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Invited Commentary
January 2018

Considerations When Temporal Order Is Not Clear

Author Affiliations
  • 1Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison
JAMA Ophthalmol. 2018;136(1):74-75. doi:10.1001/jamaophthalmol.2017.5212

Diabetic retinopathy (DR) and nephropathy are the main microvascular complications of diabetes, with associations reported in many cross-sectional studies.1 In moving beyond cross-sectional associations, the article by Hseih et al2 in this issue of JAMA Ophthalmology uses prospective data to evaluate the association between renal profiles and DR in persons with type 2 diabetes. While this study shows clear evidence that information about kidney dysfunction can be informative about retinopathy, it implies that kidney dysfunction precedes retinopathy. This implied temporal causal path may not make sense for retinopathy and nephropathy, which likely share some common pathways.3,4 The confounding from this common pathway could be influencing these results. When the temporal order is not clear, there are a few considerations to keep in mind during analyses.