Table 1.

Longitudinal studies examining the association between hand cognitive perfomance

Reference (first author and year of publication)	Dataset, country	$n$	Mean age $\pm$ SD	Duration (years)	Cognitive function tests	Hand strength	Hand dexterity	Main outcome: Association
de Paula [18] (2016)	Clinic, Brazil	HE: 20, aMCI: 34, MDaMCI: 32, AD: 38	74.2	4.0	*DRS Brazil version	Not carried out	9PT	1. Significant group differences in hand dexterity were found between Healthy and MDaMC ($p=$ 0.009), HE and AD ( 0.001), and aMCI and AD ($p=$ 0.004). Hand dexterity dropped significantly in the AD group compared to the HE group, but there was no difference between HE and aMCI.2. Hand dexterity is in the order of HE $>$ aMCI $>$ MDaMCI $>$ AD.
Darweesh [29] (2017)	Population-based Rotterdam study, Netherland	4,856	70.2 $\pm$ 13.9	9.2	*MMSE,*CAMDEX*NINCDS-ADRDA*NINDS-AIREN	Not carried out	PPT	1. Using PPT for 4,856 normal people from 2000 to 2004, follow-up of patients with dementia and Parkinson’s disease until January 1, 2012.2. Diagnosed 227 dementia and 50 Parkinson’s disease over 9.2 years.3. The lower the PPT score, the higher the risk of developing dementia and Parkinson’s disease.4. Dexterity test can identify people at high risk for neurodegenerative diseases.5. 155 of 277 (56%) AD, 72 (26%) primary dementia diagnosis, 33 (12%) PD, 17 (6%) other cause PD.6. The lower the PPT score, the higher the risk of dementia and Parkinson’s disease, and the risk of degenerative diseases increased by 28% when the average PPT score decreased.7. The correlation between PPT score and degenerative disease was high in people under 70 years of age. Although there was no statistical significance, this phenomenon was evident in women.8. In the case of dementia, classification (continuous net reclassification index [NRI]) increased significantly in those aged 70 years or older, and discrimination (integrated discrimination improvement [IDI]) increased significantly in those aged 70 years or younger.9. Dexterity is strongly associated with the risk of both dementia and Parkinsonism.
Liou [17] (2020)	Taiwan Data Bank of Persons with Disability, Taiwan	mild AD: 11,935, moderate to severe AD: 20,883	mild AD: 77.9 $\pm$ 5.9, moderate to severe AD: 79.8 $\pm$ 6.5	7.0	*FUNDES-adult*WHODAS 2.0	Not carried out	*Pen-holding*Buttoning*Knotting	1. Moderate to severe AD has more difficulty in three performance skills than mild AD.2. Decreased fine motor skills of the hand have a significant risk of severe dementia.
Beeri [16] (2021)	Communities across metropolitan, USA	African American: 580, European American: 580, without dementia	73.2 $\pm$ 6.0	7.3	*NINCDS-ADRDA*CFT	Jamar dynamometer	*PPT*Electronic tapper	1. Each increase in global motor function score of 1 SD reduces the risk of AD by $\sim$20%, regardless of age, gender, education, or race.2. Motor dexterity, hand strength, and gait speed (but not leg strength) were significantly associated with incident AD and incident MCI when each of the four motor abilities was analyzed individually.3. Hand strength was the only motor component independently associated with incident AD dementia after adjusting for the other motor abilities.

9PT, nine-hole pegboard test; AD, Alzheimer’s dementia; aMCI, single-domain amnestic MCI; CAMDEX, Cambridge examination for mental disorders of the elderly; CDR, clinical dementia rating; CFT, cognitive function test; DRS, dementia rating scale; FUNDES-Adult, functioning disability evaluation scale-adult version; GDS, global deterioration scale; GPT, grooved pegboard test; HE, healthy elderly; MCI, mild cognitive impairment; MDaMCI, multiple-domain amnestic MCI; MMSE, mini-mental state examination; MoCA, Montreal cognitive assessment; NINCDS-ADRDA, National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association; NINDS-AIREN, National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l’Enseignement en Neurosciences; PPT, Purdue pegboard test; WHODAS, world health organization disability assessment schedule 2.0.