Hi Foad,

if all subjects have 2 time point and same time delta, you can compute the difference between time points, divide by 2 (for yearly change) and run a standard GLM analysis on that measure instead of thickness.

Or you can model this with linear mixed effects models (which makes sense if time deltas are very different or if you have different many time points per subject).

Best, Martin

On 20. Aug 2018, at 22:27, Foad Taghdiri foad.taghdiri@mail.utoronto.ca wrote:

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Hello,

I have done freesurfer (v6) longitudinal preprocessing for 20 subjects (baseline and 2-year follow-up). We also have levels of some blood biomarkers (e.g. tau, neurofilament light) for these subjects at the baseline. I am interested to figure out if the level of blood biomarkers at the baseline is related to the amount of cortical thinning over time, and if so, which brain regions’ cortical thinning are significantly correlated with the blood biomarker. I was wondering if you could please guide me through this analysis and let me know how I can do it.

Thanks Best, Foad

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