White matter lesions characterise brain involvement in moderate to severe chronic obstructive pulmonary disease, but cerebral atrophy does not

Table 2 Group differences in whole-brain measures

	Controls (N = 24)		Patients (N = 31)		Difference
	Mean (median)	SD (IQR)	Mean (Median)	SD (IQR)	Statistic	p
Grey Matter Volume (% TIV)	(25.20)	(2.20)	(25.01)	(1.45)	−0.1206²	0.9030²
White Matter Volume (% TIV)	27.07	2.26	27.35	1.50	0.9757¹	0.3279¹
Total Intracranial Volume (cm³)	1427	81	1400	99	2.6189¹	0.1118¹
Tissue Volume Ratio	0.52	0.03	0.53	0.02	0.7884¹	0.3788¹
Average Cortical Thickness (mm)	(2.21)	(1.38)	(2.28)	(0.26)	−0.1141²	0.9060²

Group comparisons of normalised whole-brain measures. Age and gender were included as covariates in all models; total intracranial volume was also included for the average cortical thickness model. For Gaussian data, group means and standard deviations (SD) are presented. For non-Gaussian data (brackets), group medians and interquartile ranges (IQR), are presented. Statistical tests include ¹ANCOVAs of showing F-statistics and p-values and ²permutation general linear models (10000 permutations) for which t-statistics and p-values (p) are displayed

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