For most people, older adulthood is associated with some decline in memory and in some aspects of cognitive function. These are age-related changes  that are widely expected, understood, and accepted by the general public. Some individuals, however, experience changes that they perceive as extending beyond that expected as part of normal aging. Such a ‘feeling’ or ‘sense’ that something is wrong can be hard to describe to family, friends, and clinicians and although an individual’s perceived changes in memory and cognition can be corroborated and confirmed by formal objective testing and from the reports of others  and diagnosed as mild cognitive impairment or dementia, formal examination can also fail to reveal objective evidence of decline [3,4].
Individuals with perceived changes in memory and cognition in the absence of objective evidence are commonly given a ‘diagnosis’ of subjective cognitive decline (SCD) . As evidence increasingly reveals SCD as a risk factor for the development of dementia, particularly Alzheimer’s disease (AD) [4-7] and a stage in a neurodegenerative disease potentially suitable for interventional strategies, research and clinical priority has focused on investigating the relationship between SCD and the development of dementia.
The emphasis on the relationship between SCD and the development of dementia has, however, tended to overshadow the fact that SCD is etiologically heterogeneous and that for only a proportion of individuals does it represent a prodromal stage of dementia. Causes are varied and include sleep disorders, depression, psychiatric conditions, neurologic and medical disorders, substance use, and medication and can be related to personality type . There are also people for whom etiology cannot be determined; this is evinced from research studies and clinical investigations in which participants with SCD have met exclusion criteria for known potential causes of SCD but failed to develop dementia. Another factor receiving little attention is the propensity of SCD to diminish and cease to exist in some cases .
Another potentially important but relatively sparsely investigated issue, is the potential for SCD, irrespective of etiology, to inflict significant detrimental effects upon well-being, active aging, quality of life resulting in individual, social, financial, and public concern. Related to this issue, the question I want to raise is whether the emphasis on the relationship between SCD and dementia could actually dissuade individuals from seeking clinical investigation of perceived changes in memory and cognition. In addition to the ‘worried well’ (those who might fit the criteria for SCD in the absence of known etiology for example) are individuals too afraid to initiate clinical investigation for fear of discovering incipient dementia despite the fact that the cause may be treatable.
In a recent paper, Mendonça et al.  suggested ‘…care should be taken not to overemphasize SCCs (subjective cognitive complaints). Facing the heterogeneous and ambiguous meaning of SCC, they should be looked at as symptoms and we should avoid classifying them as a condition. The creation of a diagnostic category for SCC could lead to an increase in futile diagnostic examination and testing. Participants would be exposed to unnecessary stress for a symptom that ultimately will not lead to any disorder or early death’ [page 6, column 2, paragraph 4].
Arguably, however, diagnostic examination and testing is not futile if it leads to the increased diagnosis of treatable causes of SCD. Can one assume that a diagnosis of SCD evokes greater stress than living with a disorder that can profoundly affect life quality and that could potentially, but unknown to the individual concerned, be treated? Surely this is about personal choice? It is clear that despite the current lack of a cure for dementia many individuals contact their general practitioner and actively request investigation of their perceived memory problems. Should they be refused this for fear of causing distress? Furthermore, significant numbers of individuals with SCD volunteer for research, part of which can involve full diagnostic profiling; again indicative in some individuals of a need to know more about their ‘condition’.
Many years ago, similar debates were held about the early diagnosis and screening of cancer, and what is clear today is that although the possibility of successful treatment has improved enormously and many screening opportunities are now available to facilitate the early diagnosis of cancer, not everyone chooses this option, and where screening programs are not available and cure less likely, individuals still seek diagnosis and information about their signs and symptoms. What is profoundly clear, therefore, is that individuals differ widely in their approach to disease, illness, early diagnosis, and the extent of information they wish to be imparted to them. What does appear to be important, and to empower many people, is freedom of choice.
References  Bishop NA, Lu T, Yankner BA (2010) Neural mechanisms of ageing and cognitive decline. Nature464, 529-535.  Caselli RJ, Chen K, Locke DE, Lee W, Roontiva A, Bandy D, Fleisher AS, Reiman EM (2014) Subjective cognitive decline: self and informant comparisons. Alzheimers Dement10, 93-98.  Jessen F, Amariglio RE, van Boxtel M, Breteler M, Ceccaldi M Chételat G, Dubois B, Dufouil C, Ellis KA, van der Flier WM, Glodzik L, van Harten AC, de Leon MJ, McHugh P, Mielke MM, Molinuevo JL, Mosconi L, Osorio RS, Perrotin A, Petersen RC, Rabin LA, Rami L, Reisberg B, Rentz DM, Sachdev PS, de la Sayette V, Saykin AJ, Scheltens P, Shulman MB, Slavin MJ, Sperling RA, Stewart R, Uspenskaya O, Vellas B, Visser PJ, Wagner M; Subjective Cognitive Decline Initiative (SCD-I) Working Group (2014) A conceptual framework for research on subjective cognitive decline in preclinical Alzheimer’s disease. Alzheimers Dement10, 844-852.  Mitchell AJ, Beaumont H, Ferguson D, Yadegarfer M, Stubbs B (2014) Risk of dementia and mild cognitive impairment in older people with subjective memory complaints: meta analysis. Acta Psychiatr Scand130, 439-451.  Rönnlund M, Sundström A, Adolfsson R, Nilsson L-G (2015) Subjective memory impairment in older adults predicts future dementia independent of baseline memory performance: Evidence from the Betula prospective cohort study. Alzheimers Dement, doi: 10.1016/j.jalz.2014.11.006.  Blackburn DJ, Wakefield S, Shanks MF, Harkness K, Reuber M, Venneri A (2014) Memory difficulties are not always a sign of incipient dementia: a review of the possible causes of loss of memory efficiency. Br Med Bull112, 71-81.  Reisberg B, Schulman MB, Torossian C, Leng L, Zhu W (2010) Outcome over seven years of healthy adults with and without subjective cognitive impairment. Alzheimers Dement6, 11-24.  Studer J, Donati A, Popp J, von Gunten A (2014) Subjective cognitive decline in patients with mild cognitive impairment and healthy older adults: Association with personality traits. Geriatr Gerontol Int14, 589-595.  Canevelli M, Blasimme A, Vanacore N, Bruno G, Cesari M (2014) Issues about the use of subjective cognitive decline in Alzheimer’s disease research. Alzheimers Dement10, 881-882.  Mendonça MD, Alves L, Bugalho P (2015) From subjective cognitive complaints to dementia: Who is at risk: A systematic review. Am J Alzheimers Dis Other Dement, doi: 10.1177/1533317515592331.