Many women worry hormonal contraceptives have dangerous side-effects including increased cancer risk. But this perception is often out of proportion with the actual risks.

So, what does the research actually say about cancer risk for contraceptive users?

And is your cancer risk different if, instead of the pill, you use long-acting reversible contraceptives? These include intrauterine devices or IUDs (such as Mirena), implants under the skin (such as Implanon), and injections (such as Depo Provera).

Our new study, conducted by the University of Queensland and QIMR Berghofer Medical Research Institute and published by the Journal of the National Cancer Institute, looked at this question.

We found long-acting contraceptives seem to be as safe as the pill when it comes to cancer risk (which is good news) but not necessarily any safer than the pill.

How does the contraceptive pill affect cancer risk?

The International Agency for Research on Cancer, which compiles evidence on cancer causes, has concluded that oral contraceptives have mixed effects on cancer risk.

Using the oral contraceptive pill:

• slightly increases your risk of breast and cervical cancer in the short term, but
• substantially reduces your risk of cancers of the uterus and ovaries in the longer term.

Our earlier work showed the pill was responsible for preventing far more cancers overall than it contributed to.

In previous research we estimated that in 2010, oral contraceptive pill use prevented over 1,300 cases of endometrial and ovarian cancers in Australian women.

It also prevented almost 500 deaths from these cancers in 2013. This is a reduction of around 25% in the deaths that could have occurred that year if women hadn’t taken the pill.

In contrast, we calculated the pill may have contributed to around 15 deaths from breast cancer in 2013, which is less than 0.5% of all breast cancer deaths in that year.

What about long-acting reversible contraceptives and cancer risk?

Long-acting reversible contraceptives – which include intrauterine devices or IUDs, implants under the skin, and injections – release progesterone-like hormones.

These are very effective contraceptives that can last from a few months (injections) up to seven years (intrauterine devices).

Notably, they don’t contain the hormone oestrogen, which may be responsible for some of the side-effects of the pill (including perhaps contributing to a higher risk of breast cancer).

Use of these long-acting contraceptives has doubled over the past decade, while the use of the pill has declined. So it’s important to know whether this change could affect cancer risk for Australian women.

Our new study of more than 1 million Australian women investigated whether long-acting, reversible contraceptives affect risk of invasive cancers. We compared the results to the oral contraceptive pill.

We used de-identified health records for Australian women aged 55 and under in 2002.

Among this group, about 176,000 were diagnosed with cancer between 2004 and 2013 when the oldest women were aged 67. We compared hormonal contraceptive use among these women who got cancer to women without cancer.

We found that long-term users of all types of hormonal contraception had around a 70% lower risk of developing endometrial cancer in the years after use. In other words, the risk of developing endometrial cancer is substantially lower among women who took hormonal contraception compared to those who didn’t.

For ovarian cancer, we saw a 50% reduced risk (compared to those who took no hormonal contraception) for women who were long-term users of the hormone-containing IUD.

The risk reduction was not as marked for the implants or injections, however few long-term users of these products developed these cancers in our study.

As the risk of endometrial and ovarian cancers increases with age, it will be important to look at cancer risk in these women as they get older.

What about breast cancer risk?

Our findings suggest that the risk of breast cancer for current users of long-acting contraceptives is similar to users of the pill.

However, the contraceptive injection was only associated with an increase in breast cancer risk after five years of use and there was no longer a higher risk once women stopped using them.

Our results suggested that the risk of breast cancer also reduces after stopping use of the contraceptive implants.

We will need to follow-up the women for longer to determine whether this is also the case for the IUD.

It is worth emphasising that the breast cancer risk associated with all hormonal contraceptives is very small.

About 30 in every 100,000 women aged 20 to 39 years develop breast cancer each year, and any hormonal contraceptive use would only increase this to around 36 cases per 100,000.

What about other cancers?

Our study did not show any consistent relationships between contraceptive use and other cancers types. However, we only at looked at invasive cancers (meaning those that start at a primary site but have the potential to spread to other parts of the body).

A recent French study found that prolonged use of the contraceptive injection increased the risk of meningioma (a type of benign brain tumour).

However, meningiomas are rare, especially in young women. There are around two cases in every 100,000 in women aged 20–39, so the extra number of cases linked to contraceptive injection use was small.

The French study found the hormonal IUD did not increase meningioma risk (and they did not investigate contraceptive implants).

Benefits and side-effects

There are benefits and side-effects for all medicines, including contraceptives, but it is important to know most very serious side-effects are rare.

