Displaying publications 41 - 60 of 188 in total

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  1. Fulltext Potential of Honeycomb-Filled Composite Structure in Composite Cross-Arm Component: A Review on Recent Progress and Its Mechanical Properties
    Amir AL, Ishak MR, Yidris N, Zuhri MYM, Asyraf MRM
    Polymers (Basel), 2021 Apr 20;13(8).
    PMID: 33923921 DOI: 10.3390/polym13081341
    Nowadays, pultruded glass fiber-reinforced polymer composite (PGFRPC) structures have been used widely for cross-arms in high transmission towers. These composite structures have replaced cross-arms of conventional materials like wood due to several factors, such as better strength, superior resistance to environmental degradation, reduced weight, and comparatively cheaper maintenance. However, lately, several performance failures have been found on existing cross-arm members, caused by moisture, temperature changes in the atmosphere, and other environmental factors, which may lead to a complete failure or reduced service life. As a potential solution for this problem, enhancing PGFRPC with honeycomb-filled composite structures will become a possible alternative that can sustain a longer service life compared to that of existing cross-arms. This is due to the new composite structures' superior performance under mechanical duress in providing better stiffness, excellence in flexural characteristics, good energy absorption, and increased load-carrying capacity. Although there has been a lack of previous research done on the enhancement of existing composite cross-arms in applications for high transmission towers, several studies on the enhancement of hollow beams and tubes have been done. This paper provides a state-of-the-art review study on the mechanical efficiency of both PGFRPC structures and honeycomb-filled composite sandwich structures in experimental and analytical terms.
    Matched MeSH terms: Maintenance
  2. Fulltext A Heuristic Approach for Optical Transceiver Placement to Optimize SNR and Illuminance Uniformities of an Optical Body Area Network
    Masroor K, Jeoti V, Drieberg M, Cheab S, Rajbhandari S
    Sensors (Basel), 2021 Apr 22;21(9).
    PMID: 33922288 DOI: 10.3390/s21092943
    The bi-directional information transfer in optical body area networks (OBANs) is crucial at all the three tiers of communication, i.e., intra-, inter-, and beyond-BAN communication, which correspond to tier-I, tier-II, and tier-III, respectively. However, the provision of uninterrupted uplink (UL) and downlink (DL) connections at tier II (inter-BAN) are extremely critical, since these links serve as a bridge between tier-I (intra-BAN) and tier-III (beyond-BAN) communication. Any negligence at this level could be life-threatening; therefore, enabling quality-of-service (QoS) remains a fundamental design issue at tier-II. Consequently, to provide QoS, a key parameter is to ensure link reliability and communication quality by maintaining a nearly uniform signal-to-noise ratio (SNR) within the coverage area. Several studies have reported the effects of transceiver related parameters on OBAN link performance, nevertheless the implications of changing transmitter locations on the SNR uniformity and communication quality have not been addressed. In this work, we undertake a DL scenario and analyze how the placement of light-emitting diode (LED) lamps can improve the SNR uniformity, regardless of the receiver position. Subsequently, we show that using the principle of reciprocity (POR) and with transmitter-receiver positions switched, the analysis is also applicable to UL, provided that the optical channel remains linear. Moreover, we propose a generalized optimal placement scheme along with a heuristic design formula to achieve uniform SNR and illuminance for DL using a fixed number of transmitters and compare it with an existing technique. The study reveals that the proposed placement technique reduces the fluctuations in SNR by 54% and improves the illuminance uniformity up to 102% as compared to the traditional approach. Finally, we show that, for very low luminous intensity, the SNR values remain sufficient to maintain a minimum bit error rate (BER) of 10-9 with on-off keying non-return-to-zero (OOK-NRZ) modulation format.
    Matched MeSH terms: Maintenance
  3. Fulltext Folie a deux complicate management of a childhood onset schizophrenia
    Seen, Heng Yeoh, Kok, Wei Wee, Maryam Amaran, Hazura Hamzah
    ASEAN Journal of Psychiatry, 2012;13(2):0-0.
    MyJurnal
    Objective: This case report highlights folie a duex of a caregiver that complicate the management of a case of childhood onset schizophrenia.
    Methods: We report a case of a young Malay girl with symptoms of schizophrenia and her caregiver who share her delusion.
    Result: Folie a duex in the caregiver caused difficulty in the initiation and maintenance of treatment of a child with schizophrenia.
