title: Cosinor analysis for temperature time series data of long duration.
abstract: The application of cosinor models to long time series requires special attention. With increasing length of the time series, the presence of noise and drifts in rhythm parameters from cycle to cycle lead to rapid deterioration of cosinor models. The sensitivity of amplitude and model-fit to the data length is demonstrated for body temperature data from ambulatory menstrual cycling and menopausal women and from ambulatory male swine. It follows that amplitude comparisons between studies cannot be made independent of consideration of the data length. Cosinor analysis may be carried out on serial-sections of the series for improved model-fit and for tracking changes in rhythm parameters. Noise and drift reduction can also be achieved by folding the series onto a single cycle, which leads to substantial gains in the model-fit but lowers the amplitude. Central values of model parameters are negligibly changed by consideration of the autoregressive nature of residuals.
authors.affiliation: Center for Nursing Research at University of Texas School of Nursing at Houston, Houston, Texas 77225-0334, USA. Nikhil.S.Padhye@uth.tmc.edu
authors.forename: Nikhil S
authors.initials: NS
authors.lastname: Padhye
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Hanneman
mesh_terms: D000328:Adult; D000818:Animals; D015982:Bias; D002940:Circadian Rhythm / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008593:Menopause / Q000502:physiology*; D008597:Menstrual Cycle / Q000502:physiology*; D008875:Middle Aged; D023421:Models, Animal; D015233:Models, Statistical; D008991:Monitoring, Physiologic; D012680:Sensitivity and Specificity; D012881:Skin Temperature / Q000502:physiology*; D013552:Swine; D013997:Time Factors; D014432:Tympanic Membrane / Q000502:physiology