How Many of These 7 Cancer Risk Factors Apply to You?

Most of us treat cancer like a lottery ticket we never chose to buy. If the wrong number comes up, we assume there was nothing anyone could have done, and for a large share of cases, Canadian researchers have found that assumption is wrong.

The largest study of its kind in Canada found that about 4 in 10 cancer cases can be prevented through healthy living and policies that protect people's health. The handful of cancer risk factors behind most of those cases are habits you can change, and this guide walks through the seven that matter most. Count how many apply to you as you read, and keep that number handy, because there is a question for you partway down.

Key takeaways

The ComPARe study, funded by the Canadian Cancer Society, found that about 4 in 10 cancer cases in Canada can be prevented.

About 70,200 cancer cases in 2015 could have been prevented, and that number could reach 111,700 a year by 2042 if nothing changes.

Smoking was linked to about 32,700 cases in 2015, far more than any other preventable cause.

Too little physical activity, excess body weight, eating too little fruit, and sun exposure round out the top five.

Prevention lowers the chance that cancer starts, while screening catches it early, so you need both.

What does preventable actually mean?

Before the list, one point needs to be clear. Preventable does not mean that anyone's cancer is their fault, since plenty of people who never smoked and ate their vegetables still get sick. Genetics, age, and plain bad luck all play a part that no habit can erase.

What the research measures is odds. The Canadian Population Attributable Risk of Cancer study, known as ComPARe, looked at more than 30 types of cancer and more than 20 risk factors that people can change. Led by Dr. Christine Friedenreich of Alberta Health Services and the University of Calgary, the research team then estimated how many Canadian cases each factor explains. Each factor on this list tips the odds a little further toward illness, and removing it tips them back, though nothing in this list guarantees an outcome in either direction.

Why does smoking still top the list?

Smoking tobacco sits at the top of the list, which will surprise nobody. It remains the single largest preventable cause of cancer in Canada, linked to about 32,700 new cases in 2015 according to the study's detailed results. Most people think of the lungs first, though tobacco also raises the risk of cancers of the throat, mouth, bladder, and pancreas, among others.

The good news is that quitting pays off at any age, and your risk starts to fall once you stop. Pharmacists can walk you through nicotine replacement, and every province runs a free quit line. It is also why Health Canada keeps making its message harder to ignore, as our look at the new cigarette warning labels explains. Non-smokers have one related item to check as well. Radon, an invisible, radioactive gas that seeps into homes from the ground, is the number one cause of lung cancer in non-smokers, according to Health Canada. A home test kit is inexpensive, and if you have never tested, it is worth doing this winter while the windows are closed.

Smoking was linked to nearly three times as many preventable cases as the next biggest cause.

Is sitting most of the day really that risky?

Physical inactivity comes second on the ComPARe list, linked to about 11,600 new cases in 2015, which puts it ahead of factors that get far more attention. Researchers link long stretches of sitting to a higher risk of several cancers, including colorectal cancer, and the habit hides easily inside a desk job, a long commute, or a slower retirement routine.

The fix does not require a gym membership. Canada's 24-Hour Movement Guidelines recommend at least 150 minutes of moderate to vigorous activity a week, which works out to a brisk half-hour walk on five days, and the biggest gains come from going from nothing to something. A walk after dinner or a rule about taking phone calls on your feet counts for more than it feels like it does, and our guide to how many steps a day you actually need shows how little it takes to start.

How much does extra weight change your odds?

This finding made national headlines when the study came out. According to the Canadian Cancer Society, extra weight is on track to become the second leading preventable cause of cancer in Canada, behind only tobacco. Cases linked to excess weight could nearly triple by 2042, from 7,200 to 21,200 a year.

More than 1 in 2 Canadian adults carry excess weight, and the society links it to at least 13 types of cancer, including breast, colorectal, endometrial, and esophageal cancer. This is about gradual, lasting change, and a crash diet or a number on a scale misses the point. Even modest weight loss that you keep off shifts the odds, and the habits in the rest of this list happen to be the same ones that make it achievable.

If current trends hold, cases linked to excess weight would rise faster than any other preventable cause.

Does a nightly glass of wine count?

Alcohol is the risk factor most Canadians underestimate, partly because the message feels new. The Canadian Cancer Society says that regular drinking raises cancer risk even at low levels, and that the less you drink, the lower your risk. Alcohol is linked to cancers of the breast, colon, liver, mouth, and throat, among others.

Canada's Guidance on Alcohol and Health, released by the Canadian Centre on Substance Use and Addiction, puts low risk at two standard drinks a week or fewer. That is a long way from the old idea that a nightly glass of wine is good for you. You do not have to quit entirely to benefit, because cutting from daily drinks to weekend drinks, or from two glasses to one, moves your risk in the right direction. Our guide to how much alcohol is safe to drink in a week breaks down what counts as a standard drink.

Are you eating enough fruit and vegetables?

The surprise entry in the study's top five is eating too little fruit, which suggests the problem is less about what Canadians eat and more about what they skip. ComPARe linked low fruit intake to about 6,700 new cases in 2015, and diets light on fruit and vegetables, along with the fibre they bring, are tied to higher rates of several cancers.

