Adults with diabetic retinopathy are nearly twice as likely to develop Parkinson’s disease as those without the condition, according to a study published in The Journal of Clinical Endocrinology & Metabolism.
“Studies have shown an association between diabetes and Parkinson’s disease,” Seung Eun Lee, MD, MS, of the department of internal medicine, Asan Medical Center, University of Ulsan College of Medicine in Seoul, South Korea, and colleagues wrote. “The retina is a part of the central nervous system; it was proposed that diabetic retinopathy and Parkinson’s disease share common pathophysiology of dopamine deficiency. However, no epidemiological studies have investigated the relationship between these two diseases.”
To evaluate the association between diabetic retinopathy and incident Parkinson’s disease, researchers examined patient data related to health checkups, prescription use and diagnostic codes from the Korean National Health Insurance Service database between 2005 and 2013. Researchers identified 14,912,368 participants with no history of Parkinson’s disease. Participants were divided into three groups: no diabetes (n = 13,568,931; mean age, 48.5 years; 53.5% men; mean BMI, 23.7 kg/m2), diabetes without diabetic retinopathy (n = 1,222,897; mean age, 57.2 years; 60.7% men; mean BMI, 24.9 kg/m2) or diabetes with diabetic retinopathy (n = 120,540; mean age 61 years; 48.2% men; mean BMI, 24.5 kg/m2) and were followed until the date of Parkinson’s disease incidence, death or Dec. 31, 2013. Researchers used Cox proportional hazards regression analysis to calculate the HR for Parkinson’s disease, depending on diabetes or diabetic retinopathy status. Variables including age, sex, BMI, smoking, heavy drinking, exercise, hypertension, dyslipidemia and severity of diabetes were included in the analysis.
Researchers found that the incidence rates for Parkinson’s disease among those with no diabetes, diabetes without diabetic retinopathy and diabetic retinopathy were 2.74, 8.39 and 15.51 per 10,000 person-years, respectively. After adjusting for age, sex, BMI, smoking, alcohol use, exercise, hypertension, dyslipidemia, end-stage renal disease, peripheral artery disease, fasting plasma glucose and insulin use, patients with diabetic retinopathy had a higher incidence of Parkinson’s disease (HR = 1.75; 95% CI, 1.64-1.86) than those with diabetes but no diabetic retinopathy (HR = 1.33; 95% CI, 1.29-1.38).
The results of the study suggest that diabetic retinopathy is an independent risk factor for Parkinson’s disease, but more studies are needed to investigate the mechanism of increased risk, according to the researchers.
“Physicians should pay attention to the possibility of [Parkinson’s disease], in addition to diabetic neuropathy, when patients with [diabetic retinopathy] complain of motor and neurologic symptoms, even in young patients,” the researchers wrote. – by Melissa J. Webb
Disclosures: The authors report no relevant financial disclosures.