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Timing of onset of cognitive decline: results from Whitehall II prospective cohort study
Open accessAbstract
OBJECTIVES: To estimate 10 year decline in cognitive function from longitudinal data in a middle aged cohort and to examine whether age cohorts can be compared with cross sectional data to infer the effect of age on cognitive decline. DESIGN: Prospective cohort study. At study inception in 1985-8, there were 10,308 participants, representing a recruitment rate of 73%. SETTING: Civil service departments in London, United Kingdom. PARTICIPANTS: 5198 men and 2192 women, aged 45-70 at the beginning of cognitive testing in 1997-9. MAIN OUTCOME MEASURE: Tests of memory, reasoning, vocabulary, and phonemic and semantic fluency, assessed three times over 10 years. RESULTS: All cognitive scores, except vocabulary, declined in all five age categories (age 45-49, 50-54, 55-59, 60-64, and 65-70 at baseline), with evidence of faster decline in older people. In men, the 10 year decline, shown as change/range of test × 100, in reasoning was -3.6% (95% confidence interval -4.1% to -3.0%) in those aged 45-49 at baseline and -9.6% (-10.6% to -8.6%) in those aged 65-70. In women, the corresponding decline was -3.6% (-4.6% to -2.7%) and -7.4% (-9.1% to -5.7%). Comparisons of longitudinal and cross sectional effects of age suggest that the latter overestimate decline in women because of cohort differences in education. For example, in women aged 45-49 the longitudinal analysis showed reasoning to have declined by -3.6% (-4.5% to -2.8%) but the cross sectional effects suggested a decline of -11.4% (-14.0% to -8.9%). CONCLUSIONS: Cognitive decline is already evident in middle age (age 45-49).
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Written from the paper’s full text.
TL;DR
In the Whitehall II prospective cohort, cognitive scores except vocabulary declined over 10 years in all age groups from 45–49 to 65–70, with faster decline at older ages. Cross-sectional age comparisons overestimated cognitive decline in women, probably because of cohort differences in education.
Key findings
- All cognitive scores except vocabulary declined in all five baseline age categories (45–49, 50–54, 55–59, 60–64, 65–70), with evidence of faster decline in older people. In men, 10-year decline in reasoning was −3.6% (95% CI −4.1% to −3.0%) in those aged 45–49 and −9.6% (−10.6% to −8.6%) in those aged 65–70; in women, the corresponding declines were −3.6% (−4.6% to −2.7%) and −7.4% (−9.1% to −5.7%).
- Longitudinal and cross-sectional estimates diverged, especially in women: in women aged 45–49, reasoning declined by −3.6% (−4.5% to −2.8%) longitudinally, but cross-sectional effects suggested a decline of −11.4% (−14.0% to −8.9%).
- Adjustment for education did not change longitudinal estimates much but substantially reduced cross-sectional estimates of ageing, consistent with cohort differences in education. For women aged 45–49 at baseline, 34% had less than secondary school education, 28% secondary school, and 40% a university degree; for women aged 55–59, the corresponding figures were 58%, 25%, and 17%.
- Vocabulary was little influenced by age; significant declines were seen for all tests except vocabulary in all age categories in both men and women.
Methods
- Prospective cohort study using Whitehall II data; cognitive testing was introduced at phase 5 (1997–9) and repeated at phases 7 (2002–4) and 9 (2007–9). Analysis included 7390 participants (5198 men, 2192 women) aged 45–70 at baseline; 4675 (63%) had complete data at all three phases.
- Cognitive battery included the Alice Heim 4-I reasoning test, a 20-word free recall memory test, phonemic and semantic fluency tests, and the Mill Hill vocabulary test. Results were expressed as percent change (change/range of test × 100).
- Linear mixed models with random intercept and slope estimated 10-year decline, including age cohort × time interaction terms and stratification by sex; cross-sectional linear regression at baseline was compared with longitudinal estimates. Analyses used SAS Proc Mixed version 9.1.
Limitations
- The paper states that longitudinal data can underestimate age effects because of practice effects and selective sample retention; non-response was higher in older individuals, though the overall response rate was 80% (7390/9250) among those invited to cognitive testing.
