Association Between Nonrestorative Sleep and Risk of Diabetes: A Cross-Sectional Study

Nonrestorative Sleep and Type 2 Diabetes Incidence: The Aichi Workers' Cohort Study

BACKGROUND

The term "nonrestorative sleep (NRS)" refers to an unrefreshed feeling at wake-up and is a domain of poor sleep quality. Previous research has demonstrated that NRS is linked to a number of diseases and adverse health outcomes, but less is known regarding the link between NRS and diabetes, particularly in Japanese.

METHODS

We studied 3,665 middle-aged male participants of the Aichi Workers' Cohort Study who were followed-up from 2002 through 2019. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of incident type 2 diabetes mellitus (T2DM) in relation to NRS adjusted for potential confounding variables.

RESULTS

During a median follow-up of 14.6 years, 421 type 2 diabetes cases were identified. Participants with NRS had a higher crude incidence rate of T2DM (11.2/1,000 person-years), compared to participants without NRS (9.3/1,000 person-years). In the fully adjusted model, individuals who reported having NRS had a significantly higher risk of developing T2DM (HR1.36; 95% CI, 1.10-1.67). The association was observed only in participants under 50 years old (HR 1.82; 95% CI, 1.36-2.43), not in the older (50 years or older) participants (P for interaction = 0.025). In contrast, stratified analyses by the presence of shift work, obesity, or sleep duration showed similar associations in all the strata.

CONCLUSION

NRS was associated with higher risk of T2DM in middle-aged Japanese male workers independent of a variety of lifestyle factors and other sleep problems.

The effect of nonrestorative sleep on incident hypertension 1-2 years later among middle-aged Hispanics/Latinos

BACKGROUND

Insomnia is known to be a major risk factor for incident hypertension. Nonrestorative sleep (NRS), which refers to insufficiently rested sleep, has reported to associate with various diseases. This study aimed to investigate the longitudinal association between insomnia-related symptoms including NRS and incident hypertension 1-2 years later by age group (young, 18-39 years and middle-age, 40-64 years) using existing cohort data involving Hispanics/Latinos.

METHODS

This study included 1100 subjects who had participated in both the Hispanic Community Health Study/Study of Latinos and its follow-up study, the Sueño Ancillary Study, and met additional eligibility criteria. Incident hypertension was assessed by self-reported history and/or the use of antihypertensives. The Women's Health Initiative Insomnia Rating Scale (WHIIRS) was used to evaluate insomnia-related symptoms (difficulty initiating sleep, difficulty maintaining sleep, early morning awakening, difficulty returning to sleep, and NRS). Logistic regression analyses were conducted to assess the degree to which insomnia-related symptoms at baseline predicted incident hypertension.

RESULTS

Among the participants (64% middle-aged, 36% young adults), 140 (12.7%) developed hypertension during the follow-up period. Among the sleep-related symptoms, only NRS predicted incident hypertension after adjusting for sociodemographic factors and physical condition (odds ratio: 1.88, 95% confidence interval: 1.10-3.21, p = 0.022) in middle-aged adults. None of the insomnia-related symptoms were associated with incident hypertension in the young adults. No association was found between WHIIRS-defined insomnia (total score ≥ 9) and incident hypertension in middle-aged adults or young adults.

CONCLUSION

The present findings suggest the importance of focusing on NRS to help prevent the development of hypertension in middle-aged adults.

Development and validation of the Japanese version of the Restorative Sleep Questionnaire in community samples

OBJECTIVE

This study aimed to validate the Japanese version of the Restorative Sleep Questionnaire Weekly version (RSQ-W-J) and estimate the RSQ-W-J cut-off score to identify the degree of non-restorative sleep (NRS) that interferes with daytime function.

METHODS

An online survey was conducted, and 513 participants (241 men, 272 women; mean age, 47.88 ± 16.66 years) completed the questionnaires. The RSQ-W-J, Multidimensional Fatigue Inventory, Athens Insomnia Scale, Patient Health Questionnaire-9, Epworth Sleepiness Scale, Sleep Debt Index, NRS and the degree of daytime dysfunction, and the diagnostic criteria for chronic insomnia were used as implementation scales.

RESULTS

The RSQ-W-J was confirmed to have a single-factor structure. Both the Cronbach α coefficient and test-retest reliability of RSQ-W-J were high (α = 0.91; intraclass correlation coefficient [ICC]_agreement = 0.85). The RSQ-W-J was significantly negatively correlated with the scales of fatigue, insomnia, depressive symptoms, daytime sleepiness, and sleep debt. In addition, the RSQ-W-J scores of the insomnia group, in which participants met the diagnostic criteria for chronic insomnia, NRS group, in which participants had NRS only, and sleep debt group, in which participants had sleep debt, were significantly lower than those in the normal sleep group. Furthermore, the insomnia group scored significantly lower than the sleep debt group. The RSQ-W-J cut-off score, which indicates whether or not NRS interferes with daytime function, was estimated to be 45.8 points.

