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Cognitive tests administered through a smartphone mobile application (app) accurately and reliably detected frontotemporal lobar degeneration (FTLD), also known as frontotemporal dementia (FTD), an observational study showed.

The smartphone tests had moderate to excellent internal consistency and test-retest reliability (intraclass correlation coefficient range of 0.77-0.95), according to Adam Staffaroni, PhD, of the University of California San Francisco (UCSF), and co-authors.

Validity was supported by strong associations of smartphone test data with disease severity, brain volume, and neuropsychological measures, the researchers reported in . Smartphone measures also were more sensitive to early stages of familial FTD.

FTD is a heterogeneous group of dementias with progressive atrophy involving the frontal or temporal lobes, or both. The average age of onset is when people are in their mid-50s or 60s. About 15% to 30% of cases have a genetic cause.

The disorder has been in the spotlight after the family of actor Bruce Willis announced his diagnosis in 2023. New artistic skills also have been reported in some patients with FTD, particularly those with primary progressive aphasia variants.

FTD can be difficult to diagnose, which has hampered clinical trial recruiting, Staffaroni and colleagues noted.

"Most FTD patients are diagnosed relatively late in the disease, because they are young, and their symptoms are mistaken for psychiatric disorders," said co-author Adam Boxer, MD, PhD, also of UCSF, in a statement. "We've heard from families that they often suspect their loved one has FTD long before a physician agrees that is the diagnosis."

The study was conducted from January 2019 through July 2023 with 360 participants, who were grouped into a discovery cohort (258 people) and a validation cohort (102 people). Mean age was 54.0 and 58.1% were women.

Of 329 participants with data available on disease stage, 195 people were asymptomatic or had preclinical FTD, 66 had prodromal FTD, and 68 had symptomatic FTD.

Participants were enrolled through 18 centers of a North American FTLD research consortium () and were asked to complete testing remotely using their own phones. They performed executive functioning tasks and an associative memory task three times over 2 weeks using the mobile app.

Cognitive tasks were self-administered without supervision in a predefined order. Study partners of participants with symptomatic FTD remained nearby to help navigate the app, but were asked not to assist with testing. Tests included an adaptive associative memory task and gamified versions of classic executive functioning paradigms.

The smartphone tests were associated with disease severity (r range, 0.38-0.59), criterion-standard neuropsychological tests (r range, 0.40-0.66), and brain volume (standardized β range, 0.34-0.50).

The tests also accurately differentiated participants with dementia from controls with area under the curve (AUC) of 0.93 (95% CI 0.90-0.96), and were more sensitive to early symptoms (AUC 0.82) than the Montreal Cognitive Assessment (AUC 0.68; z of comparison, −2.49, P=0.01).

In both the discovery and validation cohorts, reliability and validity findings were similar. People with preclinical FTD who carried pathogenic variants performed significantly worse than noncarrier family controls on three app tasks, but not a composite of traditional neuropsychological measures.

This study has limitations, the researchers acknowledged. Validation analyses focused on initial task exposure, and future studies will examine whether repeated measurements improve reliability and sensitivity. Participants largely were white and college educated, and results may not apply to other groups.

The researchers collaborated with a software company which developed a smartphone platform to test memory and executive functions and assess voice recordings and body movements. They do not have plans to make the mobile app available to the public, but see its potential in clinical trials.

"Eventually, the app may be used to monitor treatment effects, replacing many or most in-person visits to clinical trials' sites," Staffaroni said.

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