Many former leaders of the world's nine nuclear-armed nations were impaired by health conditions while in office, raising concerns over their decision-making abilities while they had access to nuclear weapon launch codes, a study from the University of Otago, New Zealand, has found.

The study analyzed the health information of 51 deceased leaders of nuclear-armed countries: China, France, India, Israel, North Korea, Pakistan, Russia, the United Kingdom and the United States. Eight of the leaders died from chronic disease while still in office, five from heart attacks or strokes. Many of the leaders had multiple serious health issues while in office, including dementia, personality disorders, depression and drug and alcohol abuse.