The brain reaches its maximum weight at about 20 years of age and shows a progressive loss of weight due to atrophy totalling approximately 100grams for individuals in their nineties. This cell loss is not evenly distributed in the central nervous system. The cerebral cortex shows a larger weight loss than the brain stem, and some nuclei show age-related losses whereas others appear to remain stable throughout life (Kiernat, 1991). Research indicates working memory is located in the pre-frontal area of the brain. When age-related changes occur, the executive function difficulties can be observed by an inability to master new types of tasks in new situations. In other words there is a lack of flexibility and an inability to trouble shoot, react appropriately or quickly in dangerous or technically difficult situations.

Cognitive impairment. . . increases substantially as people age. The primary degenerative process remains untreatable and survey data reports indicate that the prevalence of gradual loss of memory roughly doubles after the age of 65 years with every 5 years of age reaching a level of at least 16% in persons 80 and over (Breteler et al., 1992; Katzman & Kawas, 1994), and there is evidence that it can reach 47% among those 85 and older (Evans et al., 1989).  In 2003, Haaland KY, Price L, Larue noted following research using a standardization sample from the WMS-III (N = 1250), which varied in age from 16 to 89, that there was a decreases in performance.  This was first seen in the fifth decade with gradual deterioration until the eighth decade when there was another precipitous drop. The results they achieved suggested that functions that are more dependent on the frontal lobes are more vulnerable to aging than those that are more dependent on the temporal lobes.

The provision of most aged care services is based on the assumption that people function at the same cognitive level. Therefore it is often assumed that people who can talk well (verbal-propositional information stored in long-term memory) and use well-learnt habits (visual spatial information stored in procedural memory) to provide for their own personal needs are capable of new learning. This is not the case.

In all people, skills, habits and routines are learnt over a period of many years and are hard wired into their procedural memories. Everyone has, without consciously thinking about it, established patterns for how they achieve day-to-day tasks, with each person doing these tasks in a different way. However for people who are advanced in age, simple habits often cannot be re-learnt or adapted because some elderly are incapable of learning new techniques and are unable to establish a new habit. Trying to change a skill learnt over a lifetime is difficult for some and impossible for others. The constant ongoing changes that are rapidly occurring with globalisation, including banking and information technology are beyond many peoples' ability to understand or learn new procedures, which in turn has lead to resentment and anger.

Clearly, there can be no memory if learning has not occurred first, and learning has no meaning without memory (Levy, 1998).

Causes of age-related changes in cognitive dysfunction

An emerging body of literature is investigating the relationship between cognition, health and illness in older adults. The major hypothesis is that the cognition in healthy older adults remains relatively intact, whereas cognition in those with chronic disease processes shows precipitous declines (Schaie, 1990; Launer et al. 1995). Empirical evidence lends support to this premise, particularly with reference to chronic disease processes such as hypertension, cardiovascular disease and diabetes (Siegler & Costa, 1985; Elias, Elias & Elias, 1990; Elias et al., 1993; Schaie, 1990; Sands & Meredith, 1992). The implication here is that changes in cognitive function (typically, memory) might more usefully be viewed as potentially modifiable manifestations of disease and/or manifestations of changes in physiological functioning (Levy, 1998).  In 2000, Myers JS, Rauch GM, Rauch RA, Haque A, Crawford K concluded that TIAs, hypertension, hyperlipidemia, smoking, and male gender accelerate cerebral degenerative changes, cognitive decline, and dementia in many people over the age of 71 years.  In 2001, Knopman D, Boland LL, Mosley T, Howard G, Liao D, Szklo M, McGovern P, Folsom AR, this group of researchers from the Department of Neurology, Mayo Clinic came to the conclusion following a study involving nearly 11,000 people, that hypertension and diabetes mellitus were positively associated with cognitive decline over a 6 year period of time, particularly in the late middle-aged population (47 to 57 year old subgroup). The researches concluded that interventions aimed at hypertension or diabetes that begins before age 60 might lessen the burden of cognitive impairment in later life.

