Mild cognitive impairment (MCI) features evidence of subjective or objective cognitive impairment along with preservation of activities of daily living (ADLs).¹ The preservation of ADLs is the core difference between MCI and dementia,² and MCI is seen as a transition period or the middle state between normal cognition and dementia.³ Although most MCI patients' cognitive function remains stable over time, some patients exhibit functional decline due to cognitive deterioration, and 5-10% progress to dementia,⁴ which is a 4-10-fold higher rate of dementia progression than among the normal elderly.⁵ Most dementia patients are diagnosed in the moderate to severe stages rather than in the early stage of the disease.⁶ Therefore, in the aging population, detecting cognitive decline in the early stage via regular screening tests may provide an opportunity for patients to receive early treatment resulting in better outcomes and lower morbidity rates.⁶

Seoul is successfully dealing with dementia by establishing a community-integrated management system for dementia comprising a metropolitan center and 25 centers in the boroughs. Since they began providing social services in 2007, they have continued to do screening and publicity to broaden awareness of dementia. The tools used for early detection of dementia in Korea are the mini mental state examination in the Korean version of the CERAD assessment packet (MMSE-KC), Korean mini-mental state examination (K-MMSE) and mini-mental state examination for dementia screening (MMSE-DS) for screening and the Korean version of the Consortium to Establish a Registry for Alzheimer's disease neuropsychological test battery (CERAD-NP-K) or Seoul Neuropsychological Screening Battery (SNSB) for a thorough workup. Dongdaemun-gu Center for Dementia, where the authors currently work, uses the MMSE-KC as a screening tool and CERAD-NP-K for close examination. The center screens individuals aged 65 years and older, a total of approximately 7,000 subjects every year. Those whose MMSE-KC results indicate cognitive impairment go through an additional close examination. Once diagnosed with MCI, individuals are categorized into the high-risk group and registered in the database to receive an annual follow-up examination. Any individual suspected of having dementia is referred to a nearby general hospital for diagnosis and to confirm the cause. Over the past 3 years at the Dongdaemun-gu Center for Dementia, the number of individuals undergoing screening was 20,833, and based on the results, 12% were suspected of having cognitive impairment underwent additional examination, and 13% were finally diagnosed with dementia. In other words, based on the Dongdaemun-gu Center for Dementia database cross-sectional assessment at April 2015, approximately 5% of the screened subjects were considered to have MCI, and 6% were diagnosed with dementia.

However, some subjects failed to visit the Center for Dementia regularly for annual screening tests. The question arose as to whether subjects who did not visit the center for annual screening were different from those who came on their appointed dates. We noticed that some subjects who were screened behindhand were diagnosed with dementia. If the conversion rate of these subjects was lower than that of those who were regularly screened, this would mean they had lower early dementia detection rates, and thus, more attention is needed for these individuals. To our knowledge, there have been no previous domestic or foreign reports on factors related to follow-up attrition for dementia screening. Therefore, with the aim of heightening the quality of the dementia management and thereby slowing and ameliorating progression toward dementia, we investigated the reasons for follow-up loss in the MCI group and analyzed their demographic factors. Through this work, we intend to provide evidence to be used to reduce follow-up loss in those at risk for dementia.

The final diagnoses of those who revisited the center after personal contact were as follows: 19.1%, normal; 64.9%, MCI; and 16.0%, dementia. In contrast, of the 24,899 subjects in the Dongdaemun-gu Center for Dementia's database who were screened from January 2008 to December 2012, 28.3% transitioned from MCI to dementia. This indicates that the follow-up loss group had a lower dementia diagnosis rate than the community-based population. Although there are limitations that the results were not statistically compared, lower dementia diagnosis dementia diagnosis rates than the community may suggest the importance of regular annual screening. In other words, compared with the follow-up group, there is a possibility that the follow-up loss group had a lower chance of detecting dementia due to lack of education of dementia, lack of regular check-up by family and friends. These findings may suggest that we need to extend outreach and education efforts regarding dementia for this population. In a study of the progression of cognitive impairment conducted in the United States, 56% of the MCI patients were stable without any further cognitive decline, 8% improved to become normal, and 35% progressed to dementia.⁹ These results suggest higher detection rates compared to our study, which seems to be related to our study's retrospective design for examining the diagnoses as well as the poor understanding and awareness of dementia in the studied population.

