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Related Concept Videos

Bode Plots Construction01:24

Bode Plots Construction

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The Bode plot is an essential tool in control system analysis, mapping the frequency response of a system through a magnitude plot and a phase plot, both against a logarithmic frequency axis. To construct a Bode plot, consider the transfer function H(ω):
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RLC Series Circuits: Impedance01:29

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When current flow is opposed in a DC or AC circuit, it is referred to as resistance or impedance, respectively. Impedance plays a key role in determining the performance of AC circuits. It is represented by Z, which is a combination of resistance and reactance, and depends upon the angular frequency, measured in ohms.
Thus, the magnitude of the impedance is given by the following equation,
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Phasor Relationships for Circuit Elements01:16

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Phasor representation is a powerful tool used to transform the voltage-current relationship for resistors, inductors, and capacitors from the time domain to the frequency domain. This transformation simplifies the analysis of alternating current (AC) circuits.
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Impedances and Admittance01:23

Impedances and Admittance

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In the realm of AC circuits, passive circuit elements like resistors, inductors, and capacitors take on a different character when characterized by phasor voltage and current. Their behavior is expressed through impedance, a vital concept in AC circuit analysis.
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Gain01:15

Gain

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Gain and phase shift are properties of linear circuits that describe the effect a circuit has on a sinusoidal input voltage or current. The circuit's behavior that contains reactive elements will depend on the frequency of the input sinusoid. As a result, it is observed that the gain and phase shift will all be frequency functions.
Gain:
Suppose Vin is the input and Vout is the output signal to a circuit.
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Frequency Response of a Circuit01:20

Frequency Response of a Circuit

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Inductive circuits present intriguing challenges in electrical engineering, particularly during the transition from the time domain to the frequency domain. This transformation involves converting inductors into impedances and utilizing phasor representation.
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Updated: Jul 9, 2025

Author Spotlight: Unveiling Prognostic Indicators in Heart Failure - The Role of Phase Angle and Bioelectrical Impedance Analysis
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Relationship between cognitive function and phase angle measured with a bioelectrical impedance system.

Yosuke Yamada1, Kazuhisa Watanabe1, Chisato Fujisawa1

  • 1Departments of Community Healthcare and Geriatrics, Graduate School of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya City, Aichi, 466-8550, Japan.

European Geriatric Medicine
|November 28, 2023
PubMed
Summary
This summary is machine-generated.

Lower muscle quality, indicated by phase angle (PhA), is linked to worsening cognitive function in men with Alzheimer's dementia (AD) or mild cognitive impairment (aMCI). AD patients showed significantly lower PhA than those with aMCI.

Keywords:
Cognitive functionMuscle qualityPhase anglePhysical function

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Area of Science:

  • Neurology
  • Geriatrics
  • Biomarkers

Background:

  • Cognitive decline is a growing concern in aging populations.
  • Muscle quality, assessed by phase angle (PhA), is an emerging biomarker.
  • The relationship between PhA and cognitive function in dementia is not fully understood.

Purpose of the Study:

  • To investigate the association between cognitive function and PhA in patients with Alzheimer's dementia (AD) and amnesic mild cognitive impairment (aMCI).
  • To determine if PhA can differentiate between AD and aMCI.
  • To explore gender-specific differences in this relationship.

Main Methods:

  • Cross-sectional study of 153 outpatients (memory clinic, Nagoya University Hospital, 2016-2022).
  • Inclusion criteria: Mini-Mental State Examination score 20-30, diagnosis of AD or aMCI.
  • Analysis included linear regression (PhA as outcome) and logistic regression (AD diagnosis).

Main Results:

  • Phase angle (PhA) was significantly lower in the Alzheimer's dementia (AD) group compared to the amnesic mild cognitive impairment (aMCI) group.
  • Linear regression revealed that PhA decreased with higher ADAS scores, indicating poorer cognitive function.
  • Logistic regression showed that a higher PhA was associated with the absence of AD, but this association was only significant in men.

Conclusions:

  • Reduced muscle quality, reflected by lower PhA, is associated with cognitive decline in patients with AD and aMCI.
  • AD is characterized by significantly lower PhA compared to aMCI.
  • These findings support the link between poor muscle quality and impaired cognitive function, particularly in men.