Aims: Due to an ageing population and increasing survival from concurrent diseases, the burden of left-sided degenerative valvular heart disease is expected to increase over time. This study aims at determining the temporal trends in incidence rates at the population level and examines whether there are socioeconomic differences. Methods and results: A total of 133 209 patients were identified with a first-time diagnosis of aortic stenosis (AS), mitral regurgitation (MR), or aortic regurgitation (AR) in the Danish National Patient Registry in the 2000-17 period. Incidence rates (per 100 000 person-years) doubled over the period for AS (57 in 2000-02; 114 in 2015-17) and for AR (22 in 2000-02; 41 in 2015-17) and remained the same for MR (38 in both 2000-02 and 2015-17). Incidence rates increased rapidly with increasing age, most markedly for AS. Men had a higher risk of being affected [relative risk (RR) 1.69 for AS, 1.19 for MR, 1.35 for AR]. Compared to high-level education, patients with medium- and low-level education had a higher risk of being affected (RR 1.18 for AS medium level and 1.47 for AS low level; 1.03 for MR medium level and 1.14 for MR low level; 1.03 for AR medium level and 1.18 for AR low level). Conclusions: For AS and AR, the incidence rates doubled, while the incidence rates remained at the same level for MR. The risk of being affected increased with advanced age and male gender. Patients with low-level education had a higher risk of being affected compared to patients with high-level education, especially among patients with AS.