On 3 December 1960, Korolev suffered his first heart attack. During his convalescence, it was also discovered that he was suffering from a kidney disorder, a condition brought on by his detention in the Soviet prison camps. He was warned by the doctors that if he continued to work as intensely as he had, he would not live long. Korolev became convinced that Khrushchev was only interested in the space program for its propaganda value and feared that he would cancel it entirely if the Soviets started losing their leadership to the United States, so he continued to push himself.