Lens fluorescence in relation to glucose tolerance and genetic predisposition to type 2 diabetes mellitus in a population-based study

Purpose: The fluorescence of the lens has the characteristics of a life-long cumulative index of glycemia, and it is elevated in patients with diabetes in proportion to the duration of diabetes and the level of glycemia. Consequently, lens fluorometry should be capable of providing an estimate of prediagnostic disease duration when patients are diagnosed with type 2 diabetes. Among euglycemic subjects, first-degree relatives of patients with type 2 diabetes tend to have higher glycemia levels than subjects who are unrelated to diabetes patients. They should therefore also have the higher lens fluorescence values. Methods: The study comprised 218 Caucasian subjects in self-reported good health aged 30-88 years who were recruited from population-based studies to represent approximately equal proportions of different type 2 diabetes family history characteristics: no diabetic relative, first-degree offspring, second-degree offspring, not first-degree offspring but possibly second-degree offspring, or uncertain family history. Characterization of subjects included oral glucose tolerance testing and lens fluorometry. Results: Type 2 diabetes was diagnosed in 10 subjects (4.6% of the population) and impaired glucose tolerance in 12 subjects (5.5%). Regression analysis indicated a prediagnostic duration of type 2 diabetes of 2.7 years versus 0.1 years for impaired glucose tolerance. Neither group demonstrated significantly increased lens fluorescence compared with euglycemic subjects. Being a first-degree relative of a patient with type 2 diabetes was associated with higher lens fluorescence than having no relative with diabetes (p = 0.02). Conclusions: Population screening by fasting blood glucose measurement can advance the diagnosis and initiation of treatment of type 2 diabetes mellitus by nearly a decade, compared with previous studies of patients diagnosed in routine clinical practice. In addition to higher than normal glycemia, euglycemic subjects who are offspring of patients with type 2 diabetes also have both elevated lens fluorescence and elevated glycemia. Fasting blood glucose measurement remains the method of choice for type 2 diabetes screening.