Evidence

The research behind each measure

Physical and cognitive change often travel together. In one study of 954 older adults, weaker pinch strength was linked to cognitive impairment even after accounting for grip strength.1

Pebl checks strength, dexterity, reaction time and memory in under five minutes. Here is what published research says about each one, with every source linked at the bottom of the page.

These studies were not done with Pebl. Pebl follows change against each person's own baseline; it does not diagnose.

01 · Strength

Grip and pinch strength

Grip strength is one of the most studied markers of aging, and it is recommended for routine use with older adults.2

What the research shows

  • In a study of nearly 140,000 adults in 17 countries, each 5 kg lower grip strength was associated with about a 16% higher risk of death over roughly four years.3
  • In UK Biobank, about 500,000 adults, lower grip strength was linked to higher risk of death from any cause, heart disease, lung disease and cancer.4
  • Men with the weakest grip in midlife had nearly three times the odds of slow walking 25 years later.5
  • Weak grip is one of the five criteria in the most widely used definition of physical frailty, led by Johns Hopkins researchers.6
  • Pinch has been compared with grip directly. In 954 adults aged 60 and over, a model using pinch strength alone identified cognitive impairment better than one using grip strength alone.1
  • Over the next two years in the same group, pinch strength predicted falls about as well as grip strength did. Pinch readings also varied more from one attempt to the next.7

How Pebl measures it

A load cell measures pinch force in kilograms. Above it, a patent-pending 64-point pressure map records where the force lands: a force print of each pinch. When a press lands off-centre, Pebl uses that map to correct the reading. Pinch is harder to measure consistently than grip, and that correction is how Pebl makes a pinch reading steady enough to stand in for grip strength.

The 64-point pressure map under the thumb, with the centre of pressure marked. 3D render; readout simulated.
An off-centre press is corrected using the centre of pressure. Illustration with tilt exaggerated; readout simulated.

02 · Dexterity

Steadiness and fine control

Holding a steady, precise pinch gets harder with age. In a lab study, adults aged 65 to 79 had 26% less maximum pinch force than young adults and were less steady holding a light pinch.8

What the research shows

  • Motion sensors (accelerometers and gyroscopes) are an established, validated way to measure the size and frequency of tremor.9
  • Across 928 patients in five labs, instrument-measured tremor size tracked clinicians' tremor ratings.10

How Pebl measures it

While the hand holds a steady pinch, a 6-axis motion sensor and a 3-axis magnetometer record nine axes of movement. Pebl combines them with the force and pressure-map signals into one steadiness index, tracked against the person's own baseline. It does not diagnose tremor or any condition.

Motion, force and contact signals combined into one steadiness index. Data simulated; a relative index, not a diagnosis.
Inside the 6-axis motion sensor: accelerometer and gyroscope. Illustration, not to scale.
The 3-axis magnetometer adds three more axes. Illustration, not to scale.

03 · Reaction

Reaction time

How quickly and how consistently someone responds says something about the whole system, not only the hand.

What the research shows

  • In 5,134 US adults followed for about 15 years, slower and more variable reaction times were associated with higher risk of death.11
  • A review of 22 long-term studies found that more variable reaction times were consistently associated with cognitive decline and death.12
  • In a one-year study of 341 women aged 65 and over, slow reaction time was associated with repeated falls.13

How Pebl measures it

Pebl's screen shows a stream of common cues and an occasional rare one. The person presses only for the rare one, and Pebl records the response time in milliseconds. Each result is compared with the person's own earlier results, not with a population cut-off.

The reaction test on Pebl's screen.

04 · Memory

Memory and thinking speed

What the research shows

  • The ACTIVE trial, co-led by Johns Hopkins researchers, randomized 2,802 adults aged 65 and over to cognitive training or none, then tracked dementia diagnoses for 20 years. Those who did speed-of-processing training with booster sessions had a 25% lower rate of dementia diagnosis than the control group. Memory and reasoning training showed no significant effect.14

How Pebl measures it

Pebl shows a short sequence on its screen and the person repeats it. Each result is compared with the person's own earlier results, not with a population cut-off. The memory task is a measure, not a training program, and it was not part of the studies above.

The sequence-memory game on Pebl's screen. 3D render.

05 · Vibration sense

Vibration sense

In development

Vibration perception threshold is a standard test of large nerve-fibre function.15 In people with diabetes, high thresholds at the foot predicted later foot ulcers.16

How Pebl measures it

We are developing a separate device for vibration-sense testing. It is not part of the current Pebl, and we make no claims for it yet.

