Ask an answerable question (PICO):
Mild cognitive impairment is the transitional step between cognitive impairment and dementia in older adults, defined as memory deterioration that does not meet the criteria for dementia. The Cognitive Abilities Screening Instrument is a common screening tool for mild cognitive impairment, which is both expensive and time-consuming. However, the results of the screen are easily affected by educational level and age. Previous studies have shown a relationship between cognition and olfactory sensation in older adults. Therefore, this study aimed to determine whether olfactory testing could identify mild cognitive impairment in older adults. This testing may be helpful to identify more objective and easier ways to screen for cognitive impairment to detect and prevent dementia.
The Method and Analysis of Literature Review:
An evidence-based method was adopted to set the PICO question and keywords using synonymous and MeSH terms. Bollean logic “AND” and “OR” were used to search the English databases. A total of 453 articles were selected from the Embase, Medline, and Cochrane Library databases. After excluding repeated and irrelevant articles (studies not investigation mild cognitive impairment, lacking olfactory assessment, lacking a control group of non-healthy older adults, subjects younger than 65 years old, medical article, full text not available), four cohort studies were included.
Critical Appraisal:
Based on the Oxford Centre for Evidence-Based Medicine, four studies were identified as level 3, which met 7-9 requirements of the Joanna Briggs Institute checklist. All articles explored the relationship between decline in olfactory function and mild cognitive impairment. The population in all four articles was extracted from community and corresponded with our PICO setting. Finally, all of the articles involved diagnostic questions, and the results indicated a significant correlation between decline in olfactory function and mild cognitive impairment. Furthermore, the results support that a decline in olfactory function can predict the development of mild cognitive impairment.
Results, Conclusions and Recommendations:
The results of this study showed that a decline in olfactory function could predict the development of mild cognitive impairment. Olfactory assessment is more convenient, and the assessor does not require any special training. Therefore, olfactory assessment could be applied to screen for older adults with a high risk of mild cognitive impairment. However, cognition is a multi-dimensional concept, and olfactory testing alone cannot be comprehensive. Moreover, several factors may influence olfactory testing, such as the weather, allergic problems of the nose, and other diseases (nasopharyngeal carcinoma, chronic rhinitis, etc.). Further studies are therefore needed to explore the impact of related factors in identifying mild cognitive impairment.