Olfactory impairment and the risk of cognitive decline and dementia in older adults: a meta-analysis

Chen, Zirong; Xie, Hongbo; Yao, Linyin; Wei, Yongxiang

doi:10.1016/j.bjorl.2020.07.009

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Brazilian Journal of Otorhinolaryngology

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Sumário

Review articles • Braz. j. otorhinolaryngol. 87 (1) • Jan-Feb 2021 • https://doi.org/10.1016/j.bjorl.2020.07.009 copy

Olfactory impairment and the risk of cognitive decline and dementia in older adults: a meta-analysis

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Introduction

The prediction of the impact of olfactory impairment on cognitive decline in older adults has been different among different age groups.

Objective

This meta-analysis sought to estimate the predictive power of olfactory impairment on cognitive decline during follow-up in older adults of different ages.

Material and methods

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 I ² index and Cochran's Q test.

Results

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).

Conclusion

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.

KEYWORDS
Olfaction disorders; Anosmia; Cognitive declines; Dementia; Meta-analysis

Author year	Participants	Duration (Y)	Samples (outcome)	Sex female (%)	Age (Y)		Education (Y)		OI		N-OI
Author year	Participants	Duration (Y)	Samples (outcome)	Sex female (%)	Mean	SD	Mean	SD	Event	Total	Event	Total
Adams DR¹⁸18 Adams DR, Kern DW, Wroblewski KE, McClintock MK, Dale W, Pinto JM. Olfactory dysfunction predicts subsequent dementia in older US adults. J Am Geriatr Soc. 2018;66:140-4. 2017	Older adults^a a Longitudinal study of a population representative of U.S. older adults.	5Y	2906 (DE)	51.1	68	7.6	-	-	58	644	66	2262
Devanand DP³⁰29 Rewa OG, Villeneuve P-M, Lachance P, Eurich DT, Stelfox HT, Gibney RTN, et al. Quality indicators of continuous renal replacement therapy (CRRT) care in critically ill patients: a systematic review. Intensive Care Med. 2017;43:750-63. 2019	Urban community	4Y	724 (CD)	65.81	75.9	2.7	11.62	2.9	36	165	22	221
				76.47	84.89	3.7	9.67	4.84	58	196	31	142
Fischer ME³¹30 Devanand DP, Lee S, Luchsinger JA, Andrews H, Goldberg T, Huey ED, et al. Intact global cognitive and olfactory ability predicts lack of transition to dementia. Alzheimers Dement. 2019. 2016	EHLS	10Y	1884 (CD)	59.1	66.7	8.4	-	-	79	323	87	1561
Graves AB³²31 Fischer ME, Cruickshanks KJ, Schubert CR, Pinto AA, Carlsson CM, Klein BEK, et al. Age-related sensory impairments and risk of cognitive impairment. J Am Geriatr Soc. 2016;64:1981-7. 1999	Community^b b A community-based longitudinal study of memory and aging.	2Y	1599 (CD)	55.61	71.45	5.34	13	2.88	28	168	116	1 431
Kristine Yaffe³³32 Graves AB, Bowen JD, Rajaram L, McCormick WC, McCurry SM, Schellenberg GD, et al. Impaired olfaction as a marker for cognitive decline: interaction with apolipoprotein E epsilon4 status. Neurology. 1999;53:1480-7. 2017	Community^c c Community-dwelling black and white older adults.	12Y	1510 (DE, white)	48.34	75.65	2.72	-	-	114	337	164	1173
			918 (DE, black)	58.17	75.42	2.79	-	-	84	263	129	655
Lipnicki DM³⁴33 Yaffe K, Freimer D, Chen H, Asao K, Rosso A, Rubin S, et al. Olfaction and risk of dementia in a biracial cohort of older adults. Neurology. 2017;88:456-62. 2013	SMAS	1.92Y	572 (CD & DE)	45.9	78.59	4.75	11.68	3.49	37	169	56	496
Rosebud O. R³⁵34 Lipnicki DM, Sachdev PS, Crawford J, Reppermund S, Kochan NA, Trollor JN, et al. Risk factors for late-life cognitive decline and variation with age and sex in the Sydney Memory and Ageing Study. PLoS One. 2013;8:e65841. 2016	Mayo^d d Participants of Prospective Mayo Clinic Study of Aging.	3.5Y	1430 (CD)	50.6	79.5	5.3	14.3	2.8	120	477	130	953
Stanciu I³⁶35 Roberts RO, Christianson TJH, Kremers WK, Mielke MM, Machulda MM, Vassilaki M, et al. Association between olfactory dysfunction and amnestic mild cognitive impairment and Alzheimer disease dementia. JAMA Neurol. 2016;73:93-101. 2014	Residents^e e A sample of 1529 participants.	10Y	1529 (CD)	55.7	61.2	11.7	11	4.1	54	300	105	1229