 There is ample evidence that the more serious cardiovascular conditions (atherosclerosis and cerebrovascular disease) increase the risk and extent of cognitive decline. Not only has it been shown that untreated hypertension is inversely related to cognitive functioning, that is, those with high untreated blood pressure scored lower on cognitive tests (Elias et al., 1993); but there is also evidence that medications that prevent subtle brain changes due to hypertension, low blood pressure, and elevated blood sugar have an important impact on the occurrence of cognitive impairment (Launer et al., 1995).

It may well be that healthy older adults who maintain an active physical and intellectual life will show little or no loss of cognitive abilities unless (or until) confronted with serious disease (Levy, 1998).

It should be made clear that a cognitive disability should not be confused with mental illness, even though it manifests in brain pathology.

Theory base

In 1965 Claudia Kay Allen, Associate Professor of the University of Southern California, developed The Allen Theory on Cognitive Disabilities. Her theory is now known as The Functional Information Processing Model. Ms Allen is also the Medical Reviewer for the Blue Cross of California and she has been instrumental in establishing a separate new National Medicare CPT Code: 975X1 in America (In process). Her work is closely linked to the World Health Organisation (WHO) 2000 ICIDH-2: International Classification of Human Functioning, Disability and Health (Universal Approach) situated in The Components of Health.

The Functional Information Processing Model is used widely throughout The United States. There the AOTA National Certification Board's 1999 Survey of Work Practices found that 55,000 Occupational Therapists and 65,000 Occupational Therapy Assistants are now using this model. In Texas, USA, the San Antino State Hospital and other institutions use this model exclusively. In the state of Delaware, Ivelisse Lazzarini OTR/L and an Allen Authorised Cognitive Advisor was appointed the state's Aged Care Advisor. Her previous position was with DVA/USA Salisbury VAMC, North Carolina, where she developed and organised many seminars for staff on the Allen conceptual framework.

This theory has been extensively scientifically researched to prove its credibility.

The Allen's model…has been adopted by Medicare (USA) to document the functional consequences of cognitive impairment in older adults (Allen et al., 1989; HCFA, 1989).

A chapter written by Linda Levy, MA, OTR/L, FAOTA in the publication, "Cognition and Occupation in Rehabilitation; Cognitive Models for Intervention in Occupational Therapy" by Noomi Katz, PhD, OTR. 1998, states "This chapter discusses the application of Allen's Cognitive Disabilities Model for rehabilitating cognitively impaired older adults as a benchmark treatment strategy for this now recognised population".

"Quality research also requires the use of outcome measures with established reliability and validity. We are now seeing the development of valid and reliable outcome measures, such as the Allen Cognitive Level Test (ACL)" (Keller & Hayes, 1998; Robyn Hayes, 2000).

Claudia Allen is the author of five books (two in the process of being revised) on cognition and has been invited to write articles on the subject for many joint publications. Articles in over 100 journals have been published verifying the validity of the theory and research has been completed in a variety of different settings with people from varying cultures.

The Allen Battery of assessments provides consistent, reliable ad quality documentation that demonstrates the level/mode/patterns of performance in all areas of a resident's life. This information is documented as behaviour, assistance required, goals to be met and the safety issues that need to be addressed.

Once an aged person has been assessed the person's cognitive level/mode/patterns of performance remains unchanged, unless there is a further episode of illness, which could result in a noticeable inability to attain pre-episode cognitive ability to perform everyday tasks. Further episodes of illness can cause further deterioration in cognitive ability.

References

Allen, C.K. (1982). Independence through activity: The practice of occupational therapy (psychiatry). American Journal of Occupational Therapy, 36. 731-739

Allen, C.K. (1985). Occupational therapy for psychiatric diseases: Measurement and management of cognitive disabilities. Boston: Little, Brown.

Allen, C.K. (1987b). Eleanor Clarke Slagle Lectureship-1987: Activity, occupational therapy's treatment method. American Journal of Occupational Therapy, 41, 563-575.

Allen, C.K., Foto, M., Moon-Sperling, T., & Wilson, D. (1989). A medical review approach to Medicare outpatient documentation. American Journal of Occupational Therapy, 43, 793-800.