    Conclusion: Treating children with schizophrenia is not easy and could be complicated by the folie a duex in caregiver. Although Child Act 2001 can be applied in order to deliver appropriate treatment to this group of patients, one must be cautious about the implication in therapeutic alliance.
    Matched MeSH terms: Maintenance
  4. Fulltext Factors affecting the cold flow behaviour of biodiesel and methods for improvement - a review
    Edith, Odeigah, Janius, Rimfiel B., Robiah Yunus
    Pertanika Journal of Science & Technology, 2012;20(1):1-14.
    MyJurnal
    Biodiesel is an attractive renewable energy source, which is suitable as a substitute to the non-renewablepetroleum diesel. However, it is plagued by its relatively bad cold flow behaviour. In this review, the factorsaffecting the cold flow of biodiesel, vis-à-vis the contradicting requirement of good cold flow and good ignitionproperties, are discussed. Fuel filter plugging, and crystallization of biodiesel are considered, together with thecold flow properties such as Pour Point (PP), Cloud Point (CP), Cold Filter Plugging Point (CFPP) and LowTemperature Filterability Test (LTFT). In addition, various methods used to improve the cold flow of biodieselare also presented, with a special emphasis laid on the effects of these methods in reducing the Cloud Point.Strategies to improve cold flow, and yet maintaining the good ignition quality of biodiesel, are also proposed.As far as the cold flow of biodiesel is concerned, desirable attributes of its esters are short, unsaturated andbranched carbon chains. However, these desirable attributes present opposing properties in terms of ignitionquality and oxidation stability. This is because esters with short, unsaturated and branched carbon chainspossess very good cold flow but poor ignition quality and oxidation stability. The target is therefore to producebiodiesel with good cold flow, sufficient ignition quality, and good oxidation stability. This target proves tobe quite difficult and is a major problem in biodiesel research. New frontiers in this research might be thedesign of the new cold flow improvers that is similar to those used in the petroleum diesel but is tailored forbiodiesel. Genetic modifications of the existing feedstock are also desirable but the food uses of this particularfeedstock should always be taken into consideration.
    Matched MeSH terms: Maintenance
  5. Fulltext The effects of airflow on oven temperatures and cakes qualities
    Shahapuzi, N.S., Taip, F. S., Aziz, N., Ahmedov, A.
    Pertanika Journal of Science & Technology, 2015;23(2):339-350.
    MyJurnal
    The presence of airflow during heating process is expected to increase heat uniformity in a closed heating chamber. Circulation of hot air increases the percentage of convective heat transfer. In this study effects of airflow on oven temperature, cake temperature and several cake qualities were investigated. Experimental studies were conducted in convective oven using two different baking modes; with and without airflow. During baking, oven temperatures and internal cake temperature were measured, and images of cake expansion were captured. Results of the study showed that the presence of airflow could maintain the oven temperature within a small range of set point temperature. Temperature in the oven exhibited ±5.5°C fluctuation, approximately 3.5% overshoot that occurred continuously during baking with airflow. On the contrary, higher overshoot (ranging from 15 to 30%) was observed in oven temperature without airflow. Airflow also showed a significant effect (p
    Matched MeSH terms: Maintenance
  6. Fulltext Microstructure analysis, physical and thermal properties of al2o3-al2tio5 functionally graded ceramics for the application of car brake rot
    Oo, Z., Sujan, D., Rong Kimberly, F. P
    Pertanika Journal of Science & Technology, 2015;23(1):153-161.
    MyJurnal
    Aluminium titanate (AT) (Al2TiO5) is a promising engineering material because of its low thermal expansion coefficient, excellent thermal shock resistance, good refractoriness and non-wetting with most metals. Functionally graded material (FGM) is generally a particulate composite with continuously varying volume fractions. FGMs are alternative materials for dental implants, building materials and ballistic protection. It has been of great interest to future engines, internal combustion engines, metal cutting and other high temperature engineering application. There has been a demand for an adequate disc brake that requires less maintenance in the automotive manufacturing industry. FGM, the next evolution of layered structure, consists of graded compositions that are dispersed across the ceramic which produces a gradual improvement in the properties across the ceramic at a steady pace.
    Matched MeSH terms: Maintenance
  7. Fulltext Trend analysis of water quality at Sungai Sarawak
    Yuhani Jamian, Zainap Lamat, Nurazura Rali
    Pertanika Journal of Science & Technology, 2017;25(105):55-62.