- The paper states that Whitehall II is not representative of the general population: participants were mostly white collar workers in relatively stable employment and two thirds were men, so results could underestimate cognitive decline at the population level.
- The paper notes that adjustment for education may not capture all cohort-related effects and may overcorrect by attributing shared variance between age and education to education. Evident from the text: cognitive testing began at age 45, so the study cannot determine whether decline begins before age 45.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There was a cross sectional association between age at baseline, categorised into five age cohorts of five years each spanning 45-70 years, and all cognitive scores (all P<0.001), except vocabulary in men (P=0.13)”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passes- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“and -9.6% (-10.6% to -8.6%) in those aged 65-70.”
- Also stated in: § Results · plain
“while in those aged 65-70 it was -9.6% (-10.6% to -8.6%)”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Results · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“and -7.4% (-9.1% to -5.7%).”
- Also stated in: § Results · plain
“and -7.4% (-9.1% to -5.7%) in those aged 65-70.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Results · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In women, the corresponding decline was -3.6% (-4.6% to -2.7%)”
- Also stated in: § Results · plain
“In women, the corresponding decline was -3.6% (-4.6% to -2.7%) in those aged 45-49”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Results · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There were considerable cohort differences in education in women.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“with evidence of faster decline in older people.”
- Also stated in: § Results · hedged
“There was some evidence of greater decline at older ages and of a linear trend in decline with increasing age for some of the tests, particularly in men”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Results · hedged
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“suggest that in women, but not men, the cross sectional analysis considerably overestimated the effect of ageing.”
- Also stated in: § Discussion · plain
“cross sectional data considerably overestimated cognitive decline among women but not in men”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Discussion · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In men, the 10 year decline, shown as change/range of test×100, in reasoning was -3.6% (95% confidence interval -4.1% to -3.0%) in those aged 45-49 at baseline”
- Also stated in: § Results · plain
“in men aged 45-49 at baseline, 10 year decline in reasoning was -3.6% (95% confidence interval -4.1% to -3.0%)”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Results · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The results for all tests, except vocabulary, showed significant declines in all age categories in both men and women as the confidence intervals did not include zero.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Our data show larger cohort effects in women because of differences in educational attainment across the birth cohorts in our study population.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- It may state two separate claims as one. 12
- Probably not a substantial claim. 15
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“the longitudinal analysis in women shows reasoning to have declined by -3.6% (-4.5% to -2.8%) in those aged 45-49 but the cross sectional effects suggest a decline of -11.4% (-14.0% to -8.9%).”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“All cognitive scores, except vocabulary, declined in all five age categories (age 45-49, 50-54, 55-59, 60-64, and 65-70 at baseline)”
- Also stated in: § Discussion · plain
“average performance in all cognitive domains, except vocabulary, declined over follow-up in all age groups, even in those aged 45-49.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
- Also stated in: § Discussion · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Adjustment for education did not change the longitudinal estimates much but substantially reduced the cross sectional estimates of the effect of ageing on cognitive decline.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Rests on an assumption: Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
- Rests on an assumption: The cognitive tests are valid measures of cognitive function in this middle-aged population.