CONCLUSIONS

The RSQ-W-J was shown to be useful for comprehensively measuring the degree of restorative sleep.

Nonrestorative sleep is a risk factor for metabolic syndrome in the general Japanese population

BACKGROUND

This longitudinal study aimed to investigate the effects of nonrestorative sleep on developing metabolic syndrome (MetS) and related diseases in a general Japanese middle-aged population.

METHODS

Overall, 83,224 adults without MetS (mean age: 51.5 ± 3.5 years) from the Health Insurance Association in Japan were followed up for a maximum of 8 years between 2011 and 2019. The Cox proportional hazard method was used to determine whether nonrestorative sleep, assessed using a single-item question, was significantly associated with the respective development of MetS, obesity, hypertension, diabetes, and dyslipidemia. The MetS criteria were adopted by the Examination Committee for Criteria of Metabolic Syndrome in Japan.

RESULTS

The mean follow-up duration was 6.0 years. The incidence rate of MetS was 50.1 person-years/1,000 during the study period. Data suggested that nonrestorative sleep was associated with MetS (hazard ratio [HR]: 1.12, 95% confidence interval [CI]: 1.08-1.16) and other disorders, such as obesity (HR: 1.07, 95% CI: 1.02-1.12), hypertension (HR: 1.07, 95% CI: 1.04-1.11), and diabetes (HR: 1.07, 95% CI: 1.01-1.12) but not with dyslipidemia (HR: 1.00, 95% CI: 0.97-1.03).

CONCLUSIONS

Nonrestorative sleep is associated with the development of MetS and many of its core components in the middle-aged Japanese population. Therefore, assessing nonrestorative sleep may help identify individuals at a risk of MetS development.

Longitudinal assessment of lifestyle factors associated with nonrestorative sleep in Japan

OBJECTIVE

Nonrestorative sleep (NRS) is common in the general global population. This study surveyed the incident/remission rate of NRS and identified related lifestyle factors in a general Japanese adult cohort.

METHODS

Data from a Japanese health check-based cohort between the fiscal years 2011 and 2018 were obtained. NRS was assessed through a single item question, and socio-demographic and clinical data were assessed through self-reports. To identify potential correlates of NRS incidence/remission, Cox regression analysis (or survival analysis) was performed.

RESULTS

Among the 135 609 individuals surveyed at baseline, data from 93 548 were considered for analysis. NRS exhibited incidence and remission rates of 11.3% and 15.4%, respectively. New NRS incidence was predicted by eating fast (hazard ratio [HR]: 1.07, 95% confidence interval [CI]: 1.04-1.10), dining close to bedtime (HR: 1.33, 95% CI: 1.27-1.38), midnight snacking (HR: 1.09, 95% CI: 1.04-1.13), skipping breakfast (HR: 1.16, 95% CI: 1.10-1.22), non-regular exercise (HR: 1.12, 95% CI: 1.07-1.17), lower levels of physical activity (HR: 1.19, 95% CI: 1.14-1.24), and slow walking speed (HR: 1.34, 95% CI: 1.29-1.39), while heavy drinking was less predictive of NRS. However, the same factors (except for heavy drinking) were found to predict NRS remission.

CONCLUSIONS

We found that unhealthy lifestyle behaviors, particularly dining close to bedtime and slow walking speed, were positively associated with NRS incidence, while they were negatively associated with NRS remission. These results can be useful in developing more effective health promotion policies to achieve good sleep.

Associations among Alcohol Drinking, Smoking, and Nonrestorative Sleep: A Population-Based Study in Japan

Nonrestorative sleep (NRS) is a common sleep disorder. It is associated with several unhealthy lifestyle factors, such as skipping breakfast and lack of exercise. However, the associations between alcohol drinking, smoking, and NRS are unclear. This study examined the prevalence of NRS within the Japanese general population and the relationships among alcohol drinking, smoking, and NRS. We analyzed an anonymized dataset from a 2013 nationwide population survey (35,717 men and 39,911 women). NRS was assessed through a single-item question, and socio-demographic and lifestyle factors were assessed through self-reports. Multivariable logistic regression analyses were used to examine the associations between alcohol drinking, smoking, and NRS. The total prevalence of NRS was 22.2% (95% CI 21.8-22.7) in men and 23.4% (95% CI 23.0-23.8) in women. Further, we found that sleep duration and prevalence of NRS shared an inverse J-shaped relationship. Heavy alcohol drinking was significantly associated with NRS in both sexes. Short sleep duration and certain socioeconomic factors modified the effect of smoking on NRS in men. These results could be useful in the development of more effective sleep health policies to establish better sleep hygiene.