    MyJurnal
    Sungai Sarawak is the most important river in Sarawak. This study was aimed at assessing water quality in the selected stations from Satok bridge to the downstream, Muara Tebas, located along Sungai Sarawak. Water quality trend analysis was conducted to determine the correlation between the water quality parameters. Trend analysis was carried out using Mann-Kendall Test because data collected was non-parametric. Next, Spearman rank was used in order to determine the correlation between parameters. The results obtained and the observation made in this study reveals that the trend exists only for Chemical Oxygen Value (COD). But there are trends for Biochemical Oxygen Demand, (BOD), Dissolved Oxygen (DO), Total Suspended Solid (TSS), Ammoniacal Nitrogen (NH4N) and Turbidity to decrease or increase with no trends between 2007 and 2011. The correlation between parameters is not very strong because there are many determinants of water quality parameters. The result from this study would provide useful information for water quality management in order to maintain and improve the water quality of Sungai Sarawak.
    Matched MeSH terms: Maintenance
  8. Fulltext Fuzzy-controlled humidity variation by Silica gel and Nitrogen gas in an atmospheric chamber
    Ali Ghahraei, Nurul Amziah Md Yunus, Izhal Abdul Halin, Nasri Sulaiman
    Pertanika Journal of Science & Technology, 2017;25(102):133-142.
    MyJurnal
    Controlled humidity environment is of significance in many scientific researches and experiments. In most laboratory-scale atmospheric chambers, an electrical temperature-based control system is used to adjust humidity. Since these chambers are not affordable in every laboratory, other low cost chambers using nitrogen gas or silica gel are used to adjust humidity. In this paper, a mechanism was developed to control the relative humidity in closed lab-scale chambers. Humidification is done by spraying water through a blower fan while de-humidification is by pumping air through silica gel as well as nitrogen gas injection. A Mamdani type fuzzy controller was designed to control the components and relative humidity. The results show the proposed system and controller can adjust and maintain relative humidity from 41% to 100% with maximum overshoot of 1% and the maximum range of error of steady state of 1.2 %.
    Matched MeSH terms: Maintenance
  9. Fulltext Homeownership affordability: an analysis of household socio‐economic
    Norizan Rameli, Dani Salleh, Mazlan Ismail
    Malaysian Journal of Social Sciences and Humanities, 2016;1(1):10-16.
    MyJurnal
    Homeownership affordability is not only the ability of households to pay the housing cost. But homeownership affordability is also involving the ability of households to pay housing costs as well as to maintain the basic needs in the continuity of life. Thus, affordability aspect is important in home ownership. Meanwhile, home ownership is the biggest decision for a household in a term. The combination of affordability and homeownership led to research on factors that affect the affordability of homeownership, especially in terms of socio-economic households inclusively. Socio-economic factors as discussed include income, household expenditures, job type, education level, number of dependents, monthly housing loan and financial savings. Each factor plays the role of its own to ensure the affordability level of homeownership. In fact, the factors that affect the homeownership affordability is different between households. Analysis of the socio-economic factors is necessary because homeownership affordability issues impact the quality life of mankind.
    Matched MeSH terms: Maintenance
  10. Fulltext Development of community-based early warning system (CBEWS) in enhancing community preparedness for dam-related disasters in Malaysia
    Azrul Ghazali, Sivadass Thiruchelvam, Kamal Nasharuddin Mustapha, Ahmad Kamal Kadir, Fatin Faiqa Norkhairi, Nora Yahya, et al.
    ASM Science Journal, 2018;11(2):117-123.
    MyJurnal
    Series of catastrophic floods that we have witnessed over the last decade in Malaysia have necessitated the adoption of reliable early warning system. Ultimate concern during any event of natural or manmade disaster would be information dissemination to lessen the disaster impact on lives and property. The Bertam Valley incident in the wee hours of 23rd October 2013 has been considered as the game changer of how we view the role of vulnerable communities in facing dam-related disasters. Empowerment of local communities has been considered as vital in disaster management, as they are often the first responders to disaster. Local Community-Based Early Warning System (CBEWS) is a smart mechanism operated by the communities. This study revolves around the actual implementation of such system in Cameron Highlands in the effort of increasing human resilience towards damrelated disasters. While establishing the system, the Bertam Valley community has received support from different individuals and organisations. It is paramount that the community develops and maintains close coordination and strong links with these stakeholders. The performance of early warning systems can be evaluated via key parameters such as timeliness, accuracy, reliability, user friendliness, flexibility, and costs & benefits.
