An article published this week in the prestigious journal Nature Medicine documents what is believed to be the first evidence that Alzheimer’s disease can be transmitted from person to person.

The finding arose from long-term follow up of patients who received human growth hormone (hGH) that was taken from brain tissue of deceased donors.

Preparations of donated hGH were used in medicine to treat a variety of conditions from 1959 onwards – including in Australia from the mid 60s.

The practice stopped in 1985 when it was discovered around 200 patients worldwide who had received these donations went on to develop Creuztfeldt-Jakob disease (CJD), which causes a rapidly progressive dementia. This is an otherwise extremely rare condition, affecting roughly one person in a million.

What’s CJD got to do with Alzehimer’s?

CJD is caused by prions: infective particles that are neither bacterial or viral, but consist of abnormally folded proteins that can be transmitted from cell to cell.

Other prion diseases include kuru, a dementia seen in New Guinea tribespeople caused by eating human tissue, scrapie (a disease of sheep) and variant CJD or bovine spongiform encephalopathy, otherwise known as mad cow disease. This raised public health concerns over the eating of beef products in the United Kingdom in the 1980s.

Human growth hormone used to come from donated organs

Human growth hormone (hGH) is produced in the brain by the pituitary gland. Treatments were originally prepared from purified human pituitary tissue.

But because the amount of hGH contained in a single gland is extremely small, any single dose given to any one patient could contain material from around 16,000 donated glands.

An average course of hGH treatment lasts around four years, so the chances of receiving contaminated material – even for a very rare condition such as CJD – became quite high for such people.

hGH is now manufactured synthetically in a laboratory, rather than from human tissue. So this particular mode of CJD transmission is no longer a risk.

What are the latest findings about Alzheimer’s disease?

The Nature Medicine paper provides the first evidence that transmission of Alzheimer’s disease can occur via human-to-human transmission.

The authors examined the outcomes of people who received donated hGH until 1985. They found five such recipients had developed early-onset Alzheimer’s disease.

They considered other explanations for the findings but concluded donated hGH was the likely cause.

Given Alzheimer’s disease is a much more common illness than CJD, the authors presume those who received donated hGH before 1985 may be at higher risk of developing Alzheimer’s disease.

Alzheimer’s disease is caused by presence of two abnormally folded proteins: amyloid and tau. There is increasing evidence these proteins spread in the brain in a similar way to prion diseases. So the mode of transmission the authors propose is certainly plausible.

However, given the amyloid protein deposits in the brain at least 20 years before clinical Alzheimer’s disease develops, there is likely to be a considerable time lag before cases that might arise from the receipt of donated hGH become evident.

When was this process used in Australia?

In Australia, donated pituitary material was used from 1967 to 1985 to treat people with short stature and infertility.

More than 2,000 people received such treatment. Four developed CJD, the last case identified in 1991. All four cases were likely linked to a single contaminated batch.

The risks of any other cases of CJD developing now in pituitary material recipients, so long after the occurrence of the last identified case in Australia, are considered to be incredibly small.

Early-onset Alzheimer’s disease (defined as occurring before the age of 65) is uncommon, accounting for around 5% of all cases. Below the age of 50 it’s rare and likely to have a genetic contribution.

The risk is very low – and you can’t ‘catch’ it like a virus

The Nature Medicine paper identified five cases which were diagnosed in people aged 38 to 55. This is more than could be expected by chance, but still very low in comparison to the total number of patients treated worldwide.

Although the long “incubation period” of Alzheimer’s disease may mean more similar cases may be identified in the future, the absolute risk remains very low. The main scientific interest of the article lies in the fact it’s first to demonstrate that Alzheimer’s disease can be transmitted from person to person in a similar way to prion diseases, rather than in any public health risk.

The authors were keen to emphasise, as I will, that Alzheimer’s cannot be contracted via contact with or providing care to people with Alzheimer’s disease.

Steve Macfarlane, Head of Clinical Services, Dementia Support Australia, & Associate Professor of Psychiatry, Monash University

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

We know the importance of staying hydrated, especially in hot weather. But even for something as simple as a drink of water, conflicting advice and urban myths abound.

Is cold water really bad for your health? What about hot water from the tap? And what is “raw water”? Let’s dive in and find out.

Myth 1: Cold water is bad for you

Some recent TikToks have suggested cold water causes health problems by somehow “contracting blood vessels” and “restricting digestion”. There is little evidence for this.

While a 2001 study found 51 out of 669 women tested (7.6%) got a headache after drinking cold water, most of them already suffered from migraines and the work hasn’t been repeated since.

Cold drinks were shown to cause discomfort in people with achalasia (a rare swallowing disorder) in 2012 but the study only had 12 participants.

For most people, the temperature you drink your water is down to personal preference and circumstances. Cold water after exercise in summer or hot water to relax in winter won’t make any difference to your overall health.

Myth 2: You shouldn’t drink hot tap water

This belief has a grain of scientific truth behind it. Hot water is generally a better solvent than cold water, so may dissolve metals and minerals from pipes better. Hot water is also often stored in tanks and may be heated and cooled many times. Bacteria and other disease-causing microorganisms tend to grow better in warm water and can build up over time.

It’s better to fill your cup from the cold tap and get hot water for drinks from the kettle.

Myth 3: Bottled water is better

While bottled water might be safer in certain parts of the world due to pollution of source water, there is no real advantage to drinking bottled water in Australia and similar countries.

According to University of Queensland researchers, bottled water is not safer than tap water. It may even be tap water. Most people can’t tell the difference either. Bottled water usually costs (substantially) more than turning on the tap and is worse for the environment.

What about lead in tap water? This problem hit the headlines after a public health emergency in Flint, Michigan, in the United States. But Flint used lead pