A recent study has suggested Shingrix, a relatively new vaccine given to protect older adults against shingles, may delay the onset of dementia.

This might seem like a bizarre link, but actually, research has previously shown an older version of the shingles vaccine, Zostavax, reduced the risk of dementia.

In this new study, published last week in the journal Nature Medicine, researchers from the United Kingdom found Shingrix delayed dementia onset by 17% compared with Zostavax.

So how did the researchers work this out, and how could a shingles vaccine affect dementia risk?

From Zostavax to Shingrix

Shingles is a viral infection caused by the varicella-zoster virus. It causes painful rashes, and affects older people in particular.

Previously, Zostavax was used to vaccinate against shingles. It was administered as a single shot and provided good protection for about five years.

Shingrix has been developed based on a newer vaccine technology, and is thought to offer stronger and longer-lasting protection. Given in two doses, it’s now the preferred option for shingles vaccination in Australia and elsewhere.

In November 2023, Shingrix replaced Zostavax on the National Immunisation Program, making it available for free to those at highest risk of complications from shingles. This includes all adults aged 65 and over, First Nations people aged 50 and older, and younger adults with certain medical conditions that affect their immune systems.

What the study found

Shingrix was approved by the US Food and Drugs Administration in October 2017. The researchers in the new study used the transition from Zostavax to Shingrix in the United States as an opportunity for research.

They selected 103,837 people who received Zostavax (between October 2014 and September 2017) and compared them with 103,837 people who received Shingrix (between November 2017 and October 2020).

By analysing data from electronic health records, they found people who received Shingrix had a 17% increase in “diagnosis-free time” during the follow-up period (up to six years after vaccination) compared with those who received Zostavax. This was equivalent to an average of 164 extra days without a dementia diagnosis.

The researchers also compared the shingles vaccines to other vaccines: influenza, and a combined vaccine for tetanus, diphtheria and pertussis. Shingrix and Zostavax performed around 14–27% better in lowering the risk of a dementia diagnosis, with Shingrix associated with a greater improvement.

The benefits of Shingrix in terms of dementia risk were significant for both sexes, but more pronounced for women. This is not entirely surprising, because we know women have a higher risk of developing dementia due to interplay of biological factors. These include being more sensitive to certain genetic mutations associated with dementia and hormonal differences.

Why the link?

The idea that vaccination against viral infection can lower the risk of dementia has been around for more than two decades. Associations have been observed between vaccines, such as those for diphtheria, tetanus, polio and influenza, and subsequent dementia risk.

Research has shown Zostavax vaccination can reduce the risk of developing dementia by 20% compared with people who are unvaccinated.

But it may not be that the vaccines themselves protect against dementia. Rather, it may be the resulting lack of viral infection creating this effect. Research indicates bacterial infections in the gut, as well as viral infections, are associated with a higher risk of dementia.

Notably, untreated infections with herpes simplex (herpes) virus – closely related to the varicella-zoster virus that causes shingles – can significantly increase the risk of developing dementia. Research has also shown shingles increases the risk of a later dementia diagnosis.

The mechanism is not entirely clear. But there are two potential pathways which may help us understand why infections could increase the risk of dementia.

First, certain molecules are produced when a baby is developing in the womb to help with the body’s development. These molecules have the potential to cause inflammation and accelerate ageing, so the production of these molecules is silenced around birth. However, viral infections such as shingles can reactivate the production of these molecules in adult life which could hypothetically lead to dementia.

Second, in Alzheimer’s disease, a specific protein called Amyloid-β go rogue and kill brain cells. Certain proteins produced by viruses such as COVID and bad gut bacteria have the potential to support Amyloid-β in its toxic form. In laboratory conditions, these proteins have been shown to accelerate the onset of dementia.

What does this all mean?

With an ageing population, the burden of dementia is only likely to become greater in the years to come. There’s a lot more we have to learn about the causes of the disease and what we can potentially do to prevent and treat it.

This new study has some limitations. For example, time without a diagnosis doesn’t necessarily mean time without disease. Some people may have underlying disease with delayed diagnosis.

This research indicates Shingrix could have a silent benefit, but it’s too early to suggest we can use antiviral vaccines to prevent dementia.