Poor Eating Behaviors Related to the Progression of Prediabetes in a Japanese Population: An Open Cohort Study

This study aimed to examine lifestyle factors associated with the change in glucose categories among individuals without diabetes. We analyzed cohort data of medical check-ups at baseline between April 2008 and December 2012. The primary and secondary outcomes were the change in glucose categories from normoglycemia (glycated hemoglobin (HbA1c) < 5.7% and fasting plasma glucose (FPG) < 5.6 mmol/L) to prediabetes (HbA1c 5.7-6.4% or FPG 5.6-6.9 mmol/L) and from prediabetes to normoglycemia. During a mean follow-up of 2.4 years, 7083 of 57,018 individuals with normoglycemia developed prediabetes, whereas 4629 of 9926 individuals with prediabetes returned to normoglycemia. Factors associated with progression to prediabetes were baseline BMI (hazard ratio [95% confidence interval]: 1.08 [1.07-1.09]), change in BMI during follow-up (1.05 [1.03-1.07]), late dinner/snacking (1.16 [1.10-1.22]), skipping breakfast (1.12 [1.06-1.18]), and heavy alcohol consumption (1.33 [1.24-1.42]). Factors associated with return to normoglycemia from prediabetes were baseline BMI (0.94 [0.93-0.95]) and change in BMI during follow-up (0.95 [0.93-0.97]). In conclusion, poor eating behaviors, such as skipping breakfast, late dinner/snacking, and heavy alcohol consumption, were associated with the progression from normoglycemia to prediabetes.

Associations of nonrestorative sleep and insomnia symptoms with incident depressive symptoms over 1-2 years: Longitudinal results from the Hispanic Community Health Study/Study of Latinos and Sueño Ancillary Study

BACKGROUND

Nonrestorative sleep (NRS), defined as insufficiently rested or refreshed sleep, is considered to play an important role in the development of depression. The aim of this study is to investigate the predictive ability of insomnia-related symptoms, including NRS, for incident depressive symptoms (DEPs) in a longitudinal manner.

METHODS

We used data of 1196 samples aged 18-64 years who participated in both the Hispanic Community Health Study/Study of Latinos conducted in 2008-2010 and the follow-up study (Sueño Ancillary Study) conducted in 2010-2013. DEPs and insomnia-related symptoms (difficulty initiating sleep [DIS], difficulty maintaining sleep [DMS], early morning awakening [EMA], difficulty returning to sleep [DRS], and NRS) were evaluated by the 10-item Center for Epidemiologic Studies Depression Scale and the Women's Health Initiative Insomnia Rating Scale, respectively. A logistic regression analysis was used to evaluate the predictive ability of each insomnia-related symptom at baseline for incident DEPs in couple-years.

RESULTS

In the univariate logistic regression analysis, all insomnia-related symptoms had significant associations with incident DEPs (DIS, odds ratio [OR] = 1.6; DMS, OR = 1.6; EMA, OR = 1.5; DRS, OR = 1.9; NRS, OR = 2.5). After adjusting for sociodemographic factors and the confounding effects of other insomnia-related symptoms, only NRS (OR = 2.2, 95% confidence interval = 1.4-3.5, p = .001) was significantly associated with incident DEPs.

CONCLUSIONS

NRS was a risk factor for incident DEPs, which includes a predictive ability for other insomnia-related symptoms. Our results suggest that focusing on NRS is an effective strategy for preventing depression in public health promotions.

Sleep Quality among Patients with Type 2 Diabetes: A Cross-Sectional Study in the East Coast Region of Peninsular Malaysia

Poor sleep is related to type 2 diabetes and adversely influences a person’s quality of life. This study aimed to evaluate sleep quality in patients with type 2 diabetes (T2DM), its associated factors, and its relationship with quality of life. A cross-sectional study was conducted at a primary care clinic in a tertiary hospital on the east coast of Malaysia. This study included 350 participants (175 men and 175 women). Data were collected using the Malay version of the Pittsburgh Sleep Quality Index (PSQI-M) with a cut-off point of >5 as poor sleep, the Malay version of Diabetes Distress Scale (MDDS-17) and the revised Malay version of T2DM-related quality of life (Rv-DQOL). Statistical analysis was conducted using the SPSS software version 26.0. The respondents’ median (interquartile range (IQR)) age was 62.0 (11.0) years, and poor sleep was reported in 32% (95% confidence interval (CI) = 27.1, 36.9) of the participants. Multivariate logistic regression analysis revealed that poor sleep quality was significantly associated with nocturia (odds ratio (OR) = 2.04; 95% CI = 1.24, 3.35), restless legs syndrome (OR = 2.17; 95% CI = 1.32−3.56) and emotional burden (OR = 2.37; 95% CI = 1.41−3.98). However, no statistically significant association was observed between sleep quality and quality of life among our participants.

