Assessing recurrence of depression using a zero-inflated negative binomial model: A secondary analysis of lifelog data

•It is important to avoid false-negatives in diagnosis of recurrent depression.•Daily hours of sitting idly increased the chances of recurrent depression two or four weeks later.•Change in exposure to daily ultraviolet light from non-exposure reduced recurrent depression.•Daily hours of sitting idly can contribute to accurate measurement of recurrent depression. When studying recurrence of depression, researchers should pay attention to cases where physicians' assessment corresponds to the patients' perception. However, they should also focus on potential signs of recurrence when the recurrence is suspected by the physicians but not the patients (false-negative zeros). Because false negatives can delay diagnosis and treatment, we aimed to investigate “sitting idly” as a predictor influencing no alert sign of recurrence and estimated the counts of recurrence of depression. A smartphone application and a wearable device were used to collect lifelog data from 89 remitted depressive patients over one year. Recurrent depression was defined using the Japanese version of the Kessler Psychological Distress Scale and Patient Health Questionnaire-9 scores. Estimates of the population-averaged parameters indicated that daily hours of sitting idly increased the chances of recurrent depression occurring two to four weeks later. Exposure to daily ultraviolet light reduced depression relapse. Although long sleep was a determinant of zero outcome of the recurrence of depression after two to four weeks, daily hours of sitting idly can negate it. Thus, daily hours of sitting idly could reduce overdispersion of the recurrence of depression, and we could measure recurrent depression accurately by considering changes in sitting idly.