Updated Sniffin’ Sticks normative data based on an extended sample of 9139 subjects

The current study provides updated norms for the “Sniffin’ Sticks” olfactory test based on a large sample. The present data obtained from 9139 subjects corroborate previous normative findings—which is noteworthy given that approximately two-thirds of the data are newly added to the database, as compared to the previous version from 2007 [15]. We observed similar values of the tenth percentile in all age groups, although the exact comparison cannot be made due to the more narrow age categories in the present study, e.g., previously, age group A was 5–15 years, whereas in the current study we present data for age groups A (5–10 years) and B (11–20 years).

With the current investigation we found the hyposmia cutoff point of 30.75 points in the reference group aged 21–30 years. Hitherto, the hyposmia cutoff score was 30.5 points [15] and in the proposed normative dataset, the same exact value of 30.5 points is the tenth percentile value of age group D (31–40 years). This 0.25 point difference between age groups C and D is likely to result from the division of the previously investigated group aged 16–35 years into two decade-wide age groups C (21–30 years) and D (31–40 years). The diagnosis of hyposmia remains to some extent an arbitrary decision, as the cutoff point of 30.75 has been established with respect to group C aged 21–30 years, representing the overall best smelling subsample. By a shift of perspective, individual scores may also be regarded in relation to the corresponding sex and age groups. We would like to give an example of how to interpret a patient’s score: A female subject aged 55 years obtained a threshold score of 4.5 points, an identification of 14 points and a discrimination score of 13 points, resulting in a TDI score of 31.5 points. According to the tenth percentile of her age group, her outcome would be “hyposmia” for the threshold test and “normosmia” for identification and discrimination. As, by definition, the more general, overall TDI sumscore overrides separate subtest results, her final diagnosis would be “normosmia”.

Importantly, changes of the tenth percentile TDI scores observed in the youngest and oldest age groups provoke the question about a deepened and updated analysis of the changes in olfactory performance [18]. Current data indicated the most pronounced loss in olfactory threshold, whereas olfactory discrimination and identification are, for one, tested with suprathreshold concentrations of odors and are, in addition, largely determined by individual experience and conscious cognitive processes which decrease at a slower pace over time. The pronounced decrease of odor thresholds with age supports the idea that it represents damage to the periphery of the olfactory system to a stronger degree than diminished odor identification and discrimination which are more strongly related to higher cognitive processes (for discussion see: [19‐21]).

The relatively high percentage of children under 10 years with hyposmia is considered to be due to test difficulty rather than low olfactory function. Therefore, age-appropriate olfactory tests are necessary and have indeed been developed [9, 11, 22].

Our extended data further corroborated earlier reports on decreased olfactory abilities in age groups over 55 years [18, 23‐27]. The apparent decrease in olfactory performance in seniors older than 60 raises the question about dynamics of olfactory loss with age.

“Functional anosmia”—a residual ability to perceive odors with limited usefulness in daily life—was found in a total of 0.45% of the subjects, and it was mostly prevalent in the oldest age groups, with the most visible decrease of function from age 70 years upwards. These subjects either have no olfactory function left at all or exhibit a modest ability to perceive, discriminate or identify odors insufficient for enjoyable experience of foods and drinks or the ability to detect environmental hazards such as gas, fire or food gone bad. However, age itself should not be considered a cause of olfactory loss but rather an accompanying factor of neurodegenerative diseases, drug side-effects, etc. [28, 29].

The incidence of 0.45% of participants with functional anosmia is low compared to epidemiological studies (e.g., [30]). One reason may be that the TDI score is used as the basis to establish the diagnosis of “functional anosmia”. However, using an odor identification score below eight points to determine the fraction of this population returns the number of 3.4%. It has to be considered that all subjects entering the study maintained to have a fully functional olfactory system. Yet, we found a meaningful proportion of subjects scoring in the range of hyposmia or functional anosmia, who seem either not to be aware of their olfactory dysfunction or not to be bothered by it. Finally, it must be kept in mind that the majority of the currently described population is young and healthy. Therefore no conclusions regarding epidemiology of olfactory loss in the general population can be made based on this work.

We observed sex-related differences with women outperforming men. Available empirical reports on this issue are inconclusive, with some studies pointing to a female advantage in olfactory tasks over males [15, 31, 32] but others failing to confirm this difference [33]; for review see: [34]. In our large sample, we observed the main effects of sex indicating that females obtained significantly higher scores than males—however, the difference in mean TDI scores calculated for both groups was rather small (1.3 points). In such a large sample size, even very small absolute differences become significant. In any case, the current study confirmed that sex-related differences are present but may be small; in other words, if sex-related differences are observed at all, it is typically women outperforming men.

We present updated norms for “Sniffin’ Sticks” based on a large sample of 9139 subjects. With this extended sample we found hyposmia to be defined at less than 30.75 points of TDI score in the group aged 21–30 years. Observed effects of sex and age corroborate previous norms by showing a significant decrease of olfactory abilities with age with a most pronounced increase between age 5–20 years and a most pronounced decrease at the age of 60–71 years.