• TRA keeps contact with twins, enabling prospective longitudinal studies
• Twins were studied when they were adolescents and followed into adulthood
• Response lower when they were in the 20s, but increased when they moved into their 30s
• Qualitative study of uptake of, and committed, smoking using ~20 discordant pairs
• Twins’ natural life histories are gold for research
• Analytic approach
• – Multilevel models
  
  • Observations on individuals within twin pairs
  • Extension of variance components models

          – Trajectory model

•  Estimate growth curve and assess association of classes of curve with outcome

References
Hopper, J. L., Foley, D. L., White, P. A. and Pollaers, V. (2013). Australian Twin Registry: 30 Years Of Progress, Twin Research and Human Genetics, 16, 34-42.

Gatz, M., Harris, J. R., Kaprio, J., McGue, M., Smith, N. L., Snieder, H., Spiro, A. and Butler, D. A. (2015). Cohort Profile: The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry), International Journal of Epidemiology, 44(3), 819-25.

Grantz, K. L., Grewal, J., Albert, P. S., Wapner, R., D'Alton, M. E., Sciscione, A., Grobman, W. A., Wing, D. A., Owen, J., Newman, R. B., Chien, E. K., Gore-Langton, R. E., Kim, S., Zhang, C., Buck Louis, G. M. and Hediger, M. L.(2016). Dichorionic Twin Trajectories: The NICHD Fetal Growth Studies, American Journal of Obstetrics andGynecology, 215, 221.e1-.e16.

Loke, Y. J., Novakovic, B., Ollikainen, M., Wallace, E. M., Umstad, M. P., Permezel, M., Morley, R., Ponsonby, A. L., Gordon, L., Galati, J. C., Saffery, R. and Craig, J. M.. (2013). The Peri/postnatal Epigenetic Twins Study (PETS), Twin Research and Human Genetics, 16(1), 13-20.

Moayyeri, A., Hart, D. J., Snieder, H., Hammond, C. J., Spector, T. D. and Steves, C. J. (2016). Ageing Trajectories in Different Body Systems Share Common Environmental Etiology: The Health Aging Twin Study (HATS), Twin Research and Human Genetics, 19, 27-34.