Stress, family medical history or possibly even poison led to the death of Vladimir Lenin, contradicting a popular theory that a sexually transmitted disease debilitated the Soviet Union’s founder, a UCLA neurologist said. Dr. Harry Vinters and Russian historian Lev Lurie reviewed Lenin’s records Friday for an annual University of Maryland School of Medicine conference that examines the deaths of famous figures. The conference is held yearly at the school, where researchers in the past have re-examined the diagnoses of figures including King Tut, Christopher Columbus, Simon Bolivar and Abraham Lincoln.