    Matched MeSH terms: Maintenance
  11. Fulltext SmartFire: Intelligent Platform for Monitoring Fire Extinguishers and Their Building Environment
    Garcia-Martin R, González-Briones A, Corchado JM
    Sensors (Basel), 2019 May 25;19(10).
    PMID: 31130598 DOI: 10.3390/s19102390
    Due to fire protection regulations, a minimum number of fire extinguishers must be available depending on the surface area of each building, industrial establishment or workplace. There is also a set of rules that establish where the fire extinguisher should be placed: always close to the points that are most likely to be affected by a fire and where they are visible and accessible for use. Fire extinguishers are pressure devices, which means that they require maintenance operations that ensure they will function properly in the case of a fire. The purpose of manual and periodic fire extinguisher checks is to verify that their labeling, installation and condition comply with the standards. Security seals, inscriptions, hose and other seals are thoroughly checked. The state of charge (weight and pressure) of the extinguisher, the bottle of propellant gas (if available), and the state of all mechanical parts (nozzle, valves, hose, etc.) are also checked. To ensure greater safety and reduce the economic costs associated with maintaining fire extinguishers, it is necessary to develop a system that allows monitoring of their status. One of the advantages of monitoring fire extinguishers is that it will be possible to understand what external factors affect them (for example, temperature or humidity) and how they do so. For this reason, this article presents a system of soft agents that monitors the state of the extinguishers, collects a history of the state of the extinguisher and environmental factors and sends notifications if any parameter is not within the range of normal values.The results rendered by the SmartFire prototype indicate that its accuracy in calculating pressure changes is equivalent to that of a specific data acquisition system (DAS). The comparative study of the two curves (SmartFire and DAS) shows that the average error between the two curves is negligible: 8% in low pressure measurements (up to 3 bar) and 0.3% in high pressure (above 3 bar).
    Matched MeSH terms: Maintenance
  12. Fulltext Embedded Smart Antenna for Non-Destructive Testing and Evaluation (NDT&E) of Moisture Content and Deterioration in Concrete
    Teng KH, Kot P, Muradov M, Shaw A, Hashim K, Gkantou M, et al.
    Sensors (Basel), 2019 Jan 28;19(3).
    PMID: 30696110 DOI: 10.3390/s19030547
    : Concrete failure will lead to serious safety concerns in the performance of a building structure. It is one of the biggest challenges for engineers to inspect and maintain the quality of concrete throughout the service years in order to prevent structural deterioration. To date, a lot of research is ongoing to develop different instruments to inspect concrete quality. Detection of moisture ingress is important in the structural monitoring of concrete. This paper presents a novel sensing technique using a smart antenna for the non-destructive evaluation of moisture content and deterioration inspection in concrete blocks. Two different standard concrete samples (United Kingdom and Malaysia) were investigated in this research. An electromagnetic (EM) sensor was designed and embedded inside the concrete to detect the moisture content within the structure. In addition, CST microwave studio was used to validate the theoretical model of the EM sensor against the test data. The results demonstrated that the EM sensor at 2.45 GHz is capable of detecting the moisture content in the concrete with linear regression of R² = 0.9752. Furthermore, identification of different mix ratios of concrete were successfully demonstrated in this paper. In conclusion, the EM sensor is capable of detecting moisture content non-destructively and could be a potential technique for maintenance and quality control of the building performance.
    Matched MeSH terms: Maintenance
  13. Fulltext Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components
    Rahman MNA, Zubir NSM, Leuveano RAC, Ghani JA, Mahmood WMFW
    Materials (Basel), 2014 Dec 02;7(12):7706-7721.
    PMID: 28788270 DOI: 10.3390/ma7127706
    The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers' high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s).
    Matched MeSH terms: Maintenance
  14. Fulltext GreenVMAS: Virtual Organization Based Platform for Heating Greenhouses Using Waste Energy from Power Plants