In the personal contacting of the 786 subjects who had not revisited the center within one year, 598 (76.1%) reported a negative response to the center's screening test. In many cases, even after numerous calls, subjects hung up the phone, and many of the subjects expected the center to prescribe medication for dementia or perform neuroimaging tests. Through the negative response of the receivers, we could indirectly suppose a lack of understanding of the disease's course and the purpose of dementia screening.

The most commonly selected questionnaire reasons for follow-up loss was “no need for checkup,” accounting for 28.2% of the answers. The core features of MCI diagnosis are 1) subjective cognitive impairment, 2) objective cognitive impairment, and 3) function preservation of activities of daily living (ADLs).¹⁰ Since subjective and objective cognitive impairment can be seen in both MCI and dementia patients, function preservation of ADLs is the main standard for differential diagnosis.²¹¹ We may assume that MCI patients with preserved function may have had no difficulties during their everyday lives and thus had no need for reexamination. It has been reported that the public interest in dementia is high, although understanding of dementia is relatively low.¹² This suggests that a poor understanding of the course of MCI may result in failure to appreciate the importance of regular screening.

The next-most common answer, “no need for checkup,” may be related to poor insight. Decreased awareness of memory impairment is often seen in Alzheimer's dementia and in MCI.¹³ Along with memory impairment, which is the main symptom of MCI patients, lacking self-awareness or “loss of self” is reported to be similar in MCI and dementia patients.¹⁴ Therefore, there is a possibility that subjects with cognitive impairment may have felt no need for checkup due to poor insight.

For the third-most frequent answer, “forgot the date,” we can consider the possibility of amnestic MCI. In a study of 296 MCI subjects, the incidence rate of the amnestic type of MCI (37.7 per 1,000 person-years) was higher than that of non-amnestic MCI (14.7 per 1,000 person-years).¹⁵ Although the current study did not distinguish MCI according to subtypes, reports that the amnestic type has a higher proportion suggest that some MCI subjects forgot to visit the center due to memory impairment.

Given prior studies suggesting that it is not subjective memory impairment, but rather the informant's report that influences progression to dementia,¹⁶ educating care-providers along with MCI patients is important. A longitudinal study of 534 subjects who were older than 70 years in age reported that, during the follow-up period, among the 38% of MCI patients whose diagnosis changed to normal, 65% were later diagnosed with MCI or dementia. It has been reported that the diagnosis of MCI is an important factor for prognosis assessment regardless of when it is diagnosed, which further supports the importance of regular screening.¹⁷

There was no statistical difference in demographic characteristics between the follow-up group who revisited the Dongdaemun-gu Center for Dementia and the follow-up loss group. This indicates that the follow-up response difference is not caused by demographic characteristics, but rather by awareness of dementia and characteristics of the disease itself.

Those who fail to attend regular follow-up visits have a lower likelihood of early diagnosis of dementia, meaning more intensive management is needed. We believe that reasons for follow-up loss may be crucial for intensive management for MCI patients, and the biggest reason reported in this study is lack of knowledge. To increase our understanding of dementia, the National Central Dementia Center has been established, and active publicity via various media is continuous. For the Dongdaemun-gu Center for Dementia, various education and publicity materials and programs have been created, and distributed and carried out by volunteers. Education materials for dementia need to be developed and continuously provided for elder people, caregivers and the general public. Considering the characteristics of MCI and dementia, the role of the caregiver is crucial. Therefore, along with active publicity, detailed education about the disease is important. Also, to publicize the importance of early screening, contact possible MCI subjects, and recruit them to participate in cognitive rehabilitation programs, the biggest challenges are securing the needed personnel and budget. These are required for the development of dementia support services.

A limitation of this study is that the response rate regarding “reasons for not visiting” was only 23.9% (188). Because 76.1% (598) refused to revisit the center when contacted, we note that the investigation of their reasons for not visiting is difficult, because the results may not represent the follow-up loss group as a whole. Similarly, because 23.9% of the subjects answered “other,” the results may not fully reflect the reasons for not visiting the center. Also, because this is a single center study, the results may not be a good representation of the target population. However, as the first study to investigate various reasons for not visiting the center for regular screening, this study makes useful contributions to the field of dementia diagnosis and management.