Aging is the single biggest risk factor for cataracts, but it is far from the only one. Diabetes, ultraviolet light exposure, certain medications, smoking, and even where you live on the map all contribute to whether and when the lens of your eye clouds over. The interplay of these factors explains why some people develop cataracts in their forties while others reach their seventies with clear lenses.
Why Aging Is the Dominant Factor
The lens of your eye is unusual tissue. Unlike most of the body, it cannot shed old cells and replace them with new ones. The proteins packed inside the lens at birth have to remain transparent for a lifetime. Over decades, those proteins accumulate damage from UV light, oxidation, and simple chemical wear. The damaged proteins begin to misfold and clump together into insoluble aggregates that scatter light instead of transmitting it, and that scattering is what we see as a cataract.1PubMed Central. Protein misfolding and aggregation in cataract disease and prospects for prevention
One of the key protective mechanisms in the lens is glutathione, an antioxidant that prevents lens proteins from cross-linking with each other. As glutathione levels decline with age, those cross-links form more readily, accelerating the buildup of opaque protein clumps.2PubMed Central. Minimizing Oxidative Stress in the Lens: Alternative Measures for Elevating Glutathione in the Lens to Protect against Cataract Research on specific lens proteins has shown that a single misplaced chemical bond between two parts of a crystallin molecule can be enough to trigger a chain reaction of aggregation under normal body conditions.3PubMed Central. An Internal Disulfide Locks a Misfolded Aggregation-prone Intermediate in Cataract-linked Mutants of Human γD-Crystallin This is why cataracts are so overwhelmingly a disease of older adults: the longer the proteins sit in the lens, the more damage accumulates and the more likely those aggregation cascades become.
Diabetes and Metabolic Syndrome
After age itself, diabetes is one of the best-established risk factors. Persistently high blood sugar drives a chemical pathway in the lens that converts glucose into sorbitol. Sorbitol draws water into the lens by osmosis, swelling its fibers and disrupting the precise protein arrangement that keeps the lens clear. This process runs alongside the oxidative stress that high blood sugar also promotes.4PubMed Central. Diabetic cataract-pathogenesis, epidemiology and treatment
The risk extends beyond diabetes alone. A large meta-analysis pooling data from ten studies and nearly 380,000 participants found that people with metabolic syndrome, a cluster that includes abdominal obesity, high blood pressure, abnormal cholesterol, and elevated blood sugar, had roughly a 28% higher risk of developing cataracts compared to those without it. The association was strongest in people over 57.5Eye. Association between metabolic syndrome and cataract: a meta-analysis Each component of metabolic syndrome may contribute through its own pathway: high blood pressure impairs blood flow to the eye, abnormal lipid levels can alter the lens membrane, and elevated blood sugar feeds the sorbitol pathway already described. A study of the Korean population confirmed that abdominal obesity and impaired fasting glucose were independently linked to age-related cataracts even when analyzed separately from the full syndrome.6PubMed Central. Association between metabolic syndrome and age-related cataract
Ultraviolet Radiation and Sunlight
Sunlight, specifically the UV-B portion of the spectrum, has been linked to cataracts since at least the 1980s, when a study of Chesapeake Bay watermen found that doubling a person’s cumulative UV-B exposure increased the risk of cortical cataract by about 60%. Those in the top quarter of annual UV-B exposure had more than three times the risk of those in the lowest quarter.7PubMed. Effect of ultraviolet radiation on cataract formation A later meta-analysis confirmed a modest but consistent elevation in cortical cataract risk among people with higher sun exposure.8PubMed Central. Correlation of Sunlight Exposure and Different Morphological Types of Age-Related Cataract
The type of cataract matters here. UV-B is most strongly tied to cortical cataracts, which start at the outer edge of the lens and work inward. Nuclear cataracts, the type that forms in the lens center and is most common in older adults, have a weaker link to sunlight. This is one reason a broad statement like “sunglasses prevent cataracts” oversimplifies reality: UV protection helps, but it addresses only one of many pathways leading to lens opacity.
Ionizing Radiation on the Job
UV light gets most of the public attention, but ionizing radiation (X-rays, gamma rays) is an underappreciated risk for certain workers. A study of radiology technicians and radiologists found that occupational radiation exposure to low doses was a significant contributor to cataract development.9PubMed. Risk of occupational radiation-induced cataract in medical workers A large cohort study of U.S. radiologic technologists confirmed a strong dose-response relationship: cataract risk rose steadily with cumulative occupational radiation dose, and the association remained statistically significant even when looking only at workers whose total eye-lens dose stayed below 100 milligray.10PubMed Central. Occupational radiation exposure and risk of cataract incidence in a cohort of US radiologic technologists If you work around medical imaging, nuclear medicine, or other radiation sources, consistent use of protective eyewear matters more than most people realize.
