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Smooth Curves, Similar Conclusions? Comparing Linear Regression and GAMLSS Neuropsychological Norms
Kirsebom, B.-E.; Myrvoll Lorentzen, I.; Espenes, J.; Vollo Eliassen, I.; Gonzalez-Ortiz, F.; Wallin, A.; Waterloo, K.; Eckerstrom et al.. medRxiv (preprint), 2026-09-04
Topic: Risk, prevention and care in population studies
ObjectiveRegression-based normative approaches are widely used in neuropsychology but often rely on score transformations to satisfy model assumptions. We compared previously published linear regression (LR)-based norms with norms derived using Generalized Additive Models for Location, Scale and Shape (GAMLSS) for the brief cognitive battery used in the Norwegian Dementia Disease Initiation (DDI) cohort. MethodGAMLSS norms were developed using the same normative samples as the original LR norms for the Consortium to Establish a Registry for Alzheimers Disease (CERAD) word list test, Trail Making Test (TMT) A and B, FAS phonemic fluency, and Visual Object and Space Perception Battery (VOSP) Silhouettes. Expected low-score frequencies and empirical base rates were assessed in a normative subsample (n = 131). Clinical implications were evaluated in the DDI clinical cohort (n = 643) using Mild Cognitive Impairment (MCI) classification, two-year diagnostic stability and change, and cerebrospinal fluid (CSF) biomarkers. ResultsCompared with LR norms, GAMLSS yielded lower frequencies of low scores, primarily driven by CERAD delayed recall. Nevertheless, concordance between approaches was high ({kappa} = 0.91), with only 4.2% discordant classifications. Two-year diagnostic stability and change were broadly similar across approaches, and CSF biomarker profiles did not clearly favor either normative method. ConclusionsGAMLSS provided a more faithful representation of neuropsychological score distributions, particularly for bounded and non-normal outcomes. However, downstream clinical differences were modest in this setting, suggesting that well-calibrated LR norms may remain robust for clinical classification.
Key findings
- However, downstream clinical differences were modest in this setting, suggesting that well-calibrated LR norms may remain robust for clinical classification.
Why it matters
This study compared two methods for developing cognitive test norms and found high agreement between them, with only modest downstream differences in clinical classification. It is about neuropsychological testing methods and does not test any treatment, cure or prevention.
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Study details
- Participants131
- Effect size4.2%
- Evidence strengthModerate
How this study scored 16/100
Preprint — not yet peer-reviewed. It scored 32 on the same rubric, but non-peer-reviewed sources are capped at 16, so it shows as 16. Scored zero for study design and randomised / blinded because the record does not state it. We have no data on impact for its field and year, so that was left out: it earned 30 of the 94 points we could judge it on, which is 32 out of 100.
| Component | Points | Why |
|---|---|---|
| Journal tier | 2 / 10 | Tier 4 — not a peer-reviewed journal (medRxiv (preprint)) |
| Journal's citation record | 0 / 4 | Not a journal article, so the journal's record does not count |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 3 / 5 | Rated “moderate” in our summary |
| Peer-review validation | 4 / 10 | Preprint — not yet peer-reviewed. Hosted on a preprint server. |
| How recent | 5 / 5 | 2026 — within 1 year(s) of the newest study here |
| Sample size | 2 / 4 | 131 participants |
| Effect reported | 2 / 3 | Effect reported as a number, without an interval or test |
| Studied in people | 3 / 3 | Studied in people (participant count stated) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 0 / 7 | Cited 0 times (OpenAlex, 2026-10-10) |
| Citations per year | 0 / 5 | 0.0 citations a year over 2 year(s) since 2026 |
| Impact for its field and year | — / 6 | No field-weighted citation impact (OpenAlex has none yet) — left out of this score |
| Cited by studies here | 0 / 6 | No other study in this library cites it |
| Still being cited | 0 / 4 | Cited 0 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Tormod Fladby: h-index 51 (OpenAlex, whole career) |
| Institution's track record | 1 / 3 | University of Oslo: institution h-index 1,024 (OpenAlex) |
| Multi-centre collaboration | 2 / 3 | OpenAlex lists 9 institution(s) in 2 countries |
| Indexed in PubMed | 1 / 2 | Not in PubMed, but has a DOI |
| Free to read | 2 / 2 | Free to read |
| Points | 30 / 94 | Scored on 19 of 20 parts. We have no data for the rest, so they are left out: 30 of the 94 points we could judge it on is 32 out of 100. |
| Total | 32 / 100 | Capped to 16 because this is not a peer-reviewed article. |
What each of these 20 components measures, and what this score is not →
Read the original
Full text: free to read — OpenAlex lists this copy as free to read: the link above (checked 6 Feb 1020).
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. The record's author list ends in “et al.”, so not every author is named. Check the citation against the original before you use it.
APA 7th
Kirsebom, B.-E., Myrvoll Lorentzen, I., Espenes, J., Vollo Eliassen, I., Gonzalez-Ortiz, F., Wallin, A., et al. (2026). Smooth Curves, Similar Conclusions? Comparing Linear Regression and GAMLSS Neuropsychological Norms. medRxiv (preprint). https://doi.org/10.64898/2026.09.01.26361590
Vancouver
Kirsebom B.-E, Myrvoll Lorentzen I, Espenes J, Vollo Eliassen I, Gonzalez-Ortiz F, Wallin A, et al. Smooth Curves, Similar Conclusions? Comparing Linear Regression and GAMLSS Neuropsychological Norms. medRxiv (preprint). 2026. doi:10.64898/2026.09.01.26361590.
BibTeX
@article{kirsebom2026-c2d3d6b2,
author = {Kirsebom, B.-E. and Myrvoll Lorentzen, I. and Espenes, J. and Vollo Eliassen, I. and Gonzalez-Ortiz, F. and Wallin, A. and Waterloo, K. and Eckerstrom and others},
title = {{Smooth Curves, Similar Conclusions? Comparing Linear Regression and GAMLSS Neuropsychological Norms}},
journal = {medRxiv (preprint)},
year = {2026},
doi = {10.64898/2026.09.01.26361590},
url = {https://doi.org/10.64898/2026.09.01.26361590}
}
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