Author year	OT*-cutoff	CogT	OI		Multivariate logistic regression
Author year	OT*-cutoff	CogT	Adjusted RR	95% CI	Multivariate logistic regression
Adams DR¹⁸18 Adams DR, Kern DW, Wroblewski KE, McClintock MK, Dale W, Pinto JM. Olfactory dysfunction predicts subsequent dementia in older US adults. J Am Geriatr Soc. 2018;66:140-4. 2017	Validated 5-item test	Physical exam^a a Low-cost component of the physical examination, proxy interviews.	2.13	1.32-3.43	Age, gender, race/ethnicity, education, comorbidities, initial cognition
Devanand P³⁰29 Rewa OG, Villeneuve P-M, Lachance P, Eurich DT, Stelfox HT, Gibney RTN, et al. Quality indicators of continuous renal replacement therapy (CRRT) care in critically ill patients: a systematic review. Intensive Care Med. 2017;43:750-63. 2019	B-SIT - 9/12	NP-test^b b A standardized neuropsychological test battery.	2.48	1.34-4.58	Age, gender, education, language
Fischer ME³¹30 Devanand DP, Lee S, Luchsinger JA, Andrews H, Goldberg T, Huey ED, et al. Intact global cognitive and olfactory ability predicts lack of transition to dementia. Alzheimers Dement. 2019. 2016	SDOIT - 6/8	MMSE	4.18	2.68-6.51	Age, sex, education
Graves AB³²31 Fischer ME, Cruickshanks KJ, Schubert CR, Pinto AA, Carlsson CM, Klein BEK, et al. Age-related sensory impairments and risk of cognitive impairment. J Am Geriatr Soc. 2016;64:1981-7. 1999	CC-SIT - 6/12	CASI	2.92	1.76-4.86	No-adjustment
Kristine Yaffe³³32 Graves AB, Bowen JD, Rajaram L, McCormick WC, McCurry SM, Schellenberg GD, et al. Impaired olfaction as a marker for cognitive decline: interaction with apolipoprotein E epsilon4 status. Neurology. 1999;53:1480-7. 2017	B-SIT - 9/12	Modified MMSE	3.34	2.45-4.54	Age, education, APOE ɛ4 allele, depression, smoking, physical activities, BMI
			2.03	1.44-2.84
Lipnicki DM³⁴33 Yaffe K, Freimer D, Chen H, Asao K, Rosso A, Rubin S, et al. Olfaction and risk of dementia in a biracial cohort of older adults. Neurology. 2017;88:456-62. 2013	B-SIT - 9/12	International criteria^c c A panel of psychogeriatricians, neuropsychiatrists and clinical and research neuropsychologists using current international consensus criteria.	1.86	1.15-3.01	Sex, marital status, BSIT score, and age
Rosebud O. R³⁵34 Lipnicki DM, Sachdev PS, Crawford J, Reppermund S, Kochan NA, Trollor JN, et al. Risk factors for late-life cognitive decline and variation with age and sex in the Sydney Memory and Ageing Study. PLoS One. 2013;8:e65841. 2016	B-SIT - 9/12	Physician^d d Evaluated by a physician.	1.85	1.43-2.39	Sex and education, with age as the time scale
Stanciu I³⁶35 Roberts RO, Christianson TJH, Kremers WK, Mielke MM, Machulda MM, Vassilaki M, et al. Association between olfactory dysfunction and amnestic mild cognitive impairment and Alzheimer disease dementia. JAMA Neurol. 2016;73:93-101. 2014	Subjective olfaction	MMSE	2.17	1.40-3.37	Age, gender, years of education, MMSE, olfaction, and subjective olfaction

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[1] * Corresponding author. E-mail: weiyongxiang@vip.sina.com (Y. Wei).