Complex sentence: Gladys Lester Dull (1917? --) is according to "Diabeteshealth.com" the longest living person with type 1 diabetes (in 2007), at that time having lived with the condition for 83 years.
Split into simpler sentences: Gladys Lester Dull (1917? --) was in 2007--according to "Diabeteshealth.com"--the longest living person with type 1 diabetes. Gladys C. Lester Dull She had at that time lived with the condition for 83 years.