To determine the reliability of the Social Security Death Master File (DMF) after the November 2011 changes limiting the inclusion of state records.
Secondary data from the DMF, New York State (NYS) and New Jersey (NJ) Vital Statistics (VS), and institutional data warehouse.
Retrospective study. Two cohorts: discharge date before November 1, 2011, (pre‐2011) or after (post‐2011). Death in‐hospital used as gold standard. NYS VS used for out‐of‐hospital death. Sensitivity, specificity, Cohen's Kappa, and 1‐year survival calculated.
Patients matched to DMF using Social Security Number, or date of birth and Soundex algorithm. Patients matched to NY and NJ VS using probabilistic linking.
97 069 patients January 2007‐March 2016: 39 075 pre‐2011; 57 994 post‐2011. 3777 (3.9 percent) died in‐hospital. DMF sensitivity for in‐hospital death 88.9 percent (= 0.93) pre‐2011 vs 14.8 percent (= 0.25) post‐2011. DMF sensitivity for NY deaths 74.6 percent (= 0.71) pre‐2011 vs 26.6 percent (= 0.33) post‐2011. DMF sensitivity for NJ deaths 62.6 percent (= 0.64) pre‐2011 vs 10.8 percent (= 0.15) post‐2011. DMF sensitivity for out‐of‐hospital death 71.4 percent pre‐2011 (= 0.58) vs 28.9 percent post‐2011 (= 0.34). Post‐2011, 1‐year survival using DMF data was overestimated at 95.8 percent, vs 86.1 percent using NYS VS.
The DMF is no longer a reliable source of death data. Researchers using the DMF may underestimate mortality.