Cognitive performance of Canadian seniors

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Cognition is "the mental process of knowing, including aspects such as awareness, perception, reasoning, and judgement."¹  Some decrease in cognition is expected at older ages, but the decline is not uniform across all cognitive tasks or for all individuals.²  Impaired cognition can have health consequences, such as first stroke,³ falls,⁴ and institutionalization.⁵  It may reduce an individual's ability to communicate pain to health care providers,⁶ carry out instrumental activities of daily living,⁷ and cope with chronic disease symptoms, perform self-care and adhere to medication instructions.^8-10

Different aspects of cognition may have different influences on health.  Some research has suggested that memory impairment is especially important in the early detection of dementia or in the progression to Alzheimer's disease,^11,12 while other studies have found that verbal tasks¹³ and the number of impaired cognitive domains^14,15 are important.  Dysfunction in domains other than memory may be an early sign of vascular or other non-Alzheimer dementias.¹⁶  Executive function and memory may influence activities of daily living,⁷ and impaired processing speed and executive function have been associated with an increased risk of falls.^4,17

Using data from the 2009 Canadian Community Health Survey (CCHS)—Healthy Aging Cognition Module, this study examines correlates of low performance on four cognitive tasks among Canadians aged 65 or older who were living in private dwellings and who did not have Alzheimer's disease or dementia (see The data).  Low performance on these four cognitive tasks is analyzed in relation to socio-demographic characteristics and measures of health status and well-being.

The Cognition Module

Respondents to the Cognition Module of the 2009 CCHS–Healthy Aging were asked to perform four tasks.

Two tasks—immediate and delayed recall of a list of words—measured short-term verbal memory, verbal learning and post-interference recall.^22,23  Respondents were required to memorize a list of 15 common, unrelated words (for example, drum, curtain), recall them immediately, and again, after about five minutes.  The delayed recall was performed after the other cognitive tasks.

The two other tasks—semantic fluency and the Mental Alternation Test—measured executive function.  To assess semantic fluency,^24,25 respondents were asked to recall as many names as possible from a specified category (animals) in one minute.²⁶  For the Mental Alternation Test.^27-29 respondents recited the alphabet, and then counted from 1 to 26.  They then had 30 seconds in which to alternate between number and letters in the format 1-A-2-B-3-C, etc.

Five cognitive functioning categories based on normative values that adjust for age, sex and education were previously created and validated for the household population aged 45 or older.¹⁹  In this analysis, for each cognitive task, scores in the two lowest categories (about 30% of respondents) were used to identify respondents with low cognitive performance.

Low income/Living alone

The socio-economic characteristics of people aged 65 or older with low cognitive performance differed from those of people whose scores were higher.  Seniors with low scores on each task were more likely than were seniors with higher scores to be in the lowest income group (Table 1).  They were less likely to be living with a partner and more likely to live alone or to have other living arrangements, compared with seniors with moderate/high cognitive performance scores.

Table 1 Selected socio-demographic, health and well-being characteristics, by score on cognitive functioning tasks, household population aged 65 or older without Alzheimer's disease or dementia, Canada excluding territories, 2009

Chronic conditions

Vascular conditions^31,32 and psychiatric disorders^33,34 have been associated with low cognitive function.  In this study, seniors with low scores on each of the four tasks were more likely than those with higher scores to have been diagnosed with diabetes, a relationship that persisted even after accounting for socio-demographic and other health variables (data not shown).  As well, seniors with low scores on the processing speed task were more likely than those with higher scores to have heart disease.  However, no association between low performance on any cognitive task and high blood pressure or mood/anxiety disorders was apparent.  

Body mass index

A high BMI or being underweight has been associated with cognitive impairment later in life.³⁵  Although only current height and weight were reported to the 2009 CCHS, seniors with low immediate recall scores were less likely than those with higher scores to be overweight.  As well, seniors with low scores on the semantic fluency and processing speed tasks were more likely than those with higher scores to be underweight.

Falls, impairment and home care

A low score on the first recall task was associated with having had recurrent falls in the past year, but none of the cognitive tasks was associated with having had a single fall.  These findings are contrary to previous research that found both single and recurrent falls to be related to processing speed and executive function.¹⁷

For each cognitive task, seniors with low scores were significantly more likely than those with high scores to report impairment in performing instrumental and basic activities.  However, the relationship between mild or moderate/severe impairment and the first recall task, and between mild impairment and the processing speed task did not persist when socio-demographic factors and chronic conditions were taken into account (data not shown).

Low scores on each cognitive task were associated with receiving a combination of formal and informal home care; only the semantic fluency task was associated with receiving formal home care alone.  Of course, home care needs may reflect physical as well as cognitive conditions.  In multivariate analyses that controlled for socio-demographic factors, chronic conditions and aspects of physical function (pain, mobility, vision or hearing problems), the association between low cognitive performance and receiving both types of home care persisted for the second recall and semantic fluency tasks, and between receiving formal home care alone and semantic fluency (data not shown).

Social interaction

Social interaction is protective against cognitive decline, and infrequent social participation may be an early sign of declining cognitive function.³⁶  Although the temporal order cannot be established, results from the CCHS—Healthy Aging show that seniors with low scores on the first recall or processing speed task were less likely than those with higher scores to report frequent participation in community-related events, and they were more likely to be lonely, even when other factors were taken into account (data not shown).  An apparent association between loneliness and semantic fluency did not persist in multivariate models.

Self-perceived health

Regardless of how they scored on the cognitive tasks, large majorities of seniors perceived their general (at least three-quarters) or mental (over 90%) health as positive.  However, for each task, seniors with low scores were less likely than those with higher scores to rate their health positively.  This result persisted when socio-demographic factors, chronic conditions and functional impairment were taken into account (data not shown), with the exception of the second recall and perceived general health. 

Conclusion

Seniors with low scores on the various cognitive tasks were more likely than those with higher scores to experience poor outcomes on several measures of health and well-being.  The cognitive health of non-institutionalized seniors and the factors associated with it are important for health care planning and policy development.  Findings from the CCHS—Healthy Aging Cognition Module contribute to an understanding of the socio-demographic and health characteristics and the needs of seniors free of Alzheimer's disease or dementia who continue to live in private households, but whose performance on four tasks commonly used to assess cognition is low.

Acknowledgement

The content of the Canadian Community Health Survey—Healthy Aging was developed by the Health Statistics Division at Statistics Canada in consultation with Health Canada, the Public Health Agency of Canada, and experts conducting the Canadian Longitudinal Study on Aging (CLSA), an initiative of the Canadian Institute of Health Research.  Consultations included stakeholders from Human Resources and Social Development Canada and provincial and territorial health ministries.  The addition of 5,000 respondents aged 45 to 54 to the survey was funded by the CLSA.  Statistics Canada thanks all participants for their input and advice during the development of the survey.