Daily aspirin therapy: Is it for everyone?

Previously, it has been widely accepted that taking low dose aspirin every day can lower the risk of heart attack and stroke.

Is it time to revisit this?

Is this advice for everyone and are there any risks with this?

Aspirin for preventative use has been indicated in two main areas – vascular disease thought to reduce the risk of heart attack and stroke and cancer, thought to primarily have a role in reducing the risk of colorectal or bowel cancer but possibly other cancers.

Let’s discuss vascular disease first.

For this, aspirin can be used in 2 ways

The first way is primary prevention

• Primary prevention is for someone who has never had a heart attack or stroke

• They have not had coronary artery bypass surgery or a stent placement.

• They have not had blocked arteries in the legs, heart or other parts of the body.

• They would be taking aspirin to prevent these things from occurring

The second way is secondary prevention

• Secondary prevention is when someone takes low dose daily aspirin to reduce their risk of having ANOTHER heart attack or stroke meaning that they have already got heart disease or blocked arteries.

Low dose aspirin is 75 - 100mg and is available over the counter. Its use in secondary prevention is well established and there is a lot of supportive evidence from randomized control trials. It is highly recommended as long as it is monitored by a medical team and all your doctors are well aware you are using it.

Primary prevention is much more controversial and is not universally recommended for everyone. There are a few important things to know about aspirin.

Firstly, just because aspirin is available over the counter, this does not mean that long term daily use even at a low dose is safe for everyone. There are serious side effects and contraindications which may far outweigh potential benefits for many people.

Secondly, even at a low dose, if it is intended for long term use, all doctors in your treating team but especially your General Practitioner (GP) need to be aware you are taking it and ideally the decision to take it regularly should be discussed with your GP.

Thirdly, an Australian led study in 2018 from Monash University in Melbourne resulted in a recommendation being made by the Australian Heart Foundation that if Australians over the age of 70 years have no medical reason for taking daily low dose aspirin or they have not been advised to by their doctor then they should not be taking it. Australians over the age of 45 years of age would be better to see their GP or cardiologist for a cardiovascular health assessment before committing to long term aspirin use. There was no significant protective effect found for stroke or impact on mortality.

However, using aspirin intermittently for joint pain or a headache is absolutely OK.

The reason for these recommendations is because of potential side effects from long-term aspirin use. These include but are not limited to:

• Bleeding – this can be catastrophic. E.g. if someone falls over and hits their head and bleeds into their brain or if they have a ruptured stomach ulcer. It can also be magnified if people are taking blood thinners for other reasons such as warfarin.

• Anaemia or low blood iron levels– usually from slow gastrointestinal bleeding.

• Stomach ulcers from gastric irritation.

So, what about using aspirin to reduce the risk of cancer?

In 2023, Australian guidelines came out stating that all Australians aged 50–70 years, without a contraindication to aspirin, consider taking low dose aspirin (100–300mg) daily for 2.5 – 5 years to reduce the risk of bowel cancer. Studies indicate that whilst evidence is highest for low dose aspirin reducing the risk of bowel cancer (proximal colon in particular), there may be reduced risks for other cancers too. More research is needed for this though. There is no evidence that taking aspirin for longer than 5 years is associated with a higher risk reduction and in fact, taking aspirin for 2.5 years is likely just as effective as taking it for 5 years.

Contraindications to aspirin include

• Stomach ulcers

• Previous gastrointestinal bleeding

• Liver cirrhosis or liver disease

• Kidney disease

• Hypertension or high blood pressure

• Concomitant use of blood thinner medication

• Concomitant use of antihypertensive medication

• Heavy alcohol use

So, what is the take home message?

We do not recommend long term low dose aspirin therapy for primary prevention of cardiovascular disease and stroke.

We do recommend low dose aspirin if you are at high risk of vascular disease or if you have heart disease, vascular disease or have had a heart attack or stroke.

We do recommend 2.5 years of low dose aspirin therapy to reduce the risk of bowel cancer between the ages of 50–70 years as long as you do not have any contraindications to aspirin itself.

References

1. Daily Aspirin Therapy: Understand the Risks and Benefits: MAYO Clinic: (https://www.mayoclinic.org/diseases-conditions/heart-disease/in-depth/daily-aspirin-therapy/art-20046797 )[12/12/2024].

2. McNeil, J et al. Effect of Aspirin on All-Cause Mortality in the Health Elderly, The New England Journal of Medicine; Sept 2018 VOL 379: No 16 (https://www.nejm.org/doi/full/10.1056/NEJMoa1803955 ) [13/12/2024].

3. Daily low-dose aspirin has little impact on stroke risk and spikes risk of brain bleeding from falls: National Institute of Aging: November 2 2023 highlights (https://www.nia.nih.gov/news/daily-low-dose-aspirin-has-little-impact-stroke-risk-and-spikes-risk-brain-bleeding-falls ) [13/12/2024]

4. Onwuka, S. et al. Should I take aspirin? A qualitive study on the implementation of a decision aid on taking aspirin for bowel cancer prevention: Family Medicine Community Health Nov 2023 Nov 30: 11 (suppl 1).