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Figures
- Fig. 1
Example of the tracts between the left thalamus and the left pars triangularis. The olive-coloured region of interest indicates grey matter and white matter of the thalamus. The red region of interest indicates grey matter and white matter of the left pars triangularis. (A) Sagittal view. (B) Axial view.
- Fig. 2
Group differences in diffusion measures of the tracts connecting the left thalamus and the left pars triangularis. Blue dots represent controls, and red rectangles represent patients with insomnia disorder. Blue bars (controls) and red bars (insomnia disorder) represent the mean ± standard deviation. Blue and red triangles denote outliers. Significant group differences in diffusion measures of the left thalamus–pars triangularis white-matter tracts were found in fractional anisotropy and axial diffusivity values. Data that were 1.5 × interquartile range below Q1 (lower quartile) or above Q3 (upper quartile) were removed from the analyses. *Significant group differences (p < 0.05).
Tables
Group; mean ± SD* Statistical tests† Variables Control (n = 27) Insomnia disorder (n = 22) t or χ2 df p value Age, yr 33.4 ± 7.2 37.5 ± 10.5 t = 1.618 47 0.11 Sex, female, no. (%) 16 (59.3) 12 (54.5) χ2 = 0.110 1 0.74 Duration of insomnia disorder, yr ― 5.3 ± 5.9 Pittsburgh Sleep Quality Index Total score 2.4 ± 1.3 12.3 ± 3.4 t = 12.925 25.680 < 0.001 Total sleep time, min 437.0 ± 44.9 254.6 ± 98.0 t = −8.074 28.131 < 0.001 Sleep efficiency, % 95.2 ± 4.5 62.0 ± 21.2 t = −7.228 22.517 < 0.001 Insomnia Severity Index score 1.4 ± 1.8 18.2 ± 5.4 t = 13.998 24.996 < 0.001 Epworth Sleepiness Scale score 3.82 ± 2.9 6.96 ± 3.8 t = −3.265 47 0.002 Dysfunctional Beliefs and Attitutes About Sleep score 57.3 ± 20.2 97.0 ± 22.5 t = 6.489 47 < 0.001 Beck Depression Inventory (non-sleep score)‡ 2.0 ± 2.1 8.7 ± 4.4 t = −6.485 26.534 < 0.001 Neuropsychological data of CANTAB SOC, mean initial thinking time (5 moves), s 5064.48 ± 3448.58 5632.02 ± 5989.57 t = −0.416 47 0.68 SOC, mean subsequent thinking time (5 moves), s 1367.21 ± 2432.04 2634.85 ± 4485.00 t = −1.261 47 0.21 SOC, problems solved in minimal moves 7.7 ± 1.2 6.6 ± 1.8 t = 2.499 34.663 0.017 Polysomnographic data Total sleep time, min 390.9 ± 58.9 323.8 ± 60.2 t = −3.935 47 < 0.001 Sleep latency, min 5.4 ± 3.8 16.9 ± 14.1 t = 3.750 23.474 0.001 Sleep efficiency, % 94.5 ± 3.2 80.3 ± 9.3 t = −6.874 25.043 < 0.001 Wake after sleep onset, min 18.4 ± 14.3 64.6 ± 43.4 t = 4.779 24.708 < 0.001 Apnea–Hypopnea Index, n per h 2.4 ± 1.6 2.8 ± 1.7 t = 0.872 47 0.39 Total arousal index, n per h 5.3 ± 1.5 10.0 ± 4.3 t = 4.921 25.402 < 0.001 Stage N1 4.4 ± 2.8 15.5 ± 4.8 t = 10.077 47 < 0.001 Stage N2 52.1 ± 9.1 49.5 ± 7.7 t = −1.068 47 0.29 Stage N3 18.4 ± 6.6 12.2 ± 6.6 t = −3.260 47 0.002 Stage R 25.1 ± 4.9 22.9 ± 4.1 t = −1.719 47 0.092 CANTAB = Cambridge Neuropsychological Test Automated Battery; SD = standard deviation; SOC = Stockings of Cambridge from the Cambridge Neuropsychological Test Automated Battery.
↵* Unless otherwise specified.
↵† Statistical tests were performed using the Student t test (for equal variance) or Welch t test (for unequal variance).
↵‡ Beck Depression Inventory (non-sleep score): excluding the sleep item (16) from the total Beck Depression Inventory 21-item score.
