Sujata Saha

Bio: Sujata Saha is an academic researcher. The author has contributed to research in topics: Supply chain & Actigraphy. The author has an hindex of 4, co-authored 7 publications receiving 43 citations.

Pre-pandemic sleep behavior and adolescents' stress during Covid-19: a prospective longitudinal study

Abstract: Objective To prospectively document changes in adolescents' sleep before versus during the COVID-19 pandemic, and to examine their impact on adolescents' perceived stress. Methods Sixty-two typically developing adolescents participated in the study before (Time 1: January 15 to March 13, 2020) and during (Time 2: May 15 to June 30, 2020) the COVID-19 pandemic in Canada. At Time 1, each participant's sleep pattern was assessed in the home environment using actigraphy and sleep logs for seven consecutive nights. Adolescents completed a battery of questionnaires in which they reported on their sleep schedule, duration, and quality, as well as their activities at bedtime, their daytime sleepiness, and their social/emotional behavior. The participants' parents provided demographic information. At Time 2, each participant completed a sleep log, the same battery of questionnaires regarding sleep, and the Perceived Stress Scale. Results (1) Adolescents' reported sleep was of longer duration and on a delayed schedule during the COVID-19 pandemic compared to pre-pandemic. (2) A larger proportion of adolescents reported meeting or exceeding the recommended amount of sleep during the COVID-19 pandemic compared to pre-pandemic sleep. (3) "Social jet lag" disappeared during the COVID-19 pandemic. (4) A shorter reported sleep duration and higher level of arousal at bedtime at Time 1 were significant predictors of adolescents' perceived stress at Time 2-during the COVID-19 pandemic. (5) A higher levels of arousal at bedtime and lower reported sleep quality at Time 2 were concurrently associated with higher levels of perceived stress among adolescents, even when we controlled for the levels of pre-pandemic emotional or behavioral issues, sleep duration, or sleep quality. Conclusion Sleep duration and cognitive-emotional arousal, which are both modifiable behaviors, were associated with adolescents' perceived stress during the COVID-19 pandemic. These behaviors could be useful targets for preventive interventions aiming to reduce adolescents' stress in the face of stressogenic situations, such as the COVID-19 pandemic.

Two-echelon Supply Chain Model for Deteriorating Items in an Imperfect Production System with Advertisement and Stock Dependent Demand under Trade Credit

Abstract: This article presents a two-echelon supply chain model for deteriorating items, consisting of a single manufacturer and a single retailer, where the customer's demand to the retailer depends on advertisement and the displayed stock level of the retailer. Due to the imperfect production system, the manufacturer produces a certain quantity of defective items with the perfect products. The manufacturer inspects all the products immediately after production and sells the ideal quality items to the retailer. To entice the retailer to purchase more products, the manufacturer offers the retailer a trade-credit policy so that the retailer can get a chance to settle his account before the payment for the products. We have developed a cost function of this model. Numerical examples have been presented to clarify the applicability of this model and the sensitivity analysis with respect to different parameters involved with the model has been performed to study the effect of the parameter change on the decision variables.

A supply chain model under return policy considering refurbishment, learning effect and inspection error

Abstract: This article presents a three-echelon supply chain model consisting of a supplier, manufacturer, and a retailer, considering the return contract between the manufacturer and the retailer. Here, the manufacturer has two adjacent production units - the main production unit and a refurbishment unit. The main production unit of the manufacturer is imperfect, which produces an admixture of perfect and defective items. He inspects all the products immediately after production and sells good quality items to the retailer. The retailer receives a proportion of faulty products from him due to his erroneous inspection process, which he returns after inspection. The manufacturer sends all the defective products received from the retailer and the main production unit to the refurbishment unit for reworking. Moreover, the learning effect of the employees on the production cost is considered. Under these circumstances, the cost functions of each of the supply chain players have been derived. Finally, the applicability of the proposed model has been shown using a numerical example. The sensitivity analysis has been presented to study the effect of the parameters on the optimum decision variables.