- Rests on an assumption: Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
In the paper
“Clinicopathological studies show good correlation between neuropathology and the severity of cognitive decline, [9][10][11]”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Introduction
What the sources say
- Not checked yetcites [9][10][11]
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“There is a finely graded inverse association between age and cognitive performance, [3][4][5]”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Introduction
What the sources say
- Not checked yetcites [3][4][5]
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“Emerging consensus on the long gestation period of dementia 14 15 also suggests that adults aged under 60 are likely to experience age related cognitive decline.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Introduction
What the sources say
- Not checked yetcites 14 15
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“As non-response was not substantial (the overall response rate was 80% (7390/9250) in those invited to cognitive testing), however, major bias is unlikely.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Strength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Longitudinal data are known to underestimate the effect of age because of practice effects 22 and are subject to selective sample retention.23”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
What the sources say
- Not checked yetcites [22]
- Not checked yetcites [23]
Strength:boosted· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Cross sectional data might not accurately distinguish longitudinal change-that is, the effect of chronological age-from secular change, also called “cohort” effects.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Introduction
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“The mini-mental state examination, 17 although included in the test battery, was not used in the current analysis because of ceiling effects (that is, simple tests leading to little variability in scores).”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Cognitive function
What the sources say
- Not checked yetcites [17]
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“The sex specific cohort differences in educational attainment seen in this sample, however, reflect global trends in educational opportunities across the 20th century.24 25”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
What the sources say
- Not checked yetcites 24 25
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“In our study non-response was higher in the older individuals, affecting both cross sectional as well and longitudinal estimates.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The participants are mostly white collar workers in relatively stable employment and two thirds are men, implying that our results could underestimate cognitive decline at the population level.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“There is emerging consensus that “what is good for our hearts is also good for our heads,” 36 37”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Implications and conclusions
What the sources say
- Not checked yetcites 36 37
Strength:hedged· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✗ Checkable: fails✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Our analysis was based on 7390 (5198 men and 2192 women) of the 9250 individuals still in the study.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Strength:plain· not yet calibratedn = 7,390Tests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The exposure, in this case time over 10 years, is uniformly applicable to all age cohorts in the analysis.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The obvious advantage of using longitudinal analysis is that the estimates of cognitive decline are based on changes within an individual, and these are unlikely to be affected by error arising from natural variation between individuals.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“One challenge in small scale studies set up to investigate “cognitive ageing” is that they might be based on a selected sample of individuals.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Strength:hedged· not yet calibratedTests✓ Asserted: passes✗ Checkable: fails✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Of the 10 308 participants at study inception (1985-8), 306 had died and 752 had withdrawn from the study before the start of the cognitive data collection in 1997-9.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Strength:plain· not yet calibratedn = 10,308Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Those included in the analyses were more educated (29.5% v 20.8% had a university degree, P<0.001) and were younger”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Tests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“The results for vocabulary were expected as it is known to be little influenced by age. 4”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
What the sources say
- Not checked yetcites [4]
Strength:boosted· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“These estimates, however, reflect both the effects of chronological ageing and cohort effects, each produced by distinct underlying mechanisms.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Of the 7390 individuals included in the analysis, we had complete data for 4675 (63%) at all three phases, 1613 at two phases, and 1102 at only one phase.”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Results
Strength:plain· not yet calibratedn = 7,390Tests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“Cohort effects are produced when a birth cohort enters adult life with long lasting effects on cognitive function because of childhood experiences like quality of education, nutrition, socioeconomic circumstances, etc. [31][32][33]”
§ Timing of onset of cognitive decline: results from Whitehall II prospective cohort study > Discussion
What the sources say
- Not checked yetcites [31][32][33]
Tests✓ Asserted: passes✗ Checkable: fails✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence.
The paper relies on this without support.
Missing cognitive data are missing at random, so linear mixed models yield unbiased estimates.
“Linear mixed models 21 were used to estimate cognitive decline over follow-up.This method uses all available data over follow-up, takes into account the fact that repeated measures on the same individual are correlated with each other, and can handle missing data.”
The paper relies on this without support.
The cognitive tests are valid measures of cognitive function in this middle-aged population.
“The cognitive test battery, administered at three clinical examinations over 10 years (phases 5, 7, and 9), was chosen to provide a comprehensive assessment of cognitive function and be appropriate for this population composed of individuals younger than in most studies on cognitive ageing.”
The paper relies on this without support.
Cognitive decline over the 10-year follow-up is linear in time within each age cohort.
“The models included terms for time (age in years, divided by 10 so the coefficients yield effects of decline over 10 years), age cohorts (age at baseline in five year bands) to adjust for secular effects, and an interaction term between age cohort and time, separately in men and women.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The cited source says what the claim attributes to it.
In the citing paper
“The decreased cognitive performance begins around midlife from 45 years [173] and increases with age due to structural and functional changes in the brain (for instance, regional brain volumes and integrity of the white matter, reduction in the fluidity of brain membranes, and changes in lipid composition) [163,174,175,176].”
From Alzheimer's Disease: Treatment Strategies and Their Limitations. (2022) · cites this paper as [173]
In the citing paper
“For instance, in comparison with longitudinal design, cross-sectional analysis was found to overestimate age-associated cognitive decline (Singh-Manoux et al, 2012).”
