There was no significant effect of diagnosis on intensity (F(1,91) = 0.10, p = 0.75). Age was, however, significantly related to intensity overall (F(1,91) = 5.08, p = 0.027), and, in particular, within regions 1 (F(1,91) = 17.29, p = 0.0001) and 2 (F(1,91) = 5.20, p = 0.025). Age was not significantly related to intensity in regions 4 and 5, and there was no significant segment x diagnosis effect on intensity.
Since the age effect in region 1 was so pronounced, we decided to compute polynomial regression coefficients in order to characterise the age progression in this region. The linear relationship between age and intensity in the pooled data was significant (t(92) = 4.14, p = 0.001), but higher-degree terms did not contribute significantly to the fit. Regression models for the patient and control groups were quite similar to the pooled model, again showing only a significant linear relationship between age and intensity, with little difference between groups in slope or intercept.
