The Promise of the State Space Approach to Time Series Analysis for Nursing Research

Abstract

Background Nursing research, particularly related to physiological development, often depends on the collection of time series data. The state space approach to time series analysis has great potential to answer exploratory questions relevant to physiological development but has not been used extensively in nursing. Objectives To introduce the state space approach to time series analysis and demonstrate potential applicability to neonatal monitoring and physiology. Method We present a set of univariate state space models; each one describing a process that generates a variable of interest over time. Each model is presented algebraically and a realization of the process is presented graphically from simulated data. This is followed by a discussion of how the model has been or may be used in two nursing projects on neonatal physiological development. Results The defining feature of the state space approach is the decomposition of the series into components that are functions of time; specifically, slowly varying level, faster varying periodic, and irregular components. State space models potentially simulate developmental processes where a phenomenon emerges and disappears before stabilizing, where the periodic component may become more regular with time, or where the developmental trajectory of a phenomenon is irregular. Discussion The ultimate contribution of this approach to nursing science will require close collaboration and cross-disciplinary education between nurses and statisticians.

The Association Between Very Premature Infant Body Temperatures Over Time and Respiratory Care

“…This exploratory, mixed-methods, correlational study was a secondary analysis of 12 VLBW infants from the parent study (NIH/NINR: 1R15NR012157-01, RWJF: 68041), “Body Temperature and Vasomotor Tone in Preterm Infants” (Knobel et al, 2011; Knobel-Dail et al, 2016, 2017; Levy et al, 2012). The parent study was designed to examine vasomotor tone maturation, as well as morbidity and mortality associated with this maturation in very premature infants.…”

A Pilot Study to Examine Maturation of Body Temperature Control in Preterm Infants

“…The statistical approach used to examine research questions related to maturation of control over central and peripheral body temperature was developed with the pilot data over approximately 1 year, with trial attempts at modeling data. Temperature data were modeled initially with logistic regression and then subsequently with the state space approach to time‐ series analysis (Durbin & Koopman, ; Levy, Elser, & Knobel, ). The resulting statistical methods identified long‐ term trends in maturation as well as shorter periods of abnormal perfusion.…”

“…Consequently, we were able to more clearly discern time periods where the infant kept the foot warmer than the abdomen, which is representative of an abnormal perfusion state—either due to immature neural control over blood flow, or physiologic instability causing an abnormal perfusion state. The analysis provides an excellent way to view the data and examine CP temperature differences over time (Levy et al., ).…”