Research

Machine Learning:

In my MSc and PhD theses, I used artificial neural networks to delineate non-linear patterns in clinical data by combining Poisson regression model with neural networks (PRNN) to relax the traditional Poisson regression assumption of linearity.  The theoretical aspect of this novel model was published in a methodological journal (Neural Computing and Application, 2009). This model contributed to new understanding of the role of androgens in coronary artery disease. Results revealed, a non-linear association of testosterone levels with coronary artery disease for first time. (European Journal of Epidemiology, 2009). Furthermore, the performance and utility of the model was illustrated for predicting five-year changes in cognitive scores (in Alzheimer Disease), using the Canadian Study of Health and Aging data. (Journal of Applied Statistics, 2011)

In my postdoctoral training I developed and applied another machine learning method      (multi-state transition model) for cognitive functions assessment and healthy aging. The model was based on the Markov process with interpretable parameters which could be adjusted for covariates. The model can compute probabilities of improvements, stabilization, worsening and dying as a function of baseline and the covariates estimate according to modified Poisson model between two assessments. This novel multi-state transition model has brought me several opportunities for collaboration and publication, so far model were used and published in the top clinical and methodological journals such as Annals of Epidemiology 2010, 2011, 2013; and Statistical Methods in Medical Research, 2014.

More recently in clinical application, we applied machine learning and Artificial Intelligence methods in spinal cord injury to accommodate the non-linear nature of data.

A simplified clinical prediction rule for prognosticating independent walking after spinal cord injury: a prospective study from a Canadian multicenter spinal cord injury registry. (The Spine Journal, 2017)

Impact of Therapy on Recovery during Rehabilitation in Patients with Traumatic Spinal Cord Injury. (Journal of Neurotrauma, 2017)

Predicting Injury Severity and Neurological Recovery after Acute Cervical Spinal Cord Injury: A Comparison of Cerebrospinal Fluid and Magnetic Resonance Imaging Biomarkers. (Journal of Neurotrauma, 2018)

Unbiased Recursive Partitioning to Stratify Patients with Acute Traumatic Spinal Cord Injuries: External Validity in an Observational Cohort Study.                                    (Journal of Neurotrauma, 2019)

Highlighting discrepancies in walking prediction accuracy for patients with traumatic spinal cord injury: an evaluation of validated prediction models using a Canadian Multicenter Spinal Cord Injury Registry. (The Spine Journal, 2019)

Decision tree analysis to better control treatment effects in spinal cord injury clinical research. (The Journal of Neurosurgery, 2019)

A Novel Tool for Predicting One-year Mortality after Traumatic Spinal Cord Injury (submitted)

Development of an unsupervised machine learning algorithm for the prognostication of walking ability in spinal cord injury patients (submitted)

 Multi-state transition model

People with cognitive impairment can experience different degree of decline and not everybody declines at the same rate. It is known that a significant proportion of people can remain stable for a time or even improve. The previous statistical models mainly ignored these cases, or considered them as diagnosis misclassifications, measurement errors, or insignificant fluctuation. Earlier in 2006, Mitnitski, Bao and Rockwood (Mechanism of Aging and Development) described a multi-state transition model of change in health status during aging to address those problems. In our papers in PLoS ONE, 2008, 2009; Neuroepidemiology, 2009; Annals of Epidemiology 2010, 2011; Journal of the American Geriatrics Society, 2011; we developed and applied this model to cognitive functions and health. The model was based on the Markov process which could be adjusted for covariate.

See below link for more technical explanations:

about MSM

Reviewing Activities:

British Medical Journal (BMJ), Scientific Reports (Nature), Spinal Cord (Nature), BMC Geriatric, Neuroepidemiology, Clinical Endocrinology, Journal of Public Health, Journal of Applied Statistics, Neural Computing and Applications, Current Gerontology and Geriatric Research, Iranian Journal of Pathology