From Microglia Priming with Aging and Stress (2017) · cites this paper as Singh-Manoux et al, 2012
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Two values given for reasoning decline in younger men
MinorThe results report a 10-year reasoning decline of -3.6% for men aged 45-49 at baseline, but the concluding summary reports -3.5% for the same group.
“For example, in men aged 45-49 at baseline, 10 year decline in reasoning was -3.6% (95% confidence interval -4.1% to -3.0%)”
“The 10 year decline in reasoning was -3.5% in men aged 45-49 at baseline and -9.6% among those aged 65-70”
Conflicting secondary-school education percentage for younger women
MinorThe results state that 28% of women aged 45-49 had completed secondary school, while the table footnote gives 26% for the same group. The results' three education percentages for these women also total 102%.
“For women the corresponding figures were 34%, 28%, and 40%.”
“In those aged 45-49 at baseline 30% of men and 34% of women had less than secondary school education, 28% and 26% had secondary school education, and 42% and 40% had a university degree.”
Citations
Cites
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Hirono, N., Mori, E., Ikejiri, Y., Imamura, T., Shimomura, T., Hashimoto, M., Yamashita, H., & Ikeda, M. (1997) · PubMed · Cited by 21,012
Kok, J. S., Berg, I. J., & Scherder, E. J. A. (2013) · Dementia and Geriatric Cognitive Disorders Extra · doi:10.1159/000353441 · Cited by 20,589
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“The decreased cognitive performance begins around midlife from 45 years [173] and increases with age due to structural and functional changes in the brain (for instance, regional brain volumes and integrity of the white matter, reduction in the fluidity of brain membranes, and changes in lipid composition) [163,174–17…”
Background
Metadata
- Authors
- Singh-Manoux, A., Kivimaki, M., Glymour, M. M., Elbaz, A., Berr, C., Ebmeier, K. P., Ferrie, J. E., & Dugravot, A.
- Affiliations
- Harvard University (US)
- Inserm (FR)
- Warneford Hospital (GB)
- University of Bristol (GB)
- Venue
- BMJ
- Publisher
- BMJ
- Published
- 2012-01-05
- Volume
- 344
- Issue
- jan04 4
- Pages
- d7622-d7622
- ISSN
- 0007-1447 (ISSN-L)
- 0959-8138
- 1468-5833
- PMC
- PMC3281313
- OpenAlex
- W2168922851
- Cited by
- 836
- References
- 41
- Citations by year
- 2026: 45 · 2025: 39 · 2024: 66 · 2023: 67 · 2022: 52 · 2021: 81 · 2020: 70 · 2019: 64 · 2018: 44 · 2017: 54 · 2016: 51 · 2015: 45 · 2014: 52 · 2013: 55 · 2012: 46
- FWCI
- 44.75
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- cc-by-nc
- Locations
- BMJ (publishedVersion, cc-by-nc)
- Europe PMC (PubMed Central) (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
- HAL (submittedVersion, other-oa)
- UCL Discovery (University College London) (submittedVersion)
- Funders
- British Heart Foundation (R01 AG013196, R01AG034454, RG/07/008/23674)
- Bupa Foundation
- European Science Foundation
- Academy of Finland (R01 AG034454)
- National Institutes of Health
- Medical Research Council (R01AG034454, G0902037)
- National Institute on Aging (R01AG034454, R01AG013196)
- National Heart, Lung, and Blood Institute (R01HL036310)
- Topics
- Health Sciences › Medicine › Psychiatry and Mental health › Dementia and Cognitive Impairment Research
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Cognitive Abilities and Testing
- Social Sciences › Psychology › Developmental and Educational Psychology › Aging and Gerontology Research
- Keywords
- cognitive decline, cognitive aging, middle age (human life stage), age cohort effects, sex differences, reasoning, memory, vocabulary, fluency, Whitehall II cohort, public sector employees
- MeSH terms
- Adult, Aged, Aging, Cognition Disorders, Educational Status, Epidemiologic Methods, Female, Humans, London, Male, Middle Aged, Neuropsychological Tests, Age of Onset
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-10, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-10 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
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