    González-Briones A, Chamoso P, Yoe H, Corchado JM
    Sensors (Basel), 2018 Mar 14;18(3).
    PMID: 29538351 DOI: 10.3390/s18030861
    The gradual depletion of energy resources makes it necessary to optimize their use and to reuse them. Although great advances have already been made in optimizing energy generation processes, many of these processes generate energy that inevitably gets wasted. A clear example of this are nuclear, thermal and carbon power plants, which lose a large amount of energy that could otherwise be used for different purposes, such as heating greenhouses. The role of GreenVMAS is to maintain the required temperature level in greenhouses by using the waste energy generated by power plants. It incorporates a case-based reasoning system, virtual organizations and algorithms for data analysis and for efficient interaction with sensors and actuators. The system is context aware and scalable as it incorporates an artificial neural network, this means that it can operate correctly even if the number and characteristics of the greenhouses participating in the case study change. The architecture was evaluated empirically and the results show that the user's energy bill is greatly reduced with the implemented system.
    Matched MeSH terms: Maintenance
  15. Fulltext Passive Fit in Screw Retained Multi-unit Implant Prosthesis Understanding and Achieving: A Review of the Literature
    Buzayan MM, Yunus NB
    J Indian Prosthodont Soc, 2014 Mar;14(1):16-23.
    PMID: 24604993 DOI: 10.1007/s13191-013-0343-x
    One of the considerable challenges for screw-retained multi-unit implant prosthesis is achieving a passive fit of the prosthesis' superstructure to the implants. This passive fit is supposed to be one of the most vital requirements for the maintenance of the osseointegration. On the other hand, the misfit of the implant supported superstructure may lead to unfavourable complications, which can be mechanical or biological in nature. The manifestations of these complications may range from fracture of various components in the implant system, pain, marginal bone loss, and even loss of osseointegration. Thus, minimizing the misfit and optimizing the passive fit should be a prerequisite for implant survival and success. The purpose of this article is to present and summarize some aspects of the passive fit achieving and improving methods. The literature review was performed through Science Direct, Pubmed, and Google database. They were searched in English using the following combinations of keywords: passive fit, implant misfit and framework misfit. Articles were selected on the basis of whether they had sufficient information related to framework misfit's related factors, passive fit and its achievement techniques, marginal bone changes relation with the misfit, implant impression techniques and splinting concept. The related references were selected in order to emphasize the importance of the passive fit achievement and the misfit minimizing. Despite the fact that the literature presents considerable information regarding the framework's misfit, there was not consistency in literature on a specified number or even a range to be the acceptable level of misfit. On the other hand, a review of the literature revealed that the complete passive fit still remains a tricky goal to be achieved by the prosthodontist.
    Matched MeSH terms: Maintenance
  16. Fulltext Osseointegration: an update
    Parithimarkalaignan S, Padmanabhan TV
    J Indian Prosthodont Soc, 2013 Mar;13(1):2-6.
    PMID: 24431699 DOI: 10.1007/s13191-013-0252-z
    Osseointegration, defined as a direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant, is critical for implant stability, and is considered a prerequisite for implant loading and long-term clinical success of end osseous dental implants. The implant-tissue interface is an extremely dynamic region of interaction. This complex interaction involves not only biomaterial and biocompatibility issues but also alteration of mechanical environment. The processes of osseointegration involve an initial interlocking between alveolar bone and the implant body, and later, biological fixation through continuous bone apposition and remodeling toward the implant. The process itself is quite complex and there are many factors that influence the formation and maintenance of bone at the implant surface. The aim of this present review is to analysis the current understanding of clinical assessments and factors that determine the success & failure of osseointegrated dental implants.
    Matched MeSH terms: Maintenance
  17. Using mental imagery to deliver self-regulation techniques to improve sleep behaviors
    Loft MH, Cameron LD
    Ann Behav Med, 2013 Dec;46(3):260-72.
    PMID: 23640130 DOI: 10.1007/s12160-013-9503-9
    BACKGROUND: Poor sleep habits and insufficient sleep represent significant workplace health issues.

