Subjective cognitive impairment: When to be concerned about ‘senior moments’

In light of this research, we believe patients with SCI and other risk factors for AD, such as a family history of AD, may be at higher risk of further cognitive and functional decline compared with individuals with ARCD and no AD risk factors. Therefore, patients with SCI and other risk factors for AD (Table 2)^15-19 may benefit from annual follow-up to determine if cognitive problems have progressed to MCI or AD.

SCI may be a response to subclinical alterations in neurobiology—a phenomenon known as reverse causality.²⁰ Biomarkers, such as cerebrospinal fluid levels of ß-amyloid and phosphorylated tau, and amyloid imaging using positron emission tomography may help identify AD in SCI patients.²¹ In these patients, SCI is a misnomer because the cognitive impairment is real—not “subjective”—but current tests are not sensitive enough to detect the cognitive decline the patient has recognized. This group of patients should be differentiated from individuals who may perceive typical cognitive aging (ARCD) as pathologic and complain about it. In the future, biomarkers may help differentiate these 2 groups.

Table 2

Factors that increase SCI patients’ risk for dementia

Mild cognitive impairment

MCI is similar to SCI because MCI patients may present with complaints of memory decline and other cognitive difficulties²² but neither condition is associated with significant impairment of daily activities.²³ The key difference is that patients with MCI demonstrate impaired performance on objective cognitive tests whereas SCI patients do not.²⁴ In our experience, office-based tests do not reliably differentiate the 2 conditions because many patients with SCI may show mild impairment in tests such as the Mini-Mental State Exam (MMSE)²⁵ but comprehensive neuropsychological testing reveals no objective cognitive deficits. Neuropsychological testing is essential to reliably differentiate SCI from MCI.

The distinction between SCI and MCI is clinically relevant because evidence suggests that MCI patients have a near-term risk of developing dementia, particularly AD.^22,23 In a longitudinal study of 76 individuals with MCI, 12% of patients progressed to AD each year compared with 1% to 2% of healthy older adults.²⁶ Patients with MCI are at increased risk of delirium (especially during hospitalization), falls, medication errors, and difficulty managing their finances.²⁴ Older adults with MCI also have increased mortality compared with older adults with normal cognitive functioning.²² Both SCI and MCI should be differentiated from mild dementia. Common dementias in older adults include:

• AD dementia
• Vascular dementia (may occur with or without AD)
• Lewy body dementia
• Frontotemporal dementia
• Parkinson’s disease dementia.

By definition, all dementia types are associated with impaired ability to perform daily activities and cognitive decline.²⁷

Assessing cognitive complaints

Evaluation of older adults’ cognitive complaints should begin with a thorough history to elicit symptoms of anxiety, depression, physical complaints, and any associated functional decline; a physical exam; and a comprehensive mental status examination. This initial evaluation should be followed by routine and specific investigations as indicated (Table 3).^22,24,28,29

In a 6-year study of 100 older adults with and without objective evidence of memory decline, both groups showed similar rates of cognitive complaints.³⁰ Also, researchers found no relationship between individuals’ perception of their cognitive functioning and performance on neuropsychological testing. Mood, education level, and apolipoprotein E epsilon 4 genotype status also did not correlate with participants’ subjective cognitive complaints. These findings highlight the need for objective test data to determine whether older adults’ memory complaints reflect pathologic changes in cognition. After a thorough diagnostic workup, some patients complaining of memory decline will have no detectable evidence of cognitive dysfunction or an identifiable cause. However, others may have identifiable causes of memory impairment (Table 4)^28,29,31,32—which could be treated—some will have MCI, and others may be in an early stage of dementia.

Table 3

Investigation of older adults with SCI