Current evidence suggests that metabolic syndrome (MetS) is associated with elevated intraocular pressure (IOP) and glaucoma, according to a review article published in the Journal of Glaucoma. In addition, mounting evidence exists that MetS is associated with a number of age-related diseases of the eye—most recently, glaucomatous optic neuropathy (GON) and elevated IOP, the most prevalent risk factor of MetS. Identifying associations between IOP, glaucoma, and MetS could allow for a novel eye disease treatment option of lifestyle modification.
MetS is classified as a constellation of correlated metabolic abnormalities that includes dyslipidemia, hyperglycemia, enlarged waist circumference, and systemic hypertension. MetS confers a 2-times increased risk of myocardial infarction and stroke, a 5-times increased risk of type 2 diabetes mellitus, and a significant risk increase for all-cause mortality.
For this review, the author found population-based studies via PubMed using the following keywords: metabolic syndrome, IOP, optic nerve, and ocular hypertension. The Korea National Health and Nutrition Examination Survey (KNHANES) is a periodically conducted, population-based epidemiological survey. Since 1998, KNHANES has included a nutritional survey, a health behavior survey, and a health examination study; an ophthalmological component of the survey was conducted from 2008 to 2013. Defining ocular hypertension as IOP >21 mm Hg, KNHANES 2008 to 2010 data showed an association between MetS and ocular hypertension in 17,160 participants >19 years of age without preexisting glaucoma.
When adjustments were made for body mass index (BMI), age, alcohol consumption, sleep duration, smoking, and regular exercise, participants with MetS were more likely to have a higher IOP compared with participants without MetS. In a group of 4875 men aged 20 years and older, IOP was found to be higher in participants with MetS; after adjustments, IOP was shown to be associated with BMI, diastolic blood pressure, systolic blood pressure, insulin resistance, fasting blood glucose, total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. IOP was also associated with MetS in a group of 4524 women, aged 20 years and older.
A South Korean Changwon community hospital evaluation between 2001 and 2013 found that patients with MetS and no intraocular disease history were more likely to have ocular hypertension compared with those without MetS. Ocular hypertension was also more common among patients with individual MetS components. In a study utilizing data from routine examinations of the Israeli Defense force with 12,747 participants (35 years to 55 years of age) without preexisting ocular hypertension or glaucoma, it was shown that those with 3 to 5 MetS components were more likely to have IOP greater than21 mm Hg than those with fewer MetS components. At Chang Gung Memorial Hospital, 10,491 Taiwanese patients (21 years to 79 years of age) with MetS had higher IOP. Higher IOP was also seen among 14,003 patients with MetS at Murakami Memorial Hospital, and IOP level increased with an increasing number of MetS components. Interestingly, IOP decreased with the medical management of triglyceride levels and systemic blood pressure. A number of studies with smaller patient populations supported these findings.
Many studies also demonstrated an association between MetS and GON. In the Korean National Health Insurance System Project, 2002 to 2013, 287,553 participants (aged 40 years and older) without preexisting glaucoma were examined and then followed longitudinally. Participants with 3 MetS components were shown to have the highest hazard ratio of glaucoma, and systemic blood pressure, BMI greater than30 kg/m2, high fasting glucose, and total cholesterol were all individually associated with a greater incidence of glaucoma. Data from a glaucoma screening program at Seoul National University Hospital from 2010 to 2011 with 18,240 participants (aged 40 years and older) showed an association between individual MetS components (including impaired glucose tolerance and hypertension) and IOP greater than 21 mm Hg and glaucoma; however, MetS as a whole was not significantly associated (P =.07).
In the 2008 to 2012 KNHANES, 14,400 participants (aged 40 years and older) with no history of glaucoma, showed that open angle glaucoma with IOP lower than 15 mm Hg was associated with MetS, dyslipidemia, stroke, ischemic heart disease, and systemic hypertension. In the 2010 to 2012 KNHANES, data from 8816 participants (aged 40 years and older) showed that glaucoma prevalence increased with an increasing number of MetS components within the total population and nonobese participants, but glaucoma prevalence was not associated with the number of MetS components in obese participants. Although there were not as many studies that examined the association between MetS and glaucoma, the association was consistent. Several of the studies excluded patients previously diagnosed with glaucoma, however, which might underestimate the association.
Further studies are needed to clarify this association. Additional metrics would include assessments of central corneal thickness and optic nerve function and structure, as well as studies to determine whether systemic treatment or lifestyle modifications targeting MetS may reduce glaucoma incidence or slow progression, the author said.
The review author concludes, “The reviewed data show associations between MetS and IOP and glaucoma. Clinicians need to be aware of this association; however, at the present time, insufficient evidence exists to recommend lifestyle modification or systemic pharmacologic therapy to modify risk for glaucoma in patients with MetS. In addition, future studies are warranted to determine whether implementing a glaucoma screening program for patients with MetS is warranted.”
Roddy GW. Metabolic syndrome is associated with ocular hypertension and glaucoma. J Glaucoma. 2020;29(9):726-731.