Published\In Press

  1. 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. 2017.
  2. 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; 106: 233-235.
  3. 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; 101: 102-108.
  4. 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; 2 (2): e150.

Under Review\Revision

  1. 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. Under review PLoS ONE.
  2. Zipunnikov, V., Dey, D., Leroux, A., Di, J., Urbanek, J., Harris, T., and Crainiceanu, C.. Objectively measured late-morning physical activity predicts mortality in the NHANES 2003-2006 cohorts. Resubmitted to PLoS ONE after revision.
  3. Johns, J., Di, J., Merikangas, K., Cui, L., Swendsen, J., and Zipunnikov, V.. Fragmentation as a novel measure of stability in normalized trajectories of mood and attention assessed by electronic diaries. Under review Physiological Measurement.
  4. Grigsby, M., Di, J., Leroux, A., Zipunnikov, V., Xiao, L., Crainiceanu, C., and Checkley, W.. Novel Metrics for Growth Model Selection. Resubmitted to Emerging Themes in Epidemiology after revision.
  5. Di, J., Spira, A., Bai, J., Urbanek, J., Leroux, A., Wu, M., Resnick, S., Simonsick, E., Ferrucci, L., Schrack, J., and Zipunnikov, V.. Joint and individual representation of domains of physical activity, sleep, and circadian rhythmicity. Under review Statistics in Biosciences.
  6. Leroux, A., Di, J., Smirnova, E., Mcguffey, E., Cao, Q., Bayatmokhtari, E., Tabacu, L., Zipunnikov, V., Urbanek, J., Crainiceanu, C.. Organizing and analyzing the activity data in NHANES. Under review Statistics in Biosciences.

In Preparation

  1. Generalized singular value decompositions based on higher order interactions (GSVD).


  1. actigraphy. (R package). Feature extraction for minute level actigraphy data. [Github].