A conversation with your doctor about the balance of benefits and side-effects for you is always a good place to start.

Susan Jordan, Professor of Epidemiology, The University of Queensland; Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland, and Penny Webb, Distinguished Scientist, Gynaecological Cancers Group, QIMR Berghofer Medical Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

So, you got your eyesight tested and found out you need your first pair of glasses. Or you found out you need a stronger pair than the ones you have. You put them on and everything looks crystal clear. But after a few weeks things look blurrier without them than they did before your eye test. What’s going on?

Some people start to wear spectacles for the first time and perceive their vision is “bad” when they take their glasses off. They incorrectly interpret this as the glasses making their vision worse. Fear of this might make them less likely to wear their glasses.

But what they are noticing is how much better the world appears through the glasses. They become less tolerant of a blurry world when they remove them.

Here are some other things you might notice about eyesight and wearing glasses.

Lazy eyes?

Some people sense an increasing reliance on glasses and wonder if their eyes have become “lazy”.

Our eyes work in much the same way as an auto-focus camera. A flexible lens inside each eye is controlled by muscles that let us focus on objects in the distance (such as a footy scoreboard) by relaxing the muscle to flatten the lens. When the muscle contracts it makes the lens steeper and more powerful to see things that are much closer to us (such as a text message).

From the age of about 40, the lens in our eye progressively hardens and loses its ability to change shape. Gradually, we lose our capacity to focus on near objects. This is called “presbyopia” and at the moment there are no treatments for this lens hardening.

Optometrists correct this with prescription glasses that take the load of your natural lens. The lenses allow you to see those up-close images clearly by providing extra refractive power.

Once we are used to seeing clearly, our tolerance for blurry vision will be lower and we will reach for the glasses to see well again.

The wrong glasses?

Wearing old glasses, the wrong prescription (or even someone else’s glasses) won’t allow you to see as well as possible for day-to-day tasks. It could also cause eyestrain and headaches.

Incorrectly prescribed or dispensed prescription glasses can lead to vision impairment in children as their visual system is still in development.

But it is more common for kids to develop long-term vision problems as a result of not wearing glasses when they need them.

By the time children are about 10–12 years of age, wearing incorrect spectacles is less likely to cause their eyes to become lazy or damage vision in the long term, but it is likely to result in blurry or uncomfortable vision during daily wear.

Registered optometrists in Australia are trained to assess refractive error (whether the eye focuses light into the retina) as well as the different aspects of ocular function (including how the eyes work together, change focus, move around to see objects). All of these help us see clearly and comfortably.

What about dirty glasses?

Dirty or scratched glasses can give you the impression your vision is worse than it actually is. Just like a window, the dirtier your glasses are, the more difficult it is to see clearly through them. Cleaning glasses regularly with a microfibre lens cloth will help.

While dirty glasses are not commonly associated with eye infections, some research suggests dirty glasses can harbour bacteria with the remote but theoretical potential to cause eye infection.

To ensure best possible vision, people who wear prescription glasses every day should clean their lenses at least every morning and twice a day where required. Cleaning frames with alcohol wipes can reduce bacterial contamination by 96% – but care should be taken as alcohol can damage some frames, depending on what they are made of.

When should I get my eyes checked?

Regular eye exams, starting just before school age, are important for ocular health. Most prescriptions for corrective glasses expire within two years and contact lens prescriptions often expire after a year. So you’ll need an eye check for a new pair every year or so.

Kids with ocular conditions such as progressive myopia (short-sightedness), strabismus (poor eye alignment), or amblyopia (reduced vision in one eye) will need checks at least every year, but likely more often. Likewise, people over 65 or who have known eye conditions, such as glaucoma, will be recommended more frequent checks.

An online prescription estimator is no substitute for a full eye examination. If you have a valid prescription then you can order glasses online, but you miss out on the ability to check the fit of the frame or to have them adjusted properly. This is particularly important for multifocal lenses where even a millimetre or two of misalignment can cause uncomfortable or blurry vision.

Conditions such as diabetes or high blood pressure, can affect the eyes so regular eye checks can also help flag broader health issues. The vast majority of eye conditions can be treated if caught early, highlighting the importance of regular preventative care.

James Andrew Armitage, Professor of Optometry and Course Director, Deakin University and Nick Hockley, Lecturer in Optometric Clinical Skills, Director Deakin Collaborative Eye Care Clinic, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.