加工或未加工红肉各少于2份、鱼肉2份以上，每天吃蔬菜4匙以上、水果2块以上，就归类于饮食较为健康的一群，这5类食材得分权重相同，每人得分介于0到5分。
受试者年龄介于38岁至71岁，均龄60岁，女性略多于男性，94%为白人。睡眠正常者占比略高于75%，20%睡眠略少，4%睡眠颇少，1%睡眠极少。17%饮食得5分，1.5%得1分。
12.5年之内，3.2%（7905人）确诊罹患第2型糖尿病。与睡眠正常者相较，每晚睡5小时者患病机率高16%，睡眠3到4小时者高出41%，睡6小时者没有显著差异。与饮食最不健康者相较，得分4到5分者罹病风险低了25%。
然而长期睡眠时数太少的人，即使保持健康饮食习惯，罹患第2型糖尿病风险仍会增加。睡眠不足会损害细胞的胰岛素敏感性，影响新陈代谢，引起第2行糖尿病，高血糖会导致心脏病、中风，眼睛、肾脏、足部都会发生问题。研究报告作者、乌普萨拉大学睡眠研究员班奈迪克（Christian Benedict）表示，他通常建议大众优先顾及睡眠，睡足7到9小时的人摄取的热量较少，对于长期新陈代谢良好有所帮助。
研究团队表示，睡眠不足与糖尿病罹病风险增加之间的关系仍待进一步研究，然而睡足7到9小时对很多人而言不容易做到，因此有待透过进一步研究订定降低罹病风险的策略，例如遵循特定饮食习惯、增加运动量。研究成果已于本月5日发表于《美国医学会期刊》网络开放版（JAMA Network Open）。
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