Decrease in scale invariance of activity fluctuations with aging and in patients with suprasellar tumors

Figures & data

Table 1. Clinical characteristics.

	Healthy participants (n = 72)	NFMA patients (n = 68)	Craniopharyngioma patients (n = 22)
Age (years)	55.5 (44.0–64.0)	59.4 (51.5–63.5)	51.7 (33.3–62.1)
Women	34 (47.2%)	33 (48.5%)	7 (31.8%)
BMI (kg/m^2)	26.2 (23.4–29.8)	27.2 (25.3–29.5)	28.9 (25.8–32.6)*
Adjuvant radiotherapy		20 (29.4%)	7 (31.8%)
Preoperative VFD		53 (77.9%)	14 (63.6%)
Suprasellar extension^a		64 (94%)	22 (100%)
Hypopituitarism		56 (82.4%)	22 (100%)
ACTH deficiency		31 (45.6%)	18 (81.8%)
TSH deficiency		41 (60.3%)	22 (100%)
GH deficiency		49 (72.1%)	20 (90.9%)
LH/FSH deficiency		38 (55.9%)	19 (86.4%)
Vasopressin deficiency		7 (10.3%)	14 (63.6%)
Intradaily variability	0.35 (0.30–0.43)	0.40 (0.34–0.50)**	0.38 (0.34–0.51)
Interdaily stability	0.84 (0.76–0.89)	0.80 (0.68–0.84)*	0.78 (0.67–0.87)
Activity during wake (counts)^b	254 (211–323)	243 (194–280)	236 (215–295)

Data represent median (interquartile range) or number (percentage). ^aHardy–Wilson classification (Hardy, 1979) minimal II-B. ^bAverage activity per minute during hours spend awake in counts, each count representing 0.04 g of wrist acceleration per second. NFMA: nonfunctioning pituitary macroadenoma. VFD: visual field defects. *p < 0.05 or **p < 0.01 compared to healthy subjects.

Table 2. Associations with the scaling exponent α.

	B	95% CI	p-Value
α2 at time scales 1.5–10 h
Disease	−0.074	−0.114–−0.034	0.014
Disease*gender	−0.068^a	−0.113–−0.024	0.010
Age*activity levels	0.003^b,c	0.001–0.006	0.021
Only in patients
Radiotherapy*activity levels	0.041^b	0.012–0.070	0.019
∆ = α1–α2
Disease	0.058	0.016–0.099	0.006
α3 at time scales 10–24 h
Age	0.193^c	0.066–0.320	0.003
Activity levels	0.472^b	0.197–0.747	0.001
Age*activity levels	−0.069^b,c	−0.021–−0.116	0.004

Data represented factors included in the linear regression model that were best able to predict scaling exponent α at different time scales. ^aI.e., the disease effect is stronger in men than women. ^bB for higher activity level: increase of 100 counts per 1-minute epoch. ^cB for age: increase of 10 years. *: interaction. Disease: NFMA or craniopharyngioma.

Figure 1. Average detrended fluctuation functions F(n) from locomotor activity data of 72 healthy controls, 68 NFMA patients and 22 craniopharyngioma patients. Data are shown on log-log plots and curves are vertically shifted in [A] for better visualization of differences between groups (vertical offset does not alter the slope). The scaling behavior can be separated in three time scale regions based on two breakpoints at ~1.5 h and ~10 h. The break points can be seen more clearly when F(n) is divided by time scale n in [B], indicating the change in F(n) per time unit n. The straight lines represent perfect scale-invariance α = 1.00 [A] or α’ = 0.00 [B].

Figure 2. Scaling exponent α in 72 healthy controls, 68 NFMA patients and 22 craniopharyngioma patients (CP), obtained from detrended fluctuation analysis, separated in three time scale (n) regions of the 24-h analysis period. The dotted lines represent too much randomness or white noise at α = 0.5, too much regularity or red noise at α = 1.5, and the delicate balance between the two in healthy systems known as complex scale invariance or pink noise at α = 1.0. Bars represent mean ± SD.

Figure 3. Scaling exponent α₂ (times scales 1.5–10 h) in 72 healthy subjects and 90 patients (NFMA and craniopharyngioma). Data are separated by gender and in four age groups. In healthy subjects, group size for each age group in men is 3, 8, 11 and 16, and for women 3, 7, 19 and 5. For patients, group size for each age group in men is 3, 9, 25 and 13, and for women 4, 6, 21 and 9. The dotted line represents complex scale invariance with α = 1.0. Boxes display the 25th, 50th and 75th percentile, bars the 10th and 90th percentile and dots the outliers.

Hardy J .1979 .The transsphenoidal surgical approach to the pituitary .Hosp Pract. 14:81–89.

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