Allen, C.K., Earhart, C.A., & Blue, T (1992). Occupational Therapy Treatment Goals for the Physically and Cognitively Disabled. Rockville, MD: American Occupational Therapy Association.

Allen, C.K. & Blue, T (1998). Cognitive Disabilities Model: How to Make Clinical Judgements. In N, Katz (Ed.) Cognition and Occupation in Rehabilitation: Cognitive Models for Intervention in Occupational Therapy. The American Occupational Therapy Association, Inc.

Allen, C.K. (1999). Structures of the Cognitive Performance Modes. Allen Conferences, Inc.

Breteler, M.M.B., Claus J.J., Van Duijin C.M., Launer L. J. & Hofman, A. (1992). Epidemiology of Alzheimer's disease. Epidemiology Review, 14, 59-82.

Evans, D.A., Funkenstein H.H., Albert, M.S., Scherr, P.A. & Cook, N.R. (1989). Prevalence of Alzheimer's disease in a community population of older persons. Journal of the American Medical Association, 262, 2551-2556.

Elias, M. F., Elias J.W. & Elias, P.K. (1990). Biological and health influences on behavior. In J.E.Birren & K.W.Schaie (Eds.), Handbook of the psychology of aging (3rd ed). NY: Academic Press.

Elias, M.F.& Marshall P.H. (Eds) (1987). Cardiovascular disease and behavior. Washington, DC: Hemisphere.

Elias, M.F., Wolf. P.A., D'Agostino, R.B., Cobb, J. & White, L. (1993). Untreated blood pressure is inversely related to cognitive functioning: The Framingham Study. American Journal of Epidemiology, 138, 353-364.

Launer, L., Masaki, K., Petrovitch, H., Foley, D., & Havlik, R. (1995). The association between midlife blood pressure levels and late-life cognitive function. JAMA, 272 (23), 1846- 1851.

Levy, L.L. (1998). Cognitive Changes in Later Life: Rehabilitative Implications. In N, Katz (Ed.) Cognition and Occupation in Rehabilitation: Cognitive Models for Intervention in Occupational Therapy. The American Occupational Therapy Assoc., Inc.

Haaland KY, Price L, Larue A. (2003). What does the WMS-III tell us about memory changes with normal aging?  Journal Int Neuropsychology Society, Jan: 9(1):89-96

Hayes, R.L. (2000). Evidence-based occupational therapy needs strategically-targeted quality research now. Australian Occupational Therapy Journal (2000) 47, 186-190.

Health Care Financing Administration (HCFA). (1989). Outpatient occupational therapy Medicare part B guidelines (DHHS Transmittal No. 55). In Health Insurance Manual. Baltimore: HCFA.

Katzman, R., & Kawas, C. (1994). The epidemiology of dementia and Alzheimer's disease. In R.D. Terry, R. Katzman, & K.L. Blink (Eds.), Alzheimer Disease. New York: Raven Press.

Kiernat, J. (1991). Occupational Therapy and the older adult. A clinical manual. An Aspen Publication, Aspen Publishers, Inc. Maryland. USA.

Knopman D, Boland LL, Mosley T, Howard G, Liao D, Szklo M, McGovern P, Folsom AR (2001).  Cardiovascular Risk Factors and Cognitive Decline in Middle-aged Adults.   Neurology.  Jan 9;56(1):42-8.

Meyer JS, Rauch GM, Rauch RA, Haque A, Crawford K. (2000).   Cardiovascular and other risk factors for Alzheimer's disease and vascular dementia.  N Y Academy of Science, Apr;903:411-23.

Sands, L. P., & Meredith, W. ( 1992). Intellectual functioning in late midlife. Journal of Gerontological and Psychological Science, 47, 81-84.

Schaie, K. W. (1990). Intellectual development in adulthood. In J.E. Birren & K. W. Schaie (Eds.), Handbook of the psychology of aging (3rd ed.). NY: Academic Press.

Siegler, I. C., & Costa, P. T. (1985). Health behavior relationships. In J. E. Birren & K.W. Schaie (Eds.), Handbook of the psychology of aging (2nd ed.). NY: Von Nostrand Reinhold