Corticosteroids and Other Medications
Corticosteroids are the medication class most closely tied to cataracts, and the link is strongest for one specific subtype: posterior subcapsular cataract, which forms on the back surface of the lens and tends to interfere with reading vision and vision in bright light. A systematic review of patients with asthma and COPD found that posterior subcapsular cataract was the most common subtype in those exposed to corticosteroids.11PubMed Central. Inhaled Corticosteroid Exposure and Risk of Cataract in Patients with Asthma and COPD: A Systematic Review and Meta-Analysis The risk is dose-dependent. In one well-known study, people whose lifetime dose of the inhaled corticosteroid beclomethasone exceeded 2,000 milligrams had more than five times the prevalence of posterior subcapsular cataracts compared to non-users.12PubMed. Use of inhaled corticosteroids and the risk of cataracts
Oral and injectable steroids carry a higher risk than inhaled forms, but even inhaled and topical steroid use raises the odds if the duration is long enough. People who need chronic steroid therapy for conditions like asthma, rheumatoid arthritis, or organ transplantation should be aware of this and have periodic eye exams.
Steroids are not the only culprit. Phenothiazine drugs, a class of older antipsychotics and anti-nausea medications, have been found to roughly triple the risk of needing cataract surgery among current users, even after accounting for diabetes and steroid use.13JAMA Ophthalmology. Exposure to Phenothiazine Drugs and Risk of Cataract Although newer antipsychotics have largely replaced phenothiazines, some are still in use, and the finding serves as a reminder that the lens is sensitive to a wider range of pharmaceutical agents than most people suspect.
Smoking and Heavy Drinking
Smoking is one of the most reliably identified modifiable risk factors for cataracts. The mechanism overlaps with aging itself: cigarette smoke delivers a heavy load of free radicals directly into the bloodstream, depleting the lens’s antioxidant defenses faster than they can be replenished. Because the evidence is so well established and widely reported in clinical guidelines, smoking is often the first lifestyle risk factor eye doctors mention.
Alcohol is more nuanced. A meta-analysis of ten studies found that heavy drinking was associated with roughly a 26% increase in cataract risk, while moderate drinking showed no clear effect in either direction.14PubMed. Different amounts of alcohol consumption and cataract: a meta-analysis The proposed mechanism centers on the byproducts of alcohol metabolism. As the body processes alcohol, it generates reactive oxygen species and acetaldehyde, both of which can modify lens proteins and promote opacity.15Scientific Reports. Alcohol use patterns and risk of incident cataract surgery: a large scale case–control study in Japan One complication in interpreting the alcohol data is that heavy drinkers are also more likely to smoke, making it hard to separate the two effects cleanly. When studies adjusted for smoking, the alcohol-cataract link weakened somewhat.
Nearsightedness
Myopia, especially high myopia, is a risk factor that surprises many people. The Blue Mountains Eye Study found that people with high myopia had about three times the odds of developing nuclear cataracts compared to those with normal vision. For posterior subcapsular cataracts, the odds were even more dramatic: nearly eight times higher in highly myopic eyes.16PubMed. Myopia and the long-term incidence of cataract and cataract surgery: the Blue Mountains Eye Study The exact reason is debated, but longer eyeballs (the structural feature behind myopia) may alter the metabolic environment of the lens or expose it to more oxidative stress. Regardless of mechanism, if you have high myopia, earlier and more frequent lens monitoring is worth discussing with your eye care provider.
Sex Differences and Estrogen
Men and premenopausal women develop cataracts at similar rates. After menopause, women pull ahead, and that shift has led researchers to investigate whether estrogen plays a protective role.17Archives of Internal Medicine. Postmenopausal Estrogen Use, Type of Menopause, and Lens Opacities: The Framingham Studies Animal studies support the idea: lenses from female rats resist certain cataract-inducing signals better than lenses from males, and removing the ovaries eliminates that advantage. When estrogen is restored, the protective effect comes back.18PubMed Central. Estrogen protects lenses against cataract induced by transforming growth factor-beta (TGFbeta)
Whether hormone replacement therapy after menopause actually reduces cataract risk in humans is less settled. Some epidemiological studies have found a modest benefit among estrogen users, but the data are not strong enough to recommend hormone therapy for cataract prevention specifically. The point is more practical than prescriptive: if you are a woman in your fifties noticing vision changes, the timing may not be coincidental, and the hormonal shift of menopause is part of the picture.
Diet and Antioxidants
Because oxidative damage is central to cataract formation, researchers have spent decades looking at whether dietary antioxidants can slow it down. A large prospective study following women over an average of ten years found that those with the highest dietary intake of lutein and zeaxanthin, pigments concentrated in leafy greens and eggs, had about an 18% lower risk of cataracts compared to those with the lowest intake.19JAMA Ophthalmology. Dietary Carotenoids, Vitamins C and E, and Risk of Cataract in Women: A Prospective Study A similar trend appeared for vitamin E from food sources.
