Byzantine Chronicle

The average life span of the Byzantine emperors was 52 years, without counting those with unknown birth dates or those who died before the age of 17.

The oldest emperors (at the end of their reign):

• Anastasius I, 491-518. Died at 88, reigned for 27 years
• Justinian I, 527-565. Died at 83, reigned for 38 years
• Nikephoros III, 1078-1081. Died at 80, reigned for 3 years
• Romanos I Lekapenos, 920-944. Died at 78, reigned for 24 years
• Justin I, 518-527. Died at 77, reigned for 9 years
• Basil I the Macedonian, 867-886. Died at 75, reigned for 19 years
• Manuel Palaiologos, 1391-1425. Died at 75, reigned for 34 years

The oldest emperors (at the time of their ascension):

• Justin I, 518. Emperor at 77, reigned for 9 years
• Nikephoros III Botaneiates, 1078. Emperor at 77, for 3 years
• Andronikos I Komnenos, 1183. Emperor at 65, for 3 years
• Constantine VIII, 1025. Emperor at 65, for 3 years
• Alexios V Murtzuphlos, 1204. Emperor at 64, for 3 months
• Anastasius I, 491. Emperor at 61, for 27 years
• Leo I the Thracian, 457. Emperor at 56, reigned for 17 years

The youngest emperors:

• Michael III the Drunkard, 842-867. Emperor at 2, for 25 years
• Theodosius II , 408-450. Emperor at 7, for 44 years
• Leo II, 474. Emperor at 7, for less than a year
• Constantine VII, 913-959. Emperor at 7, for 46 years
• Constantine VI the Blind, 780-797. Emperor at 9, for 17 years
• Alexios II Komnenos, 1180-1183. Emperor at 11, for 3 years
• John IV Doukas Laskaris, 1258-1261. Emperor at 8, for 3 years
• John V, 1341-1391. Emperor at 9, for 38 non consecutive years
• Constans II Pogonatus, 641-668. Emperor at 11, for 27 years
• Heraklοnas, 641. Emperor at 15, for some months

Two major groups here:
i)  emperors whose reigns were terminated with their death
ii) emperors who abdicated or were deposed before their death

i) Emperors who died as emperors

• 49 died of "natural" causes (old age, illness). At least for 5 of them, there were suspicions for poisoning.
  Most usual "natural" causes: dysentery (3 cases), dropsy (3), epilepsy (4).
• 4 died in an accident. 3 of them were hunting accidents.
• 6 were murdered. 5 of them were the victims of palace plots or trusted courtiers. One was probably killed for personal reasons (Constans II).
• 5 Died in battle (Julian, Valens, Nikephoros I, Constantine Laskaris, Constantine XI Palaiologos). Julian was actually wounded in battle and died 3 days later. Nikephoros I was killed by Bulgarians and his skull served as silver cup at the table of their king. The rest were literally disappeared in a battle.

ii) Emperors who were not emperors at the time of their death

• 7 emperors lost their throne and were killed after a revolt. 2 of them had been usurpers who were defeated by a rival emperor in a "counter-revolt" (Basiliscus, Tiberios Apsimar).
• 9 were deposed and were mutilated but not killed. 5 of them died shortly afterwards, because of their wounds: Heraklonas (641), Constantine VI (797), Michael V (1042), Romanos Diogenes (1071). 4 of them died much later, for other reasons: Leontios, Philippicos Vardanis, Isaac II, Alexios V, John IV Laskaris
• 15 were deposed or forced to abdicate. They retired (in most cases, to a monastery) and died some time after stepping down. The time varies from some months to many years. Only one of them (Isaac I Komnenos) abdicated on his own free will, for health reasons (but he lived for 2 more years). Another one -Staurakios- had to abdicate because he was seriously wounded in battle.

• In total, 23 emperors had a violent death (accidents don’t count).
• 2 emperors were taken prisoners by the enemy: Romanos V Diogenes was captured by the Seljuk Turks in Manzikert (1071) and was freed later. Alexios V Murtzuphlos after the fall of 1204 was blinded by his father-in-law Alexios III and later was arrested by the Latins and was executed (thrown from the top of the column of Theodosius)
• 13 emperors were the subject of cruel treatment. At least 4 suffered public torture before their death. 3 had suffered some form of Mutilation (nose and/or tongue slitting) and 5 were blinded. 1 was semi-blinded (one eye only - Andronikos IV). 3 emperors rose again to the throne long after their mutilation: Justinian II Rhinotmetus, Issac II Doukas and Andronikos IV.
• 2 emperors were killed by their successors personally: Phocas was decapitated by Heraklios (610) and Nikephoros II Phocas was murdered in his bedroom by a gang of conspirators under the command of his successor John I Tzimiskes (969)
• At least 17 emperors became monks before their death or after their dethronement. Not all of them on their own free will. 2 of them became bishops in Ephesus. One, John Kantakouzenos, became a prominent theologian and the protagonist of the Hesychasm movement.
• None of the Byzantine emperors committed suicide (Suicide, after all, was a cardinal sin in a theocratic state).