Time, Age, Gender, and Test Practice Effects on Children’s Olfactory Performance: a Two-Year Longitudinal Study

Changes in olfactory perception observed in cross-sectional studies may not reflect actual ongoing change within individuals. The aim of the present study was to assess intra-individual as well as inter-individual variation in olfactory scores in pre-schoolers across five waves over a 2-year period.

The participants were 157 children (79 boys) aged 5.8?±?0.6?years at initial testing. We repeatedly examined the effects of time, age, gender, test practice, operationalised as the number of sessions attended and the intervals between them, and influence of school entry on identification, discrimination, and threshold Sniffin’ Sticks scores. Data imputation was performed due to missing data.

In non-imputed data, odour identification and discrimination were higher in girls. More odours were also correctly identified by children who had attended fewer sessions in shorter intervals. In imputed data, in addition to these effects, odour identification and discrimination increased further into the study and were higher in children who were older at initial testing and those who had started attending school. Schoolchildren also had lower thresholds than pre-schoolers. However, both the significant and non-significant effects were generally small.

We observed mainly small effects of gender and test practice on odour identification and discrimination, whereas intra-individual variation appeared only after data imputation.

It is likely that olfactory development over time needs to be observed for longer than 2?years.