Table 1.

Results of studies of the epidemiology of olfactory disorders

Population	n	Age (range)	Gender (% Female)	Smell Test	Major findings	Strengths	Weaknesses	Reference
Skövde Sweden	1387	20–80 +	51.77 %	self-report, SOIT	-poorer-than normal odor detection sensitivity was 15.3% (self-report) -the prevalence of olfactory dysfunction was 19.1%; 13.3% had hyposmia and 5.8% suffered from anosmia	population-based data across all ages; representative of the general adult Swedish population	self-report	26; 27
Skövde Sweden	1713	13–80 +	52.13 %	self-report	=3.9% of the general population aged 13 years and older report having had parosmia (4.0% of the adults and 3.4% of the teenagers).	added a teenage population; assessed qualitative disorders	teenage data may be less reliable?	28
The Beaver Dam Study WI, USA	2491	53–97	58%	SDOIT	-prevalence of impaired olfaction was 24.5%	extensive information available on potential risk factors	limited generalizability to minority groups?	13
The Beaver Dam Offspring Study WI, USA	1993	21–84	54.4%	SDOIT	-prevalence of olfactory impairment was low at 3.8% in this primarily middle-aged cohort -this increased with age (from 0.6% in those <35 years to 13.9% among those ≥65 years)	one of the few longitudinal studies extensive information available on potential risk factors	may not be representative?	29
National Health Interview Survey (NHIS) USA	80,000	≥18	*	home interview	-1.4% of US adults complained of an olfactory problem -almost 40% of those who reported a chemosensory problem were ≥65 years	large sample	likely underestimates actual prevalence due to self-report?	30
KNHANES South Korea (2009)	7306	20–95	56.7%	questionnaire	-prevalence of subjective olfactory disorders was 4.5%	large sample provided a clinical association between olfactory dysfunction and mental health	self-report, not strictly controlled	31
KNHANES South Korea (2010–201 1)	11972	≥19	50.74 %	questionnaire	-prevalence of olfactory dysfunction was 5.0%	large sample provided a clinical association between olfactory dysfunction and mental health	unable to distinguish degrees of smell disturbance; cross-sectional	32
NSHAP, USA	3005	57–85	56.7%	Odor ID test	-prevalence of severe olfactory dysfunction was 2.7%	nationally representative sample	only a small percentage of the variance is explained	33
NSHAP, USA	1436	57–85	51.7%	Odor ID test	-odor identification is one of the strongest predictors of 5-year mortality	well controlled	no cause of death, no information on younger ages, acquired causes	1
OLFACAT Catalonia, Spain	9348	5–91	65.7%	Odor ID test	-prevalence of dysfunction was 19.4% - a significant age-related decline in odor detection	large sample	potential bias in this non-random sample; lack of ethnic diversity, socio-cultural class	36
Memory and Aging Project (MAP) IL, USA	481	mean age 80.6 ± 7.0	72.6%	CC-SIT	-prevalence of olfactory impairment was 55.3% -impaired odor identification in old age is associated with impaired global cognition	high rate of participation in follow-up outstanding cognitive assessment	select cohort of convenience; fewer women included	42
Memory and Aging Project (MAP) IL, USA	1162	mean age 79.7 ± 7.7	74.5%	CC-SIT	-difficulty identifying familiar odors in old age is associated with increased risk of death	well characterized cohort	select cohort; fewer women included	45
Blue Mountains Eye Study Australia	1636	≥60	58.1%	SDOIT	-prevalence of olfactory impairment was 27.0%.	high participation rate high follow-up rate	cross-sectional, potential bias?	46
Bet.ula Sweden	1906	45–90	54.46 %	SOIT	-a gradual/linear deterioration in cued odor identification across the adult life span	good demographic and cognitive variables, sample size	cross-sectional	48
Honolulu-Asia Aging Study (HAAS) HI, USA	2267	71–95	0%	CCSIT	-olfactory deficits associated with the presence of incidental Lewybodies and PD	longitudinal design, large sample size with excellent follow-up, well-validated test instruments	men only; older age focused	39

^*not provided