    PURPOSE: Applying self-regulation theory, we conducted a randomized, controlled trial testing the efficacy of mental imagery techniques promoting arousal reduction and implementation intentions to improve sleep behavior.

    METHOD: We randomly assigned 104 business employees to four imagery-based interventions: arousal reduction, implementation intentions, combined arousal reduction and implementation intentions, or control imagery. Participants practiced their techniques daily for 21 days. They completed online measures of sleep quality, behaviors, and self-efficacy at baseline and Day 21; and daily measures of sleep behaviors.

    RESULTS: Participants using implementation intention imagery exhibited greater improvements in self-efficacy, sleep behaviors, sleep quality, and time to sleep relative to participants using arousal reduction and control imagery.

    CONCLUSIONS: Implementation intention imagery can improve sleep behavior for daytime employees. Use of arousal reduction imagery was unsupported. Self-regulation imagery techniques show promise for improving sleep behaviors.

    Matched MeSH terms: Sleep Initiation and Maintenance Disorders/psychology; Sleep Initiation and Maintenance Disorders/therapy*
  18. Managed care storms Malaysia. Fears are brewing that consumers will be hurt in the transition to privatized U.S.-style HMOs
    Rauber C
    Mod Healthc, 1999 Nov 15;29(46):50, 52, 55.
    PMID: 10662048
    Matched MeSH terms: Health Maintenance Organizations/trends*; Health Maintenance Organizations/utilization
  19. The relationship between Type D personality and insomnia
    Akram U, McCarty K, Akram A, Gardani M, Tan A, Villarreal D, et al.
    Sleep Health, 2018 08;4(4):360-363.
    PMID: 30031529 DOI: 10.1016/j.sleh.2018.04.005
    OBJECTIVES: Type D personality is characterized by the combination of social inhibition and negative affectivity. This study examined the relationship between Type D personality and insomnia symptoms amongst a sample of the general-population.

    METHODS: Adults from the general-population (n = 392) completed online measures of Type D personality (DS14) and insomnia severity.

    RESULTS: Individuals with the Type D personality trait reported significantly greater symptoms of insomnia relative to Non-Type Ds. Moreover, insomnia-symptoms were independently related to negative affectivity (NA) and social inhibition (SI) and the Type D interaction (i.e. synergistic product of SI and NA). Linear regression analysis determined that NA but not SI significantly predicted insomnia symptoms after controlling for age and sex. However, after accounting for the Type D interaction, negative affectivity remained the only significant predictor of insomnia-symptoms.

