smartphones) commercial devices that contain accelerometers and are used primarily during the day, and recharged rather than used at night. in-bed) may also prove clinically useful, with applications to large-scale studies using new wearable (e.g. However, assessing midpoints based on non-sleep (daytime) activity intervals (e.g., out-of-bed vs. In our previous study, we assessed chronotypes based on objectively measured sleep intervals (e.g., in-bed vs. We found objective (actigraphy-derived) sleep interval midpoint values yielded reliable estimates comparable to self-reported chronotype. We recently published work investigating the utility of examining objective sleep interval midpoint values (based on wrist actigraphy) as a possible chronotype index, and its correlation with subjective chronotype (as measured by the CSM) ( Gershon et al., 2018). This could provide clinically useful additional information, beyond overall categorical classifications of morningness/eveningness. For example, wrist actigraphy, a common tool used to estimate sleep/wake patterns in sleep research, could characterize individual nights of sleep, and thus identify emerging changes in sleep timing patterns and in next-day emotional affect, incident mood episodes and other clinically important emergent psychiatric events, such as hospitalization.
Given the circadian rhythm irregularities inherent in BD, objective chronotype measurement could prove useful in providing enhanced chronotype data on a night-to-night basis. Smith et al., 1989 Zavada, Gordijn, Beersma, Daan, & Roenneberg, 2005), and have commonly found BD associated with greater eveningness (rather than morningness) chronotype relative to control groups ( Melo, Abreu, Linhares Neto, de Bruin, & de Bruin, 2017). Such categorizations have proven useful, have shown good psychometric properties (C. Smith, Reilly, & Midkiff, 1989), and the Munich Chronotype Questionnaire (MCTQ) ( Roenneberg et al., 2007)), to identify chronotypes. Traditionally, clinicians and researchers alike have relied upon self-report instruments (for example, the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) ( Horne & Östberg, 1976), the Composite Scale of Morningness (CSM) (C. In recognition of the importance of sleep and circadian rhythms for illness course and treatment, managing sleep and circadian rhythm irregularities in BD care has been a key target of therapeutic efforts-therapies such as Interpersonal and Social Rhythm Therapy ( Ehlers, Frank, & Kupfer, 1988 Frank, Swartz, & Kupfer, 2000) designed to stabilize circadian patterns, may thus mitigate mood fluctuations ( Frank, Swartz, & Boland, 2007).Īccurately identifying chronotype (i.e., eveningness or morningness preference) in BD patients could importantly enhance the efficiency of allocating appropriate therapeutic interventions. Abnormalities in sleep quality, as well as circadian rhythm irregularities, may be markers of current or imminent manic or depressive, episodes ( Cretu, Culver, Goffin, Shah, & Ketter, 2016 Gershon et al., 2017 Perlman, Johnson, & Mellman, 2006), or future positive or negative affect ( Kaufmann, Gershon, Eyler, & Depp, 2016), and therefore are important markers for monitoring BD course and treatment progress. When working with a sample, divide by the size of the data set minus 1, n - 1.Sleep disturbance is a pervasive and persistent phenomenon in bipolar disorder (BD), experienced by between 70–99% of BD patients ( Harvey, Talbot, & Gershon, 2009). When working with data from a complete population the sum of the squared differences between each data point and the mean is divided by the size of the data set, The formula for variance (s 2) is the sum of the squared differences between each data point and the mean, divided by the number of data points. Standard deviation of a data set is the square root of the calculated variance of a set of data. You can copy and paste lines of data points from documents such as Excel spreadsheets or text documents with or without commas in the formats shown in the table below.
You can also see the work peformed for the calculation. Click Calculate to find standard deviation, variance, count of data points This standard deviation calculator uses your data set and shows the work required for the calculations.Įnter a data set, separated by spaces, commas or line breaks. A high standard deviation indicates greater variability in data points, or higher dispersion from the mean. A low standard deviation indicates that data points are generally close to the mean or the average value. Standard deviation is a statistical measure of diversity or variability in a data set.
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