The practical advice is simple and effective. Aim for fruit and vegetables at every meal, let half your plate be plants more often than not, and treat fibre-rich foods like beans, lentils, and whole grains as regulars instead of guests. Adding is easier than subtracting, and adding is what the evidence rewards here.

Do old sunburns still matter?

Sun exposure rounds out the top five preventable causes, linked to about 4,300 new cases in 2015, and skin cancer is among the most common cancers in Canada. The damage builds up over a lifetime, so the sunburns from decades ago still count, though it also means every summer you protect your skin from here on counts too. Sunscreen on exposed skin, a hat, shade during the strongest midday sun, and skipping tanning beds and trends like tanmaxxing cover most of it.

Knowing your own skin matters just as much. A mole that changes shape or colour, a spot that bleeds or will not heal, or anything new that stands out deserves a professional look. Our guide to the skin cancer signs that do not look like the pictures shows what to watch for.

Which infections can a vaccine prevent?

This one surprises almost everyone, because infections cause some cancers, and a vaccine can stop several of them. HPV, the human papillomavirus, causes nearly all cervical cancer along with several head, neck, and other cancers. The Canadian Cancer Society says cervical cancer is almost entirely preventable through HPV vaccination and screening. Research on vaccinated generations has been encouraging, as our report on what the HPV vaccine has done for young women explains.

Hepatitis B, which can lead to liver cancer, is also vaccine-preventable. School programs across Canada offer the HPV vaccine free, and adults who missed it can ask a doctor or pharmacist about catching up. Regular cervical screening still matters for anyone eligible, because vaccination and screening protect in different ways.

What if you counted four or more?

If you counted four or more, that is not a diagnosis, and it is not a verdict. Cancer risk factors stack the odds without deciding your future, and the whole point of the research is that this list can change. It works the other way too, since a score of zero is not immunity, which is why screening exists.

Screening programs run through each province at ages that vary across the country. Ontario, for example, now offers colorectal screening from age 45, and in most provinces you can book a mammogram yourself from age 40. It is worth knowing where you stand with each one instead of assuming someone will call when it is time.

Where should you start first?

Do not try to fix all seven by Friday. Pick the one that moves your personal odds the most and give it your attention first, and if you smoke, that one is always smoking. For everything else, small and permanent beats dramatic and temporary.

Choose one habit. Start with the factor that applies to you most strongly, since one lasting change beats seven abandoned ones.

Get support for quitting. Pharmacist-guided nicotine replacement and free provincial quit lines both improve your chances compared with going it alone.

Add before you subtract. One more walk, one more vegetable, and sunscreen by the door are easier to keep than a long list of rules.

Check your screening dates. Ask which provincial screening programs you are due for, including breast, cervical, and colorectal screening.

Book a checkup. Ask your doctor which of these factors matters most for you, given your age and family history.

For a wider view of everyday prevention, our guide to preventing heart disease, cancer, and more this year pulls the habits that protect several organs at once into one plan.

Frequently asked questions

Can you lower your risk if it runs in your family?

A family history raises your odds, though the habits in this guide still lower them. Tell your doctor which relatives were diagnosed and at what age, because a strong family history can mean starting screening earlier. Your doctor may also refer some families for genetic counselling to find out whether an inherited change is involved.

Does quitting smoking help if you have smoked for decades?

Quitting helps at any age, and your risk begins to fall once you stop, though it takes years to drop fully. Smoking is linked to more preventable cases in Canada than any other cause, so it is the single most valuable change a smoker can make. A pharmacist or a provincial quit line can help you build a plan.

How much activity do Canadian guidelines recommend?

Canadian guidelines recommend about 150 minutes of moderate activity a week for adults, such as a brisk 30-minute walk on five days. Any amount is better than none, and the biggest gains come from going from no activity to some. Breaking up long periods of sitting during the day also helps.

Is there a safe amount of alcohol?

The Canadian Cancer Society says that regular drinking raises cancer risk even at low levels, and the less you drink, the lower your risk. Canada's Guidance on Alcohol and Health puts low risk at two standard drinks a week or fewer. Cutting back still lowers your risk, even if you do not stop completely.

When should you start screening tests?

Screening ages depend on your province, your sex, and your family history. Most provinces now let people book a mammogram from age 40, and colorectal screening usually starts between 45 and 50. Cervical screening starts in your twenties in most provinces, so ask your doctor or provincial program which tests you are due for.

Do risk factors add up if you have several?

Cancer risk factors generally stack, so having several raises your odds more than having one. The good news works the same way, because each one you change lowers your overall risk. Talking through your list with a doctor helps you decide which change will make the biggest difference for you.

Your next step

The single most useful 15 minutes in prevention is a checkup where you ask which screenings you are due for and which of these factors matters most for you. The Medimap Health Hub has more on prevention and screening. You can also find a family practice that is taking new patients, or book a visit at a walk-in clinic near you this week.

Disclaimer: This article is for general information only and is not medical advice. It does not replace a conversation with a doctor or other qualified health professional who knows your history. If you think you are having a medical emergency, call 911 or go to the nearest emergency department.