Ocular biomarkers for cognitive impairment in nonagenarians; a prospective cross-sectional study

Background

Ocular imaging receives much attention as a source of potential biomarkers for dementia. In the present study, we analyze these ocular biomarkers in cognitively impaired and healthy participants in a population aged over 90 years (= nonagenarian), and elucidate the effects of age on these biomarkers.

Methods

For this prospective cross-sectional study, we included individuals from the EMIF-AD 90+ study, consisting of a cognitively healthy (N = 67) and cognitively impaired group (N = 33), and the EMIF-AD PreclinAD study, consisting of cognitively healthy controls aged ≥60 (N = 198). Participants underwent Optical Coherence Tomography (OCT) and fundus photography of both eyes. OCT was used to asses total and individual inner retinal layer thickness in the macular region (Early Treatment Diabetic Retinopathy Study circles) as well as peripapillary retinal nerve fiber layer thickness, fundus images were analyzed with Singapore I Vessel Assessment to obtain 7 retinal vascular parameters. Values for both eyes were averaged. Differences in ocular biomarkers between the 2 nonagenarian groups were analyzed using linear regression, differences between the individual nonagenarian groups and controls were analyzed using generalized estimating equations.

Results

Ocular biomarkers did not differ between the healthy and cognitively impaired nonagenarian groups. 19 out of 22 ocular biomarkers assessed in this study differed between either nonagenarian group and the younger controls.

Conclusion

The ocular biomarkers assessed in this study were not associated with cognitive impairment in nonagenarians, making their use as a screening tool for dementing disorders in this group limited. However, ocular biomarkers were significantly associated with chronological age, which were very similar to those ascribed to occur in Alzheimer’s Disease.

Innovative technology shows impact of glycaemic control on peripheral retinal vessels in adolescents with type 1 diabetes

AIMS/HYPOTHESIS

Retinal imaging enables non-invasive microvasculature assessment; however, only central retinal vessels have been studied in type 1 diabetes. Peripheral smaller vessels have a major haemodynamic role and may differ from central vessels in their response to the diabetic milieu. We hypothesise that diabetes has a greater impact on peripheral retinal vessels vs central vessels.

METHODS

Retinal photographs from adolescents (n = 736; age 12-20 years) with type 1 diabetes were graded (Singapore I Vessel Assessment) with vessel calibres measured in the 'central zone' as central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively) and the 'extended zone' as mean width of arterioles and venules (MWa and MWv, respectively). Multivariable linear regression was used to explore associations between vessel calibres and HbA_1c, diabetes duration, sex and BP.

RESULTS

Mean ± SD age was 14.1 ± 1.5 years, HbA_1c was 8.5 ± 1.3% (69.4 ± 14.1 mmol/mol) and median diabetes duration was 4.9 years (interquartile range 3.1-7.6 years). Wider MWa was associated with HbA_1c (β 0.01 [95% CI 0.004, 0.03]), longer diabetes duration (0.07 [0.02, 0.13]) and higher systolic BP (0.04 [0.02, 0.05]). MWv was associated with HbA_1c (0.02 [0.009, 0.03]) and higher systolic BP (0.04 [0.03, 0.06]). CRAE was associated with longer diabetes duration (0.93 [0.58, 1.28]) and higher systolic BP (-0.28 [-0.37, -0.19]). CRVE was associated with longer diabetes duration (0.91 [0.42, 1.41]) and higher systolic BP (-0.20 [-0.33, -0.07]). Girls had wider vessels (for all four calibre measurements).

CONCLUSIONS/INTERPRETATION

In adolescents with type 1 diabetes, higher HbA_1c is associated with adverse changes to peripheral smaller retinal vessels but not central vessels. The predictive value of retinal vascular imaging should be evaluated using longitudinal data.