- Table 2
Group differences in diffusion measures of the tracts connecting the left thalamus and the left pars triangularis*
Group; mean ± SD Statistical tests† Statistical tests‡ Variables Control (n = 27) Insomnia disorder (n = 22) t df pFDR F df pFDR Fractional anisotropy (10−3) 520.32 ± 29.00 485.95 ± 43.76 2.913 45 0.022 8.647 1,43 0.02 Radial diffusivity (10−3 mm2/s) 458.58 ± 26.33 481.20 ± 39.63 −1.337 44 0.25 0.897 1,42 0.47 Axial diffusivity (10−3 mm2/s) 1174.59 ± 42.90 1140.90 ± 47.29 2.316 46 0.05 5.895 1,44 0.038 Trace (10−3 mm2/s) 2.09 ± 0.67 2.10 ± 0.86 −0.345 41 0.73 0.056 1,39 0.81 FDR = false discovery rate; SD = standard deviation.
↵* Diffusion measures 1.5 × interquartile range below Q1 (lower quartile) or above Q3 (upper quartile) were removed in all analyses.
↵† Group differences in each diffusion measure using Student’s t-test.
↵‡ Adjusted for age and sex; analysis of covariance was performed to reveal group differences in each diffusion measure.
- Table 3
Group differences in the structural variables of the left thalamus and the pars triangularis*
Group; mean ± SD Statistical tests† Statistical tests‡ Variables Control (n = 27) Insomnia disorder (n = 22) t df pFDR F df pFDR Pars triangularis Volume, mm3 3107.10 ± 512.07 2802.36 ± 37.62 2.209 47 0.05 5.782 1,45 0.048 Adjusted volume§ 0.00239 ± 0.00048 0.00202 ± 0.00031 3.236 45.001 0.014 14.322 1,45 0.003 Surface area, mm2 1322.78 ± 189.98 1189.45 ± 169.25 2.564 47 0.044 6.911 1,45 0.041 Grey matter thickness, mm 2.46 ± 0.15 2.46 ± 0.17 0.105 47 0.92 0.368 1,45 0.55 Grey matter volume, mm3 3725.22 ± 592.80 3349.82 ± 460.49 2.431 47 0.044 4.406 1,45 0.06 Thalamus Volume, mm3 8699.79 ± 1129.52 8402.70 ± 1101.21 0.926 47 0.42 1.099 1,45 0.35 Adjusted volume§ 0.00665 ± 0.00093 0.00605 ± 0.00061 2.158 45 0.05 4.62 1,43 0.058 FDR = false discovery rate; SD = standard deviation.
↵* Structural measures 1.5 × interquartile range below Q1 (lower quartile) or above Q3 (upper quartile) were removed in all analyses.
↵† Group differences in each diffusion measure using a Student’s t-test (for equal variance) or Welch’s t-test (for unequal variance).
↵‡ Adjusted for age and sex; analysis of covariance was performed to reveal group differences in structural variables.
↵§ Adjusted volume was defined as each region of interest volume divided by intracranial volume.
- Table 4
Correlations between clinical or polysomnographic data and diffusion measures connecting the left thalamus and the left pars triangularis in patients with insomnia
Fractional anisotropy Radial diffusivity Axial diffusivity Variables r p r p r p Insomnia duration, yr −0.218 0.33 0.142 0.53 −0.217 0.33 Epworth Sleepiness Scale score −0.318 0.15 0.437 0.042 0.017 0.94 Insomnia Severity Index score 0.254 0.25 −0.183 0.41 0.210 0.35 Dysfunctional Beliefs and Attitudes About Sleep score 0.186 0.41 −0.238 0.29 −0.067 0.77 Pittsburgh Sleep Quality Index score 0.279 0.21 −0.261 0.24 0.167 0.46 Beck Depression Inventory (non-sleep score)* 0.018 0.94 −0.037 0.87 −0.028 0.90 Neuropsychological test data SOC, problems solved in minimal moves 0.451 0.034 −0.348 0.11 0.355 0.11 Polysomnographic data Total sleep time, min −0.046 0.84 −0.056 0.80 −0.115 0.61 Sleep efficiency, % −0.237 0.29 0.280 0.21 −0.006 0.98 SOC = Stockings of Cambridge from the Cambridge Neuropsychological Test Automated Battery.
Statistical analyses were performed using Pearson’s r correlation.
↵* Beck Depression Inventory (non-sleep score): excluding the sleep item (16) from the total Beck Depression Inventory 21-item score.
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