Adult Cognitive Function

With the single exception of a test repeated at age 26 years (reading comprehension), cognitive function was not assessed from adolescence until age 43 years, when there was a shift away from tests of intellectual ability and towards the assessment of functional cognitive performance (memory, processing speed, and motor praxis).  Some of these tests were repeated at age 53 years, with the addition at this age of a verbal ability test (the NART) to link back to related tests in childhood.

Age 26 years (1972):

The Watts-Vernon Reading Test, first given at age 15 years, was re-administered at age 26 years with an additional 10 items of increased difficulty to avoid a ceiling effect (Rodgers, 1986).

Age 43 years (1989):

Five types of cognitive test were devised by the NSHD:

  1. Verbal learning  For each of three trials survey members were shown a list of 15 words at a rate of two seconds each, then were asked to write down as many words recalled as possible.  A simple total score is available calculated as the sum of the words correctly recalled at each trial.
  2. Long-term recall A. Memory for the year, month and day of the week of the last interview; B. Memory for eight medical measures (pulse, blood pressure, lung function, height, weight, and arm, chest and abdominal circumference) taken at the age 36 (1982) interview.  A summary score is available.
  3. Visual memory  A five-item delayed (20 minutes) picture recall task.  A summary score is available but this has a strong ceiling effect.
  4. Timed letter search  This is a cancellation task using two different target letters, embedded among non-target letters, with one minute per three trials allowed, and outcome measures derived as speed, i.e. position reached at the end of each one minute interval, and accuracy, i.e. the number of target letters missed divided by speed. Summary scores are available for the mean speed for each of the three trials and an accuracy score (calculated by dividing the number of missed targets for each trial by the corresponding speed score).
  5. Motor speed and praxis  This task assessed time to move 10 pegs from one hole to an adjacent one.  Five trials were administered for each hand.  Mean speed scores are available for each hand. For distributional reasons a log transformation of the mean score is recommended.

Age 53 years (1999):

At this age the verbal learning and timed letter search tasks used at age 43 years (nos. 1 and 4 above) were re-administered, although the latter used only one trial.  In addition, a delayed recall condition was added to the verbal learning task, using an interval of approximately 90 seconds.  Tests 2, 3 and 5 above were not re-administered at 53 years.  However, four new tests were given at this age:

  1. The National Adult Reading Test (NART; Nelson & Willisson, 1991).  This is a pronunciation test involving 50 irregular words of increasing difficulty, chosen to violate conventional grapheme-phoneme correspondence rules.  To pronounce any of the words correctly the respondent must therefore be able to recognize them in their written form rather than rely on intelligent guesswork.  Thus it is effectively a test of knowledge acquisition, although it correlates with full-scale IQ. 
    N.B. the NART is traditionally scored for errors, as it is here, but this can easily be inverted by subtracting the score from 50, so as to be consistent with the direction of the other cognitive test scores.
  2. Verbal fluency  Category fluency was assessed by asking survey members to name as many different animals as possible in one minute.  The score is the total number of animals named, allowing anything belonging to the animal kingdom (from amoeba to humans), but not counting repetitions, redundancies (e.g. brown cow, spotted cow) or proper names (e.g. Rover, Kitty).
  3. Prospective memory (sometimes referred to as 'remembering to remember').  Survey members were informed that, at a later stage of the interview, they would be given an envelope and asked to write a name and address on it, and that, on receipt of the envelope, they were to remember to turn it over, seal it, and write their initials on it.  For the outcome variable a full score of 3 was achieved if both actions were completed without prompting; 2 if one action was achieved without prompting; and 0 if no action was undertaken without a prompt.
  4. Delayed verbal memory Survey members were asked to recall, without prior prompting, the name and address they wrote on the envelope used in the previous test (“John Brown, 42 West Street, Bedford”).  A maximum score of 6 was achievable for remembering all of these elements.

Age 60-64 years (2006-10):

At this age the verbal learning and timed letter search tasks, which had been used at age 43 and 53 years (nos. 1 and 4, age 43), were re-administered, although the latter used only one trial. A reaction time test was also undertaken at this age.

Age 68-70 years (2014-16):

At this age the verbal learning and timed letter search tasks, which had been used at age 43, 53 and 60-64 years (nos. 1 and 4, age 43) were re-administered, although the latter used only one trial. A finger-tapping test (number of taps with index finger in a set time, both hands tested separately) also took place.

There was also a new cognitive test given at this age:

1. Addenbrooke's Cognitive Examination-III (ACE-III). The ACE-III is an extension to the Mini Mental State Examination (MMSE), testing five cognitive domains: attention/orientation, memory, language, verbal fluency, and visuospatial skills. Scores are evaluated for each of the domains, as well as an overall score out of 100, with a higher score denoting better cognitive function. As an MMSE equivalent subset is contained within the ACE-III, a score for this can also be generated. The examination was mostly conducted using the ACEmobile app, which was installed on an ipad, providing prompts to help guide the interviewer through the assessment. Paper test sheets were used where necessary (e.g. for drawing tasks).

Research programme

Further information on the mental ageing research programme is available on the public LHA website.

Obtaining the standard adult cognitive function variables

You can obtain a list of the standard topic variables to use in an NSHD data sharing request by selecting the link at the end of this page. The XML version of the link can be sent to the LHA as part of a data sharing request. Simply use your browser's Save As facility to save the list of variables to a file on your computer. You can then email the XML version to us in support of your application, or when you fill in the data access application form and it asks which variables you need, mention the 'adult cognition standard basket' along with any others.

Please Note that the adult cognitive ability standard basket contains the most commonly-used summary variables on this topic. The variables that are most often used longitudinally, or as cross-sectional covariates, are verbal memory (word list) summaries WLT89, WLT99, WLT09 and WLT15x, and the visual search speeds CANSP189, CANSP99, VSP09 and VSP15x (note change of variable name stem). CANSP189 is used for the age 43 measure rather than the average of the visual search test speeds as the test was repeated at this age, but only took place once in later years.

For the full, detailed variable list please investigate this subject on Skylark.

More information is available on this topic - including the main variable naming conventions and some value labels.

HTML version of the standard variables to view

Download the XML for the adult cognition standard basket