Olfactory impairment and the risk of cognitive decline and dementia in older adults: a meta-analysis
Zirong Chen, Hongbo Xie, Linyin Yao, Yongxiang Wei
Abstract
The prediction of the impact of olfactory impairment on cognitive decline in older adults has been different among different age groups. This meta-analysis sought to estimate the predictive power of olfactory impairment on cognitive decline during follow-up in older adults of different ages. A medical literature search was carried out using these databases for eligible studies: MEDLINE, COCHRANE and EMBASE. Studies recording olfaction and cognition detection at the beginning and end of the follow-up were included in the preliminary screening. The medical records of older adults without cognitive impairment at the beginning of the follow-up were taken into account in this analysis. Raw data was extracted in order to estimate the relative risk and the corresponding 95% confidence interval (95% CI). Subgroup analysis of age was performed to eliminate the effect of age on the results. Statistical heterogeneity was measured using the I2 index and Cochran's Q test. Eight studies were enrolled in this analysis (3237 events and 13165 participants), and the pooled relative risk for the 70–80 years old subgroup was 2.00 (95% CI = 1.79–2.23). Relatively, there is a higher risk of cognitive impairment at the end of follow-up in younger adults with olfactory impairment at the beginning of follow-up. The length of follow-up has a little effect on the relative risk.