Cognitive ability in childhood and cognitive decline in mid-life: longitudinal birth cohort study
BMJ 2004; 328 doi: https://doi.org/10.1136/bmj.37972.513819.EE (Published 04 March 2004) Cite this as: BMJ 2004;328:552All rapid responses
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How did you assess the cognitive function of these middle-aged men
during their childhood?It's difficult to follow-up a cohort of patients
born in the mid 40's to present date.Which neuropsychological test battery
was used to assess cognition?The association was not clear enough.You did
not carry out computed tomography scan of their brains?Did you exclude
those with cerebral palsy at the outset?
Competing interests:
Was it a retrospective study?
Competing interests: No competing interests
EDITOR-It was interesting to read the paper of Richards et al,Cognitive
ability in childhood and cognitive decline in mid-life:longitudinal birth
cohort study(BMJ 2004,0:379725138). My comment:
1.It is well known among lay people in Muslim countries that those who
can recall Koran by heart in their childhood (holy book of Muslim) very
rarely suffer from dementia.
2.The other thing is that those who continue to work after the age of 65 are
less likely to suffer from cognitive decline.
Thanking you,
Yours sincerely,
AK.Al-Sheikhli,MRCPsych ,DPM
Competing interests:
None declared
Competing interests: No competing interests
Regression to the mean
Richards et al present convincing evidence of an association between
higher cognitive ability in childhood and slower rate of cognitive decline
in mid-life. However, I am less convinced by their claim of an association
between adult cognitive ability and rate of mid-life cognitive decline,
and suspect that the observed association could be due to a statistical
artefact.
I note that adult cognitive ability was assessed by the NART at age
53, and that cognitive decline was assessed by the change in memory or
search speed tests between ages 43 and 53. If the NART scores are
correlated with the other cognitive scores, then the observed association
could be a result of the well-known statistical phenomenon of regression
to the mean. In other words, anyone who was having an unusually bad day
when tested at age 53 might have shown low scores on the NART test and
also low scores on the memory or speed tests. This could lead to a
spurious association between NART scores at age 53 and rate of decline
between 43 and 53, even if there is in reality no association.
Perhaps there was some subtle trick in the authors’ statistical
analysis to account for this effect, but if so I couldn’t see what it was
from reading the paper (which could, of course, be a function of my own
mid-life cognitive decline). Was the possibility of regression to the mean
taken into account in the analysis, or could it be the cause of the
observed negative association between adult IQ and rate of cognitive
decline?
Competing interests:
None declared
Competing interests: No competing interests