Overall, we need more research exploring in greater detail how infections are linked with dementia. This will help us understand the root causes of dementia and design potential therapies.

Ibrahim Javed, Enterprise and NHMRC Emerging Leadership Fellow, UniSA Clinical & Health Sciences, University of South Australia

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

Many people are drinking less sugary soft drink than in the past. This is a great win for public health, given the recognised risks of diets high in sugar-sweetened drinks.

But over time, intake of diet soft drinks has grown. In fact, it’s so high that these products are now regularly detected in wastewater.

So what does the research say about how your health is affected in the long term if you drink them often?

What makes diet soft drinks sweet?

The World Health Organization (WHO) advises people “reduce their daily intake of free sugars to less than 10% of their total energy intake. A further reduction to below 5% or roughly 25 grams (six teaspoons) per day would provide additional health benefits.”

But most regular soft drinks contain a lot of sugar. A regular 335 millilitre can of original Coca-Cola contains at least seven teaspoons of added sugar.

Diet soft drinks are designed to taste similar to regular soft drinks but without the sugar. Instead of sugar, diet soft drinks contain artificial or natural sweeteners. The artificial sweeteners include aspartame, saccharin and sucralose. The natural sweeteners include stevia and monk fruit extract, which come from plant sources.

Many artificial sweeteners are much sweeter than sugar so less is needed to provide the same burst of sweetness.

Diet soft drinks are marketed as healthier alternatives to regular soft drinks, particularly for people who want to reduce their sugar intake or manage their weight.

But while surveys of Australian adults and adolescents show most people understand the benefits of reducing their sugar intake, they often aren’t as aware about how diet drinks may affect health more broadly.

What does the research say about aspartame?

The artificial sweeteners in soft drinks are considered safe for consumption by food authorities, including in the US and Australia. However, some researchers have raised concern about the long-term risks of consumption.

People who drink diet soft drinks regularly and often are more likely to develop certain metabolic conditions (such as diabetes and heart disease) than those who don’t drink diet soft drinks.

The link was found even after accounting for other dietary and lifestyle factors (such as physical activity).

In 2023, the WHO announced reports had found aspartame – the main sweetener used in diet soft drinks – was “possibly carcinogenic to humans” (carcinogenic means cancer-causing).

Importantly though, the report noted there is not enough current scientific evidence to be truly confident aspartame may increase the risk of cancer and emphasised it’s safe to consume occasionally.

Will diet soft drinks help manage weight?

Despite the word “diet” in the name, diet soft drinks are not strongly linked with weight management.

In 2022, the WHO conducted a systematic review (where researchers look at all available evidence on a topic) on whether the use of artificial sweeteners is beneficial for weight management.

Overall, the randomised controlled trials they looked at suggested slightly more weight loss in people who used artificial sweeteners.

But the observational studies (where no intervention occurs and participants are monitored over time) found people who consume high amounts of artificial sweeteners tended to have an increased risk of higher body mass index and a 76% increased likelihood of having obesity.

In other words, artificial sweeteners may not directly help manage weight over the long term. This resulted in the WHO advising artificial sweeteners should not be used to manage weight.

Studies in animals have suggested consuming high levels of artificial sweeteners can signal to the brain it is being starved of fuel, which can lead to more eating. However, the evidence for this happening in humans is still unproven.

What about inflammation and dental issues?

There is some early evidence artificial sweeteners may irritate the lining of the digestive system, causing inflammation and increasing the likelihood of diarrhoea, constipation, bloating and other symptoms often associated with irritable bowel syndrome. However, this study noted more research is needed.

High amounts of diet soft drinks have also been linked with liver disease, which is based on inflammation.

The consumption of diet soft drinks is also associated with dental erosion.

Many soft drinks contain phosphoric and citric acid, which can damage your tooth enamel and contribute to dental erosion.

Moderation is key

As with many aspects of nutrition, moderation is key with diet soft drinks.

Drinking diet soft drinks occasionally is unlikely to harm your health, but frequent or excessive intake may increase health risks in the longer term.

Plain water, infused water, sparkling water, herbal teas or milks remain the best options for hydration.

Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland and Emily Burch, Accredited Practising Dietitian and Lecturer, Southern Cross University

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