TY - JOUR
T1 - Fractal biomarker of activity in patients with bipolar disorder
AU - Knapen, Stefan E.
AU - Li, Peng
AU - Riemersma-Van Der Lek, Rixt F.
AU - Verkooijen, Sanne
AU - Boks, Marco P.M.
AU - Schoevers, Robert A.
AU - Scheer, Frank A.J.L.
AU - Hu, Kun
N1 - Funding Information:
Acknowledgements. This project has been supported by the Foundation ‘De Drie Lichten’ in The Netherlands. The cross-sectional study was funded by the National Institute of Mental Health (NIMH), Grant number: R01 MH090553. The NIMH had no role in the design and conduct of the study, collection, management, analysis, or interpretation of the data, preparation, review, or approval of the manuscript, and decision to submit the manuscript for publication. FAJLS was partially supported by NIH grants R01HL118601 and RF1AG059867. KH was partially supported by the NIH grants: R01AG048108, RF1AG059867, and RF1AG064312.
Funding Information:
Financial support. This project has been supported by the Foundation ‘De Drie Lichten’ in The Netherlands. The cross-sectional study was funded by the National Institute of Mental Health (NIMH), Grant number: R01 MH090553. The NIMH had no role in the design and conduct of the study, collection, management, analysis, or interpretation of the data, preparation, review, or approval of the manuscript, and decision to submit the manuscript for publication. FAJLS was partially supported by NIH grants R01HL118601 and RF1AG059867. KH was partially supported by the NIH grants: R01AG048108, RF1AG059867, and RF1AG064312.
Publisher Copyright:
Copyright © The Author(s), 2020. Published by Cambridge University Press.
PY - 2021/7
Y1 - 2021/7
N2 - BACKGROUND: The output of many healthy physiological systems displays fractal fluctuations with self-similar temporal structures. Altered fractal patterns are associated with pathological conditions. There is evidence that patients with bipolar disorder have altered daily behaviors.METHODS: To test whether fractal patterns in motor activity are altered in patients with bipolar disorder, we analyzed 2-week actigraphy data collected from 106 patients with bipolar disorder type I in a euthymic state, 73 unaffected siblings of patients, and 76 controls. To examine the link between fractal patterns and symptoms, we analyzed 180-day actigraphy and mood symptom data that were simultaneously collected from 14 patients.RESULTS: Compared to controls, patients showed excessive regularity in motor activity fluctuations at small time scales (<1.5 h) as quantified by a larger scaling exponent (α1 > 1), indicating a more rigid motor control system. α1 values of siblings were between those of patients and controls. Further examinations revealed that the group differences in α1 were only significant in females. Sex also affected the group differences in fractal patterns at larger time scales (>2 h) as quantified by scaling exponent α2. Specifically, female patients and siblings had a smaller α2 compared to female controls, indicating more random activity fluctuations; while male patients had a larger α2 compared to male controls. Interestingly, a higher weekly depression score was associated with a lower α1 in the subsequent week.CONCLUSIONS: Our results show sex- and scale-dependent alterations in fractal activity regulation in patients with bipolar disorder. The mechanisms underlying the alterations are yet to be determined.
AB - BACKGROUND: The output of many healthy physiological systems displays fractal fluctuations with self-similar temporal structures. Altered fractal patterns are associated with pathological conditions. There is evidence that patients with bipolar disorder have altered daily behaviors.METHODS: To test whether fractal patterns in motor activity are altered in patients with bipolar disorder, we analyzed 2-week actigraphy data collected from 106 patients with bipolar disorder type I in a euthymic state, 73 unaffected siblings of patients, and 76 controls. To examine the link between fractal patterns and symptoms, we analyzed 180-day actigraphy and mood symptom data that were simultaneously collected from 14 patients.RESULTS: Compared to controls, patients showed excessive regularity in motor activity fluctuations at small time scales (<1.5 h) as quantified by a larger scaling exponent (α1 > 1), indicating a more rigid motor control system. α1 values of siblings were between those of patients and controls. Further examinations revealed that the group differences in α1 were only significant in females. Sex also affected the group differences in fractal patterns at larger time scales (>2 h) as quantified by scaling exponent α2. Specifically, female patients and siblings had a smaller α2 compared to female controls, indicating more random activity fluctuations; while male patients had a larger α2 compared to male controls. Interestingly, a higher weekly depression score was associated with a lower α1 in the subsequent week.CONCLUSIONS: Our results show sex- and scale-dependent alterations in fractal activity regulation in patients with bipolar disorder. The mechanisms underlying the alterations are yet to be determined.
KW - Actigraphy
KW - Bipolar disorder
KW - Fractal patterns
KW - Mood disorder
KW - Scale invariance
KW - Sleep-wake rhythm
UR - http://www.scopus.com/inward/record.url?scp=85082590760&partnerID=8YFLogxK
U2 - 10.1017/S0033291720000331
DO - 10.1017/S0033291720000331
M3 - Article
C2 - 32234100
AN - SCOPUS:85082590760
SN - 0033-2917
VL - 51
SP - 1562
EP - 1569
JO - Psychological medicine
JF - Psychological medicine
IS - 9
ER -