Image courtesy of Prevention

Whether you've been married for half a century or dating for a few months, a partner's lagging sex drive can shake any relationship. And while there are a number of reasons your libido may have gone MIA (more on that in a bit), new research makes a troubling connection between a man's erectile issues and his heart health.

An Australian study of more than 95,000 middle-aged men found a direct link between erectile dysfunction and heart disease, a link that persisted even among men with no history of cardiovascular problems. According to the study, the risk of heart disease and premature death increases with the severity of a man's ED--minor erectile difficulties could signal a relatively mild heart issue, while severe erectile dysfunction ups a man's risk of coronary artery disease by 60%.

"Rather than causing heart disease, erectile dysfunction is more likely to be a symptom or signal of underlying 'silent' heart disease," says lead study author Emily Banks, PhD, a professor of epidemiology and public health at Australian National University. And the advice is unequovical: "For men who are having problems getting or maintaining an erection, it means taking action by seeing a health professional and asking for a heart check."

If you're the one struggling with sexual issues, on the other hand, your low libido could also be a sign of an underlying health issue. Talk to your doctor to see if any of these five conditions could be at play:

Diabetes: Uncontrolled blood sugar levels can lead to low sex drive and sexual discomfort, including increased vaginal dryness and recurrent yeast infections in women. In fact, women taking insulin are twice as likely to report problems with lubrication and orgasm compared to non-diabetic ladies.

Menopause: The natural dip in estrogen that accompanies menopause can make sex uncomfortable for women. If you're experiencing vaginal dryness during or just before menopause, ask your doctor to check hormone levels and make a lubricant suggestion.

Underactive thyroid: It slows down metabolism, causes hair loss, and can throw a wrench in a healthy sex life. If you find yourself too tired for anything, including sex, an underactive thyroid might be to blame. Your risk for thyroid problems increases with age, so have your doctor test your levels.

Depression: Depression alone can cause a decreased interest in sex, but common antidepressants used to treat depression can also put a damper on sex drive. In fact, a lessened interest in sex is one reason people stop taking their antidepressants, says Ron Rosenberg, MD, an OB-GYN and psychiatrist at William Beaumont Hospital in Royal Oak, MI. Ask your doctor about switching to an antidepressant that has fewer side effects.

More: Smart Ways To Increase Your Sex Drive

Low testosterone: It's the hormone that fuels sexual desire and enhances pleasure in both women and men. And if your body isn't producing enough of it, you could be experiencing low levels of sensation, a slow response to your partner's come-ons, and an overall lagging sex drive.

More: Is Your Birth Control Killing Your Libido?

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