I wanted to look at the amount of tau in a region for a given level of amyloid and compare these values for males and females. I only had a single measurement for each participant. I took their tau scan, and the nearest corresponding amyloid scan. Here are the demographics of the cohort I analyzed:

##                   Stratified by GENDER
##                    female        male          p      test
##   n                   92            56                    
##   EDUC (mean (sd)) 16.15 (2.47)  16.27 (2.28)   0.777     
##   apoe4 = 1 (%)       28 (30.8)     17 (30.4)   1.000

For my analysis, I used a linear model of:

Regional Tau ~ Regional Amyloid + Sex + Sex*Amyloid + Education + APOE status.

This analysis shows results for only cognitively normal individuals. The results changed quite a bit when I dropped everyone with CDR > 0.

Only three regions show a significantly different rate of change between men and women; however, a ton of regions show different absolute levels when comparing men and women. I attempted to summarize these with the first figure.

The figure may be a bit difficult to interpret. It is the regression coefficient for regional amyloid. For a given level of tau, male participants will have more amyloid accumulated than female participants. For example, in the cuneus, if a man and woman have equivalent levels of tau, men will have nearly 20% more amyloid than women.

##                                Region  Interaction
## 20   PUP_fSUVR_rsf_TOT_CTX_FUSIFORM.x 0.0043477009
## 22   PUP_fSUVR_rsf_TOT_CTX_INFERTMP.x 0.0001044657
## 24 PUP_fSUVR_rsf_TOT_CTX_ISTHMUSCNG.x 0.0063410969

I was trying to synthesize Manu’s recent FDG paper and the Sperling amyloid-tau paper. If women are “3 years younger”, but also have a bunch more tau for a given level of amyloid…what do you do with that?

First I had to limit the analysis to just the people who had an FDG scan. This is a smaller subset of participants, but the cohorts are well matched. Remember, Everyone is cognitively normal in this analysis. 

##                   Stratified by GENDER
##                    female        male          p      test
##   n                   40            24                    
##   Age (mean (sd))  67.33 (6.45)  66.67 (6.86)   0.698     
##   EDUC (mean (sd)) 16.02 (2.63)  16.54 (2.69)   0.453     
##   apoe4 = 1 (%)        8 (20.5)      9 (37.5)   0.237

I don’t have any answers, but below I have visualized the correlations between amyloid and tau, amyloid and FDG, and tau and FDG for each region. Blue correlations are significant at p < 0.01. Red are not significant.

The most interesting thing, I think, is how many regions have tau correlated with amyloid for women, but not for men.

For FDG, it looks like there are a few regions where high levels of amyloid impede brain metabolism in women, but not in men. On the contrary, there are a few regions where high levels of tau are correlated with high levels of brain metabolism for men, but not in women.