Selected Publications

  1. Schrack, J., Kuo, P., Wanigatunag, A., Di, J., Simonsick, EM., Spira, A., Ferrucci, L., and Zipunnikov, V.. Active-to-sedentary behavior transition, fatigability, and physical functioning in older adults. The Journal of Gerontology: Series A. 2018.
  2. Grigsby, M., Di, J., Leroux, A., Zipunnikov, V., Xiao, L., Crainiceanu, C., and Checkley, W.. Novel metrics for growth model selection. Emerging Themes in Epidemiology. 2018.
  3. Urbanek, J., Spira, A., Di, J., Leroux, A., Crainiceanu, C., and Zipunnikov, V.. Epidemiology of objectively measured bedtime and chronotype in US adolescents and adults: NHANES 2003 - 2006. Chronobiology International. 2018.
  4. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Total volume of physical activity: TAC, TLAC, or TAC(\(\lambda\)). Preventive Medicine. 2018.
  5. Di, J., Leroux, A., Urbanek, R., Varadhan, J., Spira, A., Schrack, J., and Zipunnikov, V.. Patterns of sedentary and active time accumulation are associated with mortality in US adults: The NHANES study. bioRxiv: 182337.
  6. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Re-evaluating the effect of age on physical activity over the lifespan. Preventive Medicine. 2017..
  7. Di, J., Li, Y., Friedman, MR., Reddy, S., Surkan, PJ., Shoptaw, S., and Plankey, M.. Determining survey satisficing of online longitudinal survey data in the Multicenter AIDS Cohort Study using a Group-Based Trajectory Analysis. Journal of Medical Internet Research Public Health and Surveillance. 2016.

A full list of my publications can be found on my Google Scholar page.


  1. actigraphy. (R package). Feature extraction for minute level actigraphy data. [Github].
  2. cdHOTS. (R package). Construct and decompose higher order tensorian statistics. [Github]
  3. actigraphy-profiles. (R Shiny App). A visualization tool for displaying minute-level actigraphy profiles (More features to be online). [Github]