Daylight Saving Time Transition Linked to Shifts in Retinal Vascular Disease Risk

Clinicians may want to keep a closer eye on patients in the weeks following daylight saving time transitions, with new research suggesting the twice-yearly clock change is associated with measurable shifts in the risk of new-onset retinal vascular disease.

The nationwide cohort study, published in Scientific Reports and led by Northwestern Medicine's Rukhsana Mirza, MD, analysed insurance claims data from more than 12.6 million US adults aged 18 to 64, drawn from the Merative MarketScan Commercial Database between 2012 and 2014. Researchers tracked new diagnoses of retinal artery occlusion (RAO), retinal vein occlusion (RVO), proliferative diabetic retinopathy (PDR) and neovascular age-related macular degeneration (nvAMD) in the week and month following the autumn and spring daylight saving transitions, compared with summer and winter control periods.

Autumn "fall back" linked to lower risk, spring "spring forward" to higher risk

Using a summer control period as the reference, the study found a roughly 16-17 percent lower risk of RVO and PDR in the month following the autumn transition (adjusted hazard ratios of 0.84 and 0.83 respectively). Against a winter control, the protective effect following autumn was more pronounced and extended across all four conditions with reduced risk of RAO, RVO, PDR and nvAMD in the month afterwards.

The picture reversed for the spring transition, which involves the loss of an hour's sleep. Compared with summer controls, spring daylight saving was associated with a 34 percent increased risk of PDR and a 24 percent increased risk of nvAMD in the following month. No significant association between the spring transition and retinal vascular disease emerged when winter was used as the comparison period.

Notably, effects were concentrated in the one-month follow-up window rather than the first week, suggesting a delayed rather than immediate physiological response.

A circadian rhythm connection

Senior author Dr Mirza said the findings build on previous research linking daylight saving transitions to cardiovascular events such as stroke and heart attack, and point to the retina as a useful window into systemic vascular health.

"Our study suggests gaining an hour of sleep may be protective against disease risk," Mirza said, adding that patients reporting new visual symptoms in the period after a clock change, particularly the spring transition, may warrant closer evaluation.

Co-first author Kyle Chan, MD, a resident physician in Northwestern's Department of Ophthalmology, said the direction of the findings was consistent with existing literature on sleep loss and circadian misalignment.

"There's been literature showing that losing an hour's sleep and circadian misalignment can cause inflammatory responses and metabolic derangements," Chan said, noting a parallel evidence base suggesting the extra hour gained in autumn may confer a protective effect.

Pre-existing retinal disease a key risk factor

The study also confirmed that patients with prior diagnoses of retinal detachment, diabetic retinopathy or AMD carried substantially higher risk of progressing to vision-threatening disease around the time of a transition reinforcing the case for closer monitoring of these patients during seasonal clock changes. Older age, hypertension, hyperlipidemia and known cardiovascular disease were also identified as risk factors across the four conditions studied.

Interestingly, sleep disorders such as obstructive sleep apnoea, insomnia and narcolepsy showed no significant association with retinal vascular disease risk following the transitions, a result the authors described as unexpected given the established links between chronic sleep disruption and cardiovascular disease.

Limitations and next steps

The authors caution the findings are drawn from a US commercially-insured population aged under 65, and may not generalise to publicly insured, uninsured, or older populations, nor to patients outside the United States. The analysis was also limited to two years of data for the summer comparison and one year for the winter comparison.

Chan said he hoped other research groups would attempt to replicate the results using larger or non-overlapping datasets, including academic health databases, and extend the analysis across more years.

The authors conclude that daylight saving-related circadian disruption may represent a modifiable risk factor for microvascular retinal disease, and suggest clinicians consider counselling at-risk patients, particularly those with existing cardiovascular or retinal disease, to watch for new visual symptoms around the spring transition.