We all know that some changes to the way your breasts look are inevitable. Aging happens. But a new study has found that other factors may be at play when it comes to determining how your breasts look later in life.

A new study, published in the Aesthetic Surgery Journal found that at least four external factors (as opposed to internal factors like age or genetics) have a significant impact on a woman's breasts. The study looked at the breasts of 161 pairs of identical twins, with an average age of 47.6 years old. Researchers took each woman's medical and personal history, and then photographed her breasts and subjectively rated them based on 16 aesthetic measures, including perkiness, skin quality and areola size. (As lead researcher Hooman T. Soltanian of University Hospitals Case Medical Center and Case Western Reserve University School of Medicine, told ABC News, there's "no objective measurement" of what makes breasts attractive. Thus these results are based on the researchers chosen criteria for attractiveness.)

Below are four factors -- daily moisturizing, history of breast cancer, hormone replacement therapy and cigarette smoking -- that the researchers found impacted the look of a woman's breasts. While we all have much more to worry about than how our breasts look, it's nice to know some of the things we may already do, like moisturizing regularly, actually make a difference.

LOOK: 4 Factors That May Impact How Your Breasts Look

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  • Breast Cancer

    Unsurprisingly, the study found that a history of breast cancer has a significant impact on how a woman's breasts look later in life. Breast cancer impacts breasts in three ways: 1. Women with breast cancer have more scarring on their breasts than women who never had breast cancer. 2. Cancer survivors have greater <a href="http://en.wikipedia.org/wiki/Ptosis_(breasts)" target="_hplink">glandular ptosis</a>, otherwise known as drooping or saggy breasts. 3. Women who survived breast cancer are also more likely to have asymmetrical breasts.

  • Cigarette Smoking

    Smoking cigarettes also negatively impacts women's breasts over time, the study showed. Cigarettes decrease breasts' skin quality, breast projection (meaning the distance that one's breasts extend forward from the chest). Women who smoked cigarettes were also found to have less attractive breast size and less attractive areolar size (the skin surrounding the nipple).

  • Hormone Replacement Therapy

    Hormone replacement therapy (HRT), a treatment generally used to decrease the symptoms of menopause, was found to have positive effects on breast attractiveness. Not only did women who went through HRT have breasts that looked younger than those that didn't undergo the treatment, but they also had more attractive breast size, shape and areolas. Women who underwent HRT were also found to have better breast projection (perkiness) and fewer patches of darkened skin on their breasts. This apparent benefit of HRT notwithstanding, researchers and physicians continue to <a href="http://www.myhealthnewsdaily.com/1227-5-experts-hormone-replacement-therapy-safe.html" target="_hplink">debate the safety of HRT</a>. Studies have found that some kinds of HRT may increase <a href="http://www.myhealthnewsdaily.com/485-hormone-therapy-increases-ovarian-cancer-risk.html" target="_hplink">risk of ovarian cancer</a> and <a href="http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/MedicalTreatments/menopausal-hormone-replacement-therapy-and-cancer-risk" target="_hplink">breast cancer</a>, while other types of HRT may <a href="http://www.myhealthnewsdaily.com/645-estrogen-hormone-replacement-therapy-reduces-breast-cancer.html" target="_hplink">decrease risk of certain cancers.</a>

  • Daily Moisturizing

    Women who moisturized their skin daily were found to have significantly fewer wrinkles on their breasts than those who did not. Moisturizing was also associated with fewer stretch marks and dark patches on the skin. (Anyone else reaching for their bottle of moisturizer right now?)

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