Does a low Digit Symbol Substitution Test score predict dementia and death?
Answered November 2, 20266 sources
EvidenceBModerateGood evidence in people with one real weakness. New studies could change the answer.
Yes, in older adults a low score on this test is linked to a higher risk of death. It is also linked to dementia, though the dementia studies used related speed tests.
Who it's for
Older adults; it can't tell any one person's future.
What to expect
Lower scores go with higher group risk of death and dementia.
Watch out for
Most dementia evidence comes from similar tests, not this one.
Lower digit symbol scores go with a higher risk of death
Each dot shows the risk ratio for death with a line for its likely range, after adjustment for other risk factors.
← BetterWorse →
No difference
Lower score, men followed 5 years1.44 (1.12 to 1.86)Clear worsening
11.5
risk of death vs. higher score, 1 = same
Lower digit symbol scores go with a higher risk of death
A study that followed 3,156 well-functioning older adults for a median of 8.4 years linked lower scores to a higher risk of death and of new disability, after adjusting for age, heart disease and brain scan changes1Observational study · 2008 · 704 peopleAssociation between lower digit symbol substitution test score and slower gait and greater risk of mortality and of developing incident disability in well-functioning older adults.In well-functioning older adults, low DSST score and slow gait, alone or in combination, could be risk factors for mortality and for developing disability, independent of other risk factors, including measures of brain integrity.J Am Geriatr Soc. Death rates were 16.3 per 1,000 person-years in people with neither low scores nor slow walking, 20.8 with slow walking only, 42.8 with a low score only, and 61.2 with both1Observational study · 2008 · 704 peopleAssociation between lower digit symbol substitution test score and slower gait and greater risk of mortality and of developing incident disability in well-functioning older adults.In well-functioning older adults, low DSST score and slow gait, alone or in combination, could be risk factors for mortality and for developing disability, independent of other risk factors, including measures of brain integrity.J Am Geriatr Soc.
A study of 1,118 men followed for 5 years linked a score 10 points lower to a 44% higher relative risk How much more or less likely something is in one group than another, as a ratio. A big relative change can still be a small change for any one person. of death after adjustment4Observational study · 1995 · 130 peoplePerformance on the digit symbol substitution test and 5-year mortality in the Western Collaborative Group Study.If age-related slowing of information processing is a marker for aging of the central nervous system, then people with lower digit symbol scores may be "older" physiologically than similarly aged persons with higher digit symbol scores. Aging of the central nervous system might be expected to reduce adaptive capacity…Am J Epidemiol. Unadjusted, the relative risk was 79% higher4Observational study · 1995 · 130 peoplePerformance on the digit symbol substitution test and 5-year mortality in the Western Collaborative Group Study.If age-related slowing of information processing is a marker for aging of the central nervous system, then people with lower digit symbol scores may be "older" physiologically than similarly aged persons with higher digit symbol scores. Aging of the central nervous system might be expected to reduce adaptive capacity…Am J Epidemiol.
A study that followed 1,559 older adults in the Netherlands for up to 21 years found slow processing speed on a coding task linked to nearly twice the risk of death5Observational study · 2017 · 1,559 peopleGait Speed and Processing Speed as Clinical Markers for Geriatric Health Outcomes.Slowing of thought is as relevant as slowing of movement to predict adverse health outcomes, because they seem to represent separate underlying pathologies.Am J Geriatr Psychiatry. The same slowing was linked to lasting thinking decline, with a very large relative risk that came from few cases and a wide margin of error5Observational study · 2017 · 1,559 peopleGait Speed and Processing Speed as Clinical Markers for Geriatric Health Outcomes.Slowing of thought is as relevant as slowing of movement to predict adverse health outcomes, because they seem to represent separate underlying pathologies.Am J Geriatr Psychiatry.
In a study of 2,938 Swedish adults, people who developed dementia scored worse on processing speed at the start3Observational study · 2014 · 2,938 peopleWalking speed, processing speed, and dementia: a population-based longitudinal study.Processing speed may play an important role for the association between walking speed and dementia. The slowing of walking speed appears to occur secondary to slowing of processing speed in the path leading to dementia.J Gerontol A Biol Sci Med Sci. That study used a mix of speed tests, not this one3Observational study · 2014 · 2,938 peopleWalking speed, processing speed, and dementia: a population-based longitudinal study.Processing speed may play an important role for the association between walking speed and dementia. The slowing of walking speed appears to occur secondary to slowing of processing speed in the path leading to dementia.J Gerontol A Biol Sci Med Sci.