The association between nonrestorative sleep and health-related quality of life in Chinese adults: a cross-sectional study

PURPOSE

Sleep problems are prevalent among the general population and can cause various health problems, which may lead to decreased quality of life. However, little is known about nonrestorative sleep and its implications. This study aimed to examine the association between nonrestorative sleep and health-related quality of life (HRQL) in Chinese adults.

METHODS

Data were collected through a cross-sectional study of 500 adults in Hong Kong (66.4% female, average age of 39 years). The Short-Form-12 Health Survey version 2 (SF-12v2), Nonrestorative Sleep Scale (NRSS), Pittsburgh Sleep Quality Index, ENRICHD Social Support Instrument, Patient Health Questionnaire, Perceived Stress Scale, and Hospital Anxiety and Depression Scale were administered. Objective sleep parameters were based on participants' sleep condition over 1 week, as measured using an ActiGraph GT9X Link.

RESULTS

Mean standardized scores for the physical component summary (PCS) and mental component summary (MCS) of the SF-12v2 and the NRSS were 50.33 ± 6.50, 49.00 ± 9.03, and 64.77 ± 12.75, respectively. After adjusting for sociodemographic and lifestyle characteristics, sleep quality, objective sleep parameters, social support, somatic symptoms, stress, anxiety, and depression, NRSS scores were associated with PCS (b = 0.12, 95%CI: 0.06 to 0.18, p < 0.001) and MCS (b = 0.08, 95%CI: 0.02 to 0.15, p = 0.013) scores. Furthermore, associations of NRSS score with PCS as well as MCS scores were stronger in women than in men.

CONCLUSION

Nonrestorative sleep is a potentially modifiable risk factor for poor HRQL. Thus, interventions to relieve or decrease nonrestorative sleep could be beneficial for improving HRQL.

Nonrestorative sleep scale: a reliable and valid short form of the traditional Chinese version

Purpose

Previous research has suggested the essential unidimensionality of the 12-item traditional Chinese version of the Nonrestorative Sleep Scale (NRSS). This study aimed to develop a short form of the traditional Chinese version of the NRSS without compromising its reliability and validity.

Methods

Data were collected from 2 cross-sectional studies with identical target groups of adults residing in Hong Kong. An iterative Wald test was used to assess differential item functioning by gender. Based on the generalized partial credit model, we first obtained a shortened version such that further shortening would result in substantial sacrifice of test information and standard error of measurement. Another shortened version was obtained by the optimal test assembly (OTA). The two shortened versions were compared for test information, Cronbach’s alpha, and convergent validity.

Results

Data from a total of 404 Chinese adults (60.0% female) who had completed the Chinese NRSS were gathered. All items were invariant by gender. A 6-item version was obtained beyond which the test performance substantially deteriorated, and a 9-item version was obtained by OTA. The 9-item version performed better than the 6-item version in test information and convergent validity. It had discrimination and difficulty indices ranging from 0.44 to 2.23 and − 7.58 to 2.13, respectively, and retained 92% of the test information of the original 12-item version.

Conclusion

The 9-item Chinese NRSS is a reliable and valid tool to measure nonrestorative sleep for epidemiological studies.

Electronic supplementary material

The online version of this article (10.1007/s11136-020-02523-4) contains supplementary material, which is available to authorized users.

Nonrestorative sleep scale: reliable and valid for the Chinese population

PURPOSE

To conduct a linguistic and psychometric evaluation of a Chinese version of the Nonrestorative Sleep Scale (NRSS).

METHODS

The Chinese NRSS was created from a standard forward-backward translation and trialed on 10 Chinese adults. Telephone interviews were then conducted with 100 adults, who completed the Chinese NRSS, the Pittsburgh Sleep Quality Index (PSQI), the Athens Insomnia Scale (AIS), the Center for Epidemiological Studies Depression Scale (CES-D), and the Toronto Hospital Alertness Test (THAT). A household survey was conducted with 20 subjects, followed by a confirmatory factor analysis (CFA), and a bifactor model was developed to evaluate the reliability and validity of the NRSS.

RESULTS

The bifactor model had the root mean square error of approximation (RMSEA), standardized root mean square residual (SRMR), and comparative fit index (CFI) of 0.06, 0.06, and 0.97, respectively. Convergent validity was shown from the moderate associations with PSQI (r = - 0.66, P < 0.01), AIS (r = - 0.65, P < 0.01), CES-D (r = - 0.54, P < 0.01), and THAT (r = 0.68, P < 0.01). The coefficient omega (0.92), omega hierarchical (0.81), factor determinacy (0.93), H value (0.91), explained common variance (0.63), and percentage of uncontaminated correlations (0.80) derived from the bifactor CFA supported the essential unidimensionality of NRSS.

CONCLUSIONS

The Chinese NRSS is a valid and reliable essential unidimensional tool for the assessment of nonrestorative sleep in the Chinese population.