An Italian population-based study of the prevalence of olfactory impairment

The loss of sense of smell decreases quality of life and may contribute to the failure in recognizing hazardous substances. Given the relevance of olfaction in the daily life, it would be important to recognize undiagnosed olfactory dysfunction in order to prevent these possible complications. Up to now, the prevalence of smell disorders in Italy is unknown because of a lack of epidemiological studies. The aim of the present study is to present the current data on the prevalence of olfactory dysfunction in an Italian sample to provide random, population-based data of olfactory dysfunction in adults, based on psychophysical testing and to relate dysfunction to age, sex, cognitive abilities, cognitive reserve and depression level. A total of 703 participants (mean age: 50.6; SD: 19.5; range: 18-94) from eight different Italian regions took part in the study. The sample was stratified in proportion to sex and six age groups: 18-29 (N = 127); 30-39 (N = 115); 40-49 (N = 105), 50-59 (N = 115), 60-69 (N = 89); >70 (N = 152). Olfactory function, cognitive abilities, cognitive reserve and depression were assessed respectively with: “Sniffin’ Sticks” Identification Test, Montreal Cognitive Assessment, Cognitive Reserve Index and the Beck Depression Inventory. Additionally, sociodemographic data, medical history, and health-related lifestyle information was collected. About 38% of our sample presented olfactory impairments. Multiple regression analysis revealed that age, sex, cognitive abilities, cognitive reserve and depressive symptoms explained a total of 28.5% of the variance in olfactory scores. Higher odor identification scores were associated with female sex, lower age, higher level of cognitive functioning, higher cognitive reserve but, surprisingly, more depressive symptoms.