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Certain illnesses may put you at risk of having another—a so-called partner condition—come along for the ride. For instance, high blood pressure may help boost diabetes risks. 

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Researchers aren’t always certain why some medical issues appear to lead to others. It may be that one disease causes another or that underlying health factors create circumstances that make it more likely you’ll develop both, says Leslie Farland, Sc.D., assistant professor of epidemiology and biostatistics at the University of Arizona. Here, how to handle four partner problems.

Endometriosis and Melanoma

In endometriosis, uterine lining tissue grows elsewhere in the body, sometimes causing pain. Melanoma, a cancer of the cells that color the skin, is the most serious of all skin cancers. Its rates have been rising for the past 30 years.

In recent decades, small studies have suggested an association between the two conditions. Last year, a study that followed almost 100,000 women for 18 years, published in Cancer Causes & Control, confirmed that link. Only 32 women with endometriosis developed melanoma during the study, but that was 64 percent higher than the rate for women without endometriosis.

“Understanding the reasons for this connection is an area of active research,” says study co-author Farland. The conditions may share a genetic pathway, or it may be that endometriosis affects hormone or inflammation levels in the body, increasing melanoma risks.

To reduce your risk: Be sun smart. Generously apply sunscreen (at least SPF 30) to exposed skin regardless of season or cloud cover; wear protective clothing; seek out shade, especially between 10 a.m. and 4 p.m.; use extra caution near reflective surfaces like water, snow, and sand; and shun tanning beds. 

Metabolic Syndrome and Kidney Stones

Metabolic syndrome means you have at least three of the following: hypertension, high triglycerides, high blood sugar, too little “good” HDL cholesterol, and excess abdominal fat. It hikes diabetes, heart disease, and stroke risks. Kidney stones are hard, painful deposits inside the kidney.

There’s a long-known link between metabolic syndrome and kidney stones, says Mantu Gupta, M.D., professor at the Icahn School of Medicine at Mount Sinai and chairman of urology at Mt. Sinai West and St. Luke’s hospitals, all in New York City.

And a 2016 review in the Journal of Endourology found that those with more metabolic syndrome traits were more likely to develop the stones. The cause of the association isn’t known yet, but some think metabolic-syndrome-related damage to tiny blood vessels in the kidneys may play a key role—creating inflammation that may lead to stone formation, Gupta says.

To reduce your risk: Reverse metabolic syndrome. Lose weight if appropriate, exercise regularly, and avoid smoking. Your doctor may also recommend medication to help normalize blood pressure, blood sugar, and/or cholesterol. And drink enough water to produce plenty of pale urine each day.

Migraine and Cardiovascular Disease

Migraines are recurring headaches that can cause throbbing and sometimes debil­it­at­ing pain on one or both sides of the head. Cardiovascular disease (CVD) refers to several illnesses related to the heart and blood vessels, often caused by a buildup of plaque on artery walls.

Observational studies over the years have linked migraines with heart disease, says Amy Pollak, M.D., a cardiologist at the Mayo Clinic in Jacksonville, Fla. And last January, a study published in BMJ that followed half a million Danish adults for 19 years found higher rates of heart attack, atrial fibrillation, or stroke in people with migraines than in the general public.

CVD risks are thought to be highest in women and people who have auras (bright or flashing lights or muscle weakness before or during migraine). Theories about the cause abound. According to Pollak, CVD risk factors may be more prevalent in those with migraines.

To reduce your risk: Protect your heart. Consume a heart-healthy diet, exercise regularly, avoid smoking, get enough sleep, manage stress, and control blood pressure and blood sugar levels. And make sure your doctor is aware that you’re prone to migraines when assessing your heart disease risk, Pollak advises.

Rheumatoid Arthritis and Gum Disease

Rheumatoid arthritis (RA) is a progressive autoimmune disease marked by painful, swollen joints. Gum or periodontal disease causes gum infections that can lead to sore mouth, bleeding, chewing problems, and tooth loss.

Dentists long ago noticed that people with rheumatoid arthritis were more likely to have gum disease—and vice versa. “People with periodontal disease are at higher risk of RA, and people with RA are at greater risk of having more advanced periodontal disease,” says Mark Bartold, Ph.D., D.D.Sc., professor emeritus at Australia’s University of Adelaide and co-author of a 2013 review of 19 studies on the topic.

The reason for the connection between the two conditions is unclear, but there’s some evidence that treating periodontal disease improves certain markers for RA.

To reduce your risk: Attend to your dental health. Brush twice a day with fluoride toothpaste; clean between your teeth regularly with dental floss, an interdental brush, a floss pick, or a water flosser; quit smoking; and visit your dentist as recommended for checkups and cleanings.

Editor’s Note: This article also appeared in the December 2018 issue of Consumer Reports On Health.