BACKGROUND:Transient global amnesia (TGA) is characterised by a sudden onset of anterograde amnesia lasting up to 24 hours. One major differential for TGA is transient epileptic amnesia (TEA), which typically lasts<1h. However TGA can also be short in duration and little is known about the time-trends, characteristics and prognosis of TGA cases lasting<1h. METHODS:We compared the clinical features of TGA ascertained in two independent cohort studies in Oxfordshire, UK (Oxford cohort 1977-1987 vs. Oxford Vascular Study- OXVASC 2002-2018) to determine the time-trends of clinical features of TGA. Results were validated in another independent contemporary TGA cohort in Italy (Northern Umbria registry-NU 2002-2018). We compared the risk factors, clinical features and long-term prognosis (major cardiovascular events-MaCE, recurrent TGA and seizure/epilepsy) of patients presenting with episodes lasting <1h vs. those ≥1h. RESULTS:Overall 639 TGA patients were included (114 Oxford cohort, 100 OXVASC, 425 NU). Compared to the original Oxford cohort, there were more cases with TGA lasting <1 hour in OXVASC (n/% 32/32.0% vs. 9/8.8%), and in NU (11.8% vs 8.8% in Oxford cohort). In both OXVASC and NU, patient age, vascular risk factors and clinical features were largely comparable between those with TGA<1h vs. those lasting ≥1h. Moreover, there was no difference in the long-term risk of seizure/epilepsy or MaCE between TGA<1h vs. TGA≥1h. CONCLUSIONS:Short-duration TGA episodes (<1h) are not uncommon and are more frequent now than in earlier studies. The clinical features and long-term prognosis of short-duration TGA did not differ from more typical episodes lasting≥1h.