These are observational findings, which means they cannot prove that the nutrients themselves caused the protection. People who eat a lot of leafy greens also tend to have other healthy habits. Still, the biological plausibility is strong enough that many ophthalmologists encourage a diet rich in fruits, vegetables, and whole grains as part of general eye health. What has not panned out is the hope that high-dose antioxidant supplements would prevent cataracts. Several large trials of vitamin C, vitamin E, and beta-carotene supplements have failed to show a meaningful benefit. Eating the foods seems to matter more than taking the pills, a theme that runs through nutrition science generally.
Air Pollution and Heavy Metals
A growing body of evidence links environmental pollutants to cataract risk. A prospective French study found that people exposed to nitrogen dioxide concentrations at or above 40 micrograms per cubic meter, the European regulatory limit, had about 46% higher odds of needing cataract surgery.20PubMed Central. Ambient air pollution exposure and incidence of cataract surgery: The prospective 3City‐Alienor study Fine particulate matter did not reach significance in that study, but the nitrogen dioxide finding adds cataracts to the long list of health outcomes tied to traffic-related air pollution.
Heavy metals are another emerging concern. Elevated cadmium and lead levels have been found in the lenses of cataract patients. Analysis of U.S. adults showed that each doubling of urinary cadmium, a marker of long-term cadmium accumulation, was associated with a 23% higher risk of cataract surgery.21PubMed Central. Cadmium and lead exposure and risk of cataract surgery in U.S. adults A recent meta-analysis also linked lead exposure to higher cataract risk.22PubMed. Exposure assessments of cadmium and lead with age-related eye disease: A systematic review and meta-analysis For most people, the main sources of cadmium exposure are cigarette smoke and certain foods grown in contaminated soil. Lead exposure has declined since the phase-out of leaded gasoline but persists through old paint, contaminated water systems, and occupational settings.
Where You Live on the Map
Geography exerts a measurable influence, mostly through UV exposure. An analysis of Medicare data in the United States found that, after controlling for age, sex, race, income, and the local supply of eye surgeons, the strongest remaining predictor of cataract surgery was latitude. For every degree of latitude you move south (toward stronger UV radiation), the probability of cataract surgery increases by about 3%.23PubMed. Cataract and latitude
Altitude adds another layer. A study in the Himalayas found that cataract prevalence was nearly four times higher in low-altitude sites with roughly 12 hours of daily sunlight than in higher-altitude sites with only seven hours, likely because low-lying valley settlements had fewer mountains blocking the sun.24PubMed. Associations among cataract prevalence, sunlight hours, and altitude in the Himalayas Meanwhile, research in China found the opposite pattern for altitude itself: lens opacities were more common at high elevation, and the risk roughly doubled with the highest UV exposure levels. That study also noted that education was inversely associated with cataracts, with literacy reducing risk by about 25% compared to illiteracy, likely reflecting a combination of indoor work, better nutrition, and greater access to eye protection.25PubMed Central. Prevalence and risk factors of lens opacities in rural populations living at two different altitudes in China These apparent contradictions dissolve when you realize that the key variable is not altitude in isolation but cumulative UV dose, which depends on sun angle, cloud cover, hours spent outdoors, terrain reflectivity, and whether people wear hats or sunglasses.
Genetics and Congenital Cataracts
Most cataracts are age-related and driven by the environmental and metabolic factors discussed above, but genetics sets the baseline vulnerability. Researchers distinguish between congenital cataracts, caused by severe mutations that damage lens proteins so badly that cataracts appear at birth or in early childhood, and age-related cataracts, where genetic variants merely destabilize proteins enough to make them more susceptible to environmental insults over a lifetime.26PubMed Central. Inherited cataracts: Genetic mechanisms and pathways new and old
For age-related cataracts, the genetic contribution is real but diffuse. Twin studies suggest that roughly a third to half of the variation in cataract risk is heritable. No single gene dominates. Instead, dozens of common variants each nudge the odds a little, many of them in genes that code for the crystallin proteins of the lens or the enzymes that protect them from oxidative damage. If a parent or sibling developed cataracts at an unusually young age, it is reasonable to mention that to your eye doctor, but there is no genetic test that meaningfully predicts individual cataract risk for the general population.
Cataracts in Other Species
Cataracts are not uniquely human. Dogs develop them, often as a complication of diabetes or as an inherited condition in breeds like the Boston Terrier and Cocker Spaniel. Horses get them. Even fish do. Research on young coho salmon found that transferring freshwater fish to seawater before they had completed their normal physiological transition caused cataracts in every surviving fish, likely due to osmotic shock to the lens.27Aquaculture. Ocular cataract and seawater adaptation in salmonids Farmed salmon in particular have been plagued by cataracts related to diet, water conditions, and rapid growth, a problem serious enough to attract attention from the aquaculture industry. The vulnerability of the lens across so many species underscores a fundamental design constraint: transparent tissue built from long-lived proteins is inherently fragile, and any organism whose lens proteins accumulate damage faster than they can be repaired is on a path toward opacity.