A study of 4,072 older adults in Japan used a tablet version of this test as one part of a thinking battery. Low scores on two or more parts were linked to about 4 times the dementia risk over 24 months6Observational study · 2018 · 4,072 peopleCognitive Frailty and Incidence of Dementia in Older Persons.Individuals with cognitive frailty had the highest risk of dementia. Future research should implement dementia prevention strategies among older persons with cognitive frailty.J Prev Alzheimers Dis. Only 81 people developed dementia, so the estimate is imprecise, and the test's own contribution can't be separated out6Observational study · 2018 · 4,072 peopleCognitive Frailty and Incidence of Dementia in Older Persons.Individuals with cognitive frailty had the highest risk of dementia. Future research should implement dementia prevention strategies among older persons with cognitive frailty.J Prev Alzheimers Dis.
These figures compare groups, so the gain or loss for one person depends on how high their risk was to begin with.
Key studies
Study
Who
What it found
Study following people, 20081Observational study · 2008 · 704 peopleAssociation between lower digit symbol substitution test score and slower gait and greater risk of mortality and of developing incident disability in well-functioning older adults.In well-functioning older adults, low DSST score and slow gait, alone or in combination, could be risk factors for mortality and for developing disability, independent of other risk factors, including measures of brain integrity.J Am Geriatr Soc
3,156 older adults, 8.4 years
Low score linked to more deaths and disability
Study following people, 19954Observational study · 1995 · 130 peoplePerformance on the digit symbol substitution test and 5-year mortality in the Western Collaborative Group Study.If age-related slowing of information processing is a marker for aging of the central nervous system, then people with lower digit symbol scores may be "older" physiologically than similarly aged persons with higher digit symbol scores. Aging of the central nervous system might be expected to reduce adaptive capacity…Am J Epidemiol
1,118 men, 5 years
10 points lower linked to 44% higher death risk
Study following people, 20175Observational study · 2017 · 1,559 peopleGait Speed and Processing Speed as Clinical Markers for Geriatric Health Outcomes.Slowing of thought is as relevant as slowing of movement to predict adverse health outcomes, because they seem to represent separate underlying pathologies.Am J Geriatr Psychiatry
1,559 older adults, up to 21 years
Slow processing linked to nearly double the death risk
Study following people, 20143Observational study · 2014 · 2,938 peopleWalking speed, processing speed, and dementia: a population-based longitudinal study.Processing speed may play an important role for the association between walking speed and dementia. The slowing of walking speed appears to occur secondary to slowing of processing speed in the path leading to dementia.J Gerontol A Biol Sci Med Sci
2,938 adults over 60
Slow processing at start in those who developed dementia
Study following people, 20186Observational study · 2018 · 4,072 peopleCognitive Frailty and Incidence of Dementia in Older Persons.Individuals with cognitive frailty had the highest risk of dementia. Future research should implement dementia prevention strategies among older persons with cognitive frailty.J Prev Alzheimers Dis
4,072 adults over 65
Low scores on 2 or more thinking tests linked to higher dementia risk
Safety
The test is a paper-and-pencil task taking 90 to 120 seconds2Review · 2018Digit Symbol Substitution Test: The Case for Sensitivity Over Specificity in Neuropsychological Testing.The DSST is sensitive to the presence of cognitive dysfunction as well as to change in cognitive function across a wide range of clinical populations but has low specificity to determine exactly which cognitive domain has been affected. However, the DSST offers a practical and effective method to monitor cognitive…J Clin Psychopharmacol. It measures thinking dysfunction but can't say which thinking skill is affected2Review · 2018Digit Symbol Substitution Test: The Case for Sensitivity Over Specificity in Neuropsychological Testing.The DSST is sensitive to the presence of cognitive dysfunction as well as to change in cognitive function across a wide range of clinical populations but has low specificity to determine exactly which cognitive domain has been affected. However, the DSST offers a practical and effective method to monitor cognitive…J Clin Psychopharmacol.
What we don't know
Whether a low score on this test alone predicts dementia, since the dementia studies used related tests or batteries.
Whether acting on a low score changes outcomes, or how well it sorts individuals.
Written by AI from the studies listed, without review by a clinician, and graded with the GRADE method. It can be wrong, so check the studies it cites. Education, not medical advice.