A Multi-Storehouse Supply Chain Considering Systems’ Reliability and Free Shipping

Abstract: This paper aims to frame a two-player supply chain model with a production system's reliability influenced products’ defection rate. Upon generating and inspecting the products, the producer reworks the defectives and sells the perfect and reworked items to a retailer providing him free products' delivery. The retailer stores both types of commodities in the respective showrooms of finite capacities and keeps the excess conforming products in a leased warehouse. Eventually, the formulation of these two partners' profit functions performed, and a numerical illustration demonstrates this model's applicability. Results shows, hiring a storehouse is profitable for the retailer and the deterioration of the production system’s reliability impacts adversely on the manufacturer's profit.

Prospective Examination of Adolescent Sleep Patterns and Behaviors Before and During COVID-19.

Abstract: Study objectives To prospectively examine changes in adolescent sleep before and during the COVID-19 pandemic in adolescents with and without ADHD. Methods Participants were 122 adolescents (ages 15-17; 61% male; 48% with ADHD). Parents reported on adolescents' sleep duration and difficulties initiating and maintaining sleep (DIMS); adolescents reported on sleep patterns, sleep duration, delayed sleep/wake behaviors, and daytime sleepiness before (September 2019-February 2020) and during (May-June 2020) COVID-19. Adolescents also reported on their health behaviors, COVID-19-related negative affect, and difficulties concentrating due to COVID-19. Results Parents reported adolescents had more DIMS during COVID-19 than before COVID-19, with clinically-elevated rates increasing from 24% to 36%. Both bedtimes and waketimes shifted later during COVID-19, and adolescents reported more delayed sleep/wake behaviors. Adolescents also reported less daytime sleepiness and longer school night sleep duration during COVID-19. In considering differences between adolescents with and without ADHD, adolescents with ADHD did not experience an increase in school night sleep duration and were less likely to obtain recommended sleep duration during COVID-19. In the full sample, controlling for ADHD status, COVID-19-related sadness/loneliness was associated with increases in DIMS, and spending less time outside and more COVID-19-related worries/fears were associated with increases in delayed sleep/wake behaviors during COVID-19. Conclusions COVID-19 had negative and positive impacts on adolescent sleep. Adolescents with ADHD did not experience the benefit of increased school night sleep duration during COVID-19 like adolescents without ADHD. Negative affect and health behaviors may be useful intervention targets for reducing negative impacts of COVID-19 for adolescent sleep.

Impact of the COVID-19 pandemic on elementary schoolers' physical activity, sleep, screen time and diet: A quasi-experimental interrupted time series study.

Abstract: Background COVID-19 school closures pose a threat to children's wellbeing, but no COVID-19-related studies have assessed children's behaviours over multiple years . Objective To examine children's obesogenic behaviours during spring and summer of the COVID-19 pandemic compared to previous data collected from the same children during the same calendar period in the 2 years prior. Methods Physical activity and sleep data were collected via Fitbit Charge-2 in 231 children (7-12 years) over 6 weeks during spring and summer over 3 years. Parents reported their child's screen time and dietary intake via a survey on 2-3 random days/week. Results Children's behaviours worsened at a greater rate following the pandemic onset compared to pre-pandemic trends. During pandemic spring, sedentary behaviour increased (+79 min; 95% CI = 60.6, 97.1) and MVPA decreased (-10 min, 95% CI = -18.2, -1.1) compared to change in previous springs (2018-2019). Sleep timing shifted later (+124 min; 95% CI = 112.9, 135.5). Screen time (+97 min, 95% CI = 79.0, 115.4) and dietary intake increased (healthy: +0.3 foods, 95% CI = 0.2, 0.5; unhealthy: +1.2 foods, 95% CI = 1.0, 1.5). Similar patterns were observed during summer. Conclusions Compared to pre-pandemic measures, children's PA, sedentary behaviour, sleep, screen time, and diet were adversely altered during the COVID-19 pandemic. This may ultimately exacerbate childhood obesity.