    CONCLUSIONS: The Type D personality type appears to be related to insomnia-symptoms, both as a categorical and dimensional construct. These outcomes support prior research evidencing that whilst Type D personality is related to poor sleep in adolescents, NA appears to be the main contributor.

    Matched MeSH terms: Sleep Initiation and Maintenance Disorders/epidemiology; Sleep Initiation and Maintenance Disorders/psychology*
  20. Fulltext Timing and Length of Nocturnal Sleep and Daytime Napping and Associations With Obesity Types in High-, Middle-, and Low-Income Countries
    Tse LA, Wang C, Rangarajan S, Liu Z, Teo K, Yusufali A, et al.
    JAMA Netw Open, 2021 06 01;4(6):e2113775.
    PMID: 34190997 DOI: 10.1001/jamanetworkopen.2021.13775
    Importance: Obesity is a growing public health threat leading to serious health consequences. Late bedtime and sleep loss are common in modern society, but their associations with specific obesity types are not well characterized.

    Objective: To assess whether sleep timing and napping behavior are associated with increased obesity, independent of nocturnal sleep length.

    Design, Setting, and Participants: This large, multinational, population-based cross-sectional study used data of participants from 60 study centers in 26 countries with varying income levels as part of the Prospective Urban Rural Epidemiology study. Participants were aged 35 to 70 years and were mainly recruited during 2005 and 2009. Data analysis occurred from October 2020 through March 2021.

    Exposures: Sleep timing (ie, bedtime and wake-up time), nocturnal sleep duration, daytime napping.

    Main Outcomes and Measures: The primary outcomes were prevalence of obesity, specified as general obesity, defined as body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) of 30 or greater, and abdominal obesity, defined as waist circumference greater than 102 cm for men or greater than 88 cm for women. Multilevel logistic regression models with random effects for study centers were performed to calculate adjusted odds ratios (AORs) and 95% CIs.

    Results: Overall, 136 652 participants (81 652 [59.8%] women; mean [SD] age, 51.0 [9.8] years) were included in analysis. A total of 27 195 participants (19.9%) had general obesity, and 37 024 participants (27.1%) had abdominal obesity. The mean (SD) nocturnal sleep duration was 7.8 (1.4) hours, and the median (interquartile range) midsleep time was 2:15 am (1:30 am-3:00 am). A total of 19 660 participants (14.4%) had late bedtime behavior (ie, midnight or later). Compared with bedtime between 8 pm and 10 pm, late bedtime was associated with general obesity (AOR, 1.20; 95% CI, 1.12-1.29) and abdominal obesity (AOR, 1.20; 95% CI, 1.12-1.28), particularly among participants who went to bed between 2 am and 6 am (general obesity: AOR, 1.35; 95% CI, 1.18-1.54; abdominal obesity: AOR, 1.38; 95% CI, 1.21-1.58). Short nocturnal sleep of less than 6 hours was associated with general obesity (eg, <5 hours: AOR, 1.27; 95% CI, 1.13-1.43), but longer napping was associated with higher abdominal obesity prevalence (eg, ≥1 hours: AOR, 1.39; 95% CI, 1.31-1.47). Neither going to bed during the day (ie, before 8pm) nor wake-up time was associated with obesity.

    Conclusions and Relevance: This cross-sectional study found that late nocturnal bedtime and short nocturnal sleep were associated with increased risk of obesity prevalence, while longer daytime napping did not reduce the risk but was associated with higher risk of abdominal obesity. Strategic weight control programs should also encourage earlier bedtime and avoid short nocturnal sleep to mitigate obesity epidemic.

    Matched MeSH terms: Sleep Initiation and Maintenance Disorders/etiology*; Sleep Initiation and Maintenance Disorders/epidemiology
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