Introduction: Antiphospholipid syndrome (APS) leads to damage accrual that impairs long-term functional status. The Damage Index for Antiphospholipid Syndrome (DIAPS) captures the damage accrual in thrombotic APS, but it is not known whether it correlates with mortality. We aim to determine whether early damage and its kinetics predicts long-term mortality in thrombotic APS.Methods: Retrospective analysis of 197 thrombotic APS patients (2006 Sydney classification criteria) followed at a tertiary centre in London up to 43 (median 10) years. The disease onset was the time the first thrombotic event related to APS was diagnosed. Early damage refers to damage present at six months after the disease onset. Early DIAPS increase refers to the increase of at least one point from the initial DIAPS within the first five of illness. We used logistic, uni and multivariable Cox regression models to analyse risk factors affecting mortality.Survival was analysed using the Kaplan-Meier method.Results: The median age at APS onset was 40 (IQR 51-28) years, with a female (71%) and primary APS (66%) preponderance. Caucasian ethnicity was the most prevalent (72%), followed by Asian (10%), Afro-Caribbean (9%) and other (9%).Damage developed in 143 (73%) patients with a median DIAPS of 1 (IQR 2-0) at the last visit. Early damage was present in 69 (35%) patients. We identified 23 fatalities (12%). Deceased patients had higher last DIAPS (p=0.012) but similar early DIAPS score (p=0.318) compared to those who survived. Secondary APS (HR 3.07, p=0.009), male gender (HR 3.14, p=0.008) and age at APS onset ≥40 years (HR 5.34, p=0.001) were risk factors for death. Early damage was not associated with death (HR 1.65, p=0.231). Early DIAPS increase (n=53/181, 29%) was 3 associated with death (HR 5.40, p<0.001), even after adjusting individually for APS category (secondary, p<0.001), gender (male, p<0.001) and age at APS onset (≥40 years, p=0.006). Having a first arterial event was associated with early damage (p<0.001), but not with early DIAPS increase (p=0.539) nor with the risk of death (p=0.151).Conclusion: An increase of at least one point on DIAPS in the first five years after disease onset, but not early damage, predicts of mortality regardless of the nature of the first thrombotic event, gender, APS category and age.