Early lens aging is accelerated in subjects with a high risk of ischemic heart disease: an epidemiologic study

Lens fluorescence and skin fluorescence in the Copenhagen Twin Cohort Eye Study: Covariates and heritability

Lens and skin fluorescence are related to the systemic accumulation of advanced glycation end products, which is accelerated in diabetes. We have examined lens fluorescence and skin fluorescence in healthy adult twins. The study enrolled twins aged median 59 years from a national population-based registry. Diabetic individuals were excluded from analysis. The interrelatedness between fluorescence parameters and relations between fluorescence and age, current HbA1c and smoking pack years were examined using correlation tests and mixed model linear regression analyses. Broad-sense heritability was analyzed and compared for lens fluorescence, skin fluorescence and HbA1c. Lens fluorescence and skin fluorescence were crudely interrelated (R = 0.38). In linear regression analyses, age explained a larger fraction of the variance in lens fluorescence (R2 = 32%) than in skin fluorescence (R2 = 20%), whereas HbA1c explained smaller variance fractions (R2 = 3% and 8%, respectively) followed by smoking pack years (4% and 3%, respectively). In multivariate analyses, age, HbA1c and smoking pack years combined explained more of the variance in lens fluorescence (R2 = 35%) than in skin fluorescence (R2 = 21%), but the influence of HbA1c on lens fluorescence was not statistically significant (p = .2). Age-adjusted broad-sense heritability was 85% for lens fluorescence, 53% for skin fluorescence and 71% for HbA1c in best fitting heritability models. Both fluorescence parameters increased with age, current glycemia and cumulative smoking. Lens fluorescence was found to be a predominantly heritable trait, whereas skin fluorescence was more influenced by environmental factors and closer related to current glycemia. The results suggest that skin fluorophores have a faster turn-over than lens fluorophores.

Microvascular retinopathy in subjects without diabetes: the Inter99 Eye Study

PURPOSE

Retinal vascular lesions such as microaneurysms and haemorrhages, while typical of diabetic retinopathy, are also seen in subjects without diabetes where they are associated with elevated cardiovascular mortality. In theory, these lesions could be a consequence of past hyperglycaemia. We examined the prevalence and risk factors for retinopathy, including lens fluorescence, a biomarker of cumulative life-time glycaemia in adults without diabetes.

METHODS

Cross-sectional population-based study of 711 subjects without diabetes (WHO 1999 criteria) aged 30-60 years, including oral glucose tolerance testing, clinical and laboratory examinations, non-invasive ocular lens fluorometry and seven-field fundus photography.

RESULTS

  Retinopathy was present in 8.3% (CI(95) 6.3-10.3%) of subjects. Higher systolic blood pressure (SBP) (p = 0.032), increasing body mass index (BMI) (p = 0.014) and wider waist circumference (p = 0.014) were significantly associated with retinopathy after adjusting for age and sex. Retinopathy was not significantly related to long-term, short-term or current glycaemia (lens fluorescence, HbA(1c) , fasting plasma glucose). In the multivariate analysis, the odds ratio (OR) for retinopathy in subjects with SBP ≥160 mmHg compared to subjects with SBP <130 mmHg was 2.68 (CI(95) 1.07-6.70, p = 0.036) and in subjects with BMI ≥30 compared to subjects with BMI < 25 the OR for retinopathy was 2.14 (CI(95) 1.01-4.57, p = 0.049) when adjusting for both variables, age, sex, the presence of impaired glucose tolerance and impaired fasting glucose.

CONCLUSION

 Retinopathy in subjects without diabetes was associated with hypertension and obesity. The study found no evidence that microvascular retinopathy in non-diabetic subjects was a consequence of past hyperglycaemia.

Sleep disturbances are related to decreased transmission of blue light to the retina caused by lens yellowing

STUDY OBJECTIVES

Sleep pattern and circadian rhythms are regulated via the retinohypothalamic tract in response to stimulation of a subset of retinal ganglion cells, predominantly by blue light (450-490 nm). With age, the transmission of blue light to the retina is reduced because of the aging process of the human lens, and this may impair the photoentrainment of circadian rhythm leading to sleep disorders. The aim of the study was to examine the association between lens aging and sleep disorders.

DESIGN

Cross-sectional population based study.

SETTING

The study was performed at the Research Center for Prevention and Health, Glostrup Hospital, Denmark and at the Department of Ophthalmology, Herlev Hospital, Denmark.

PARTICIPANTS

An age- and sex-stratified sample of 970 persons aged 30 to 60 years of age drawn from a sample randomly selected from the background population.

INTERVENTIONS

Not applicable.

MEASUREMENTS AND RESULTS

Sleep disturbances were evaluated by a combination of questionnaire and the use of prescription sleeping medication. Lens aging (transmission and yellowing) was measured objectively by lens autofluorometry. The risk of sleep disturbances was significantly increased when the transmission of blue light to the retina was low, even after correction for the effect of age and other confounding factors such as smoking habits, diabetes mellitus, gender, and the risk of ischemic heart disease (P < 0.0001).

CONCLUSIONS

Filtration of blue light by the aging lens was significantly associated with an increased risk of sleep disturbances. We propose that this is a result of disturbance of photoentrainment of circadian rhythms.

Cumulative glycemia and microangiopathy in subjects with impaired glucose regulation in the Inter99 study

AIMS

To assess cumulative glycemia, microvascular characteristics, and associated risk factors for diabetes in subjects with impaired glucose regulation.

METHODS

Cross-sectional, population-based study comprising systemic characteristics in 6487 participants and ocular characteristics in 970 participants.

RESULTS

Lens fluorescence, a quantitative index of life-long cumulative glycemia, was increased by 7.5% (CI(95) 0.37-15.1%) in subjects with impaired fasting glucose, by 13.0% (CI(95) 5.5-21%) in subjects with combined impaired fasting glucose and impaired glucose tolerance (IFG+IGT), and by 11.8% (CI(95) 6.8-17.1%) in subjects with screen-detected diabetes compared to normoglycemic subjects, adjusted for age, sex, and smoking. The prevalences of microalbuminuria and retinopathy were significantly increased in subjects with screen-detected diabetes after adjusting for age, sex and systolic blood pressure. The prevalences of associated risk factors for diabetes were elevated in all categories of abnormal glucose regulation compared to normoglycemic subjects.

CONCLUSIONS

Life-long cumulative glycemia, microangiopathy, and associated risk factors for diabetes were significantly elevated in subjects with abnormal glucose metabolism, most prominently in subjects with IFG+IGT and in subjects with screen-detected diabetes. These results provide the first objective evidence that cumulative glycemic load is increased at the earliest stage of impaired glucose regulation.