Brain Age Gap

Report raw predicted-minus-chronological brain-age gaps and invert a caller-supplied training calibration predicted=a+b·age; not a disease or biological-age diagnosis.

Description

A brain-age gap compares a model-predicted age with chronological age.

A brain-age gap compares a model-predicted age with chronological age. Calibration can correct a supplied linear prediction bias before subtraction.

The tool returns rawGapsYears (raw gaps years); calibratedGapsYears (calibrated gaps years). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.

When to use Brain Age Gap

Use Brain Age Gap when you already have predictedAgesYears, chronologicalAgesYears, calibrationInterceptYears, calibrationSlope and want rawGapsYears, calibratedGapsYears. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.

How to use Brain Age Gap and understand its results

Enter predictedAgesYears, chronologicalAgesYears, calibrationInterceptYears, calibrationSlope using the field table below. Match the units, ordering and data boundaries described in the calculation.
Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
Read rawGapsYears, calibratedGapsYears. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.

Input field	Meaning	Value type and bounds	Requirement
predictedAgesYears	Predicted ages years	list of number	Required
chronologicalAgesYears	Chronological ages years	list of number	Required
calibrationInterceptYears	Calibration intercept years	number	Required
calibrationSlope	Calibration slope	number	Required

Use aligned nonnegative ages, a finite intercept and positive calibration slope. Return both differences in years.

raw gap = predicted−age; calibrated gap = (predicted−intercept)/slope−age

The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.

json

{
  "input": {
    "predictedAgesYears": [
      50,
      60
    ],
    "chronologicalAgesYears": [
      40,
      60
    ],
    "calibrationInterceptYears": 10,
    "calibrationSlope": 0.8
  },
  "output": {
    "rawGapsYears": [
      10,
      0
    ],
    "calibratedGapsYears": [
      10,
      2.5
    ]
  }
}

Limitations and assumptions

The calibration must be learned on appropriate independent data. No age model or calibration is fitted and no diagnostic inference is made.

Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.

Alternative or Complementary methods

Blood Brain Barrier LogBB: Evaluate a supplied linear descriptor log10(brain/plasma) model; coefficients must be calibrated externally and predictions are not BBB transport or clinical efficacy claims. Cognitive Decline Slope: Fit longitudinal cognitive score change after caller-supplied visit-specific practice offsets; score direction and diagnostic interpretation are not assumed.

Methodological background: Least squares estimation.^[1]

References

Least squares estimation — NIST/SEMATECH

Similar or alternative tools

Blood Brain Barrier LogBB
Evaluate a supplied linear descriptor log10(brain/plasma) model; coefficients must be calibrated externally and predictions are not BBB transport or clinical efficacy claims.
Cognitive Decline Slope
Fit longitudinal cognitive score change after caller-supplied visit-specific practice offsets; score direction and diagnostic interpretation are not assumed.