Sources

All are observational studies or reviews except ACTIVE, a randomized trial. They show associations in the groups studied, not cause and effect, and none of them used Pebl.

  1. 1.Ren J, Chen X, Jiang W, Chen Q, Yang M. Pinch strength as an independent correlate of cognitive impairment beyond grip strength in older adults. Arch Gerontol Geriatr. 2025;137:105938. doi.org/10.1016/j.archger.2025.105938
  2. 2.Bohannon RW. Grip strength: an indispensable biomarker for older adults. Clin Interv Aging. 2019;14:1681–91. doi.org/10.2147/CIA.S194543
  3. 3.Leong DP, Teo KK, Rangarajan S, et al. Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet. 2015;386(9990):266–73. doi.org/10.1016/S0140-6736(14)62000-6
  4. 4.Celis-Morales CA, Welsh P, Lyall DM, et al. Associations of grip strength with cardiovascular, respiratory, and cancer outcomes and all cause mortality: prospective cohort study of half a million UK Biobank participants. BMJ. 2018;361:k1651. doi.org/10.1136/bmj.k1651
  5. 5.Rantanen T, Guralnik JM, Foley D, et al. Midlife hand grip strength as a predictor of old age disability. JAMA. 1999;281(6):558–60. doi.org/10.1001/jama.281.6.558
  6. 6.Fried LP, Tangen CM, Walston J, et al. Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci. 2001;56(3):M146–56. doi.org/10.1093/gerona/56.3.m146
  7. 7.Chen X, Zhu G, Jiang W, Chen Q, Yang M. Pinch strength vs handgrip strength for screening sarcopenia and predicting adverse health outcomes in older adults. J Am Med Dir Assoc. 2026;27(1):105980. doi.org/10.1016/j.jamda.2025.105980
  8. 8.Ranganathan VK, Siemionow V, Sahgal V, Yue GH. Effects of aging on hand function. J Am Geriatr Soc. 2001;49(11):1478–84. doi.org/10.1046/j.1532-5415.2001.4911240.x
  9. 9.Haubenberger D, Abbruzzese G, Bain PG, et al. Transducer-based evaluation of tremor. Mov Disord. 2016;31(9):1327–36. doi.org/10.1002/mds.26671
  10. 10.Elble RJ, Pullman SL, Matsumoto JY, et al. Tremor amplitude is logarithmically related to 4- and 5-point tremor rating scales. Brain. 2006;129(Pt 10):2660–6. doi.org/10.1093/brain/awl190
  11. 11.Hagger-Johnson G, Deary IJ, Davies CA, Weiss A, Batty GD. Reaction time and mortality from the major causes of death: the NHANES-III study. PLoS One. 2014;9(1):e82959. doi.org/10.1371/journal.pone.0082959
  12. 12.Haynes BI, Bauermeister S, Bunce D. A systematic review of longitudinal associations between reaction time intraindividual variability and age-related cognitive decline or impairment, dementia, and mortality. J Int Neuropsychol Soc. 2017;23(5):431–45. doi.org/10.1017/S1355617717000236
  13. 13.Lord SR, Ward JA, Williams P, Anstey KJ. Physiological factors associated with falls in older community-dwelling women. J Am Geriatr Soc. 1994;42(10):1110–7. doi.org/10.1111/j.1532-5415.1994.tb06218.x
  14. 14.Coe NB, Miller KEM, Sun C, et al. Impact of cognitive training on claims-based diagnosed dementia over 20 years: evidence from the ACTIVE study. Alzheimers Dement (N Y). 2026;12(1):e70197. doi.org/10.1002/trc2.70197 A 2026 reanalysis argues these results do not hold after correcting for multiple comparisons (Dickens WT, Alzheimers Dement (N Y) 2026;12(2):e70280). doi.org/10.1002/trc2.70280
  15. 15.Martin CL, Waberski BH, Pop-Busui R, et al. Vibration perception threshold as a measure of distal symmetrical peripheral neuropathy in type 1 diabetes: results from the DCCT/EDIC study. Diabetes Care. 2010;33(12):2635–41. doi.org/10.2337/dc10-0616
  16. 16.Young MJ, Breddy JL, Veves A, Boulton AJ. The prediction of diabetic neuropathic foot ulceration using vibration perception thresholds: a prospective study. Diabetes Care. 1994;17(6):557–60. doi.org/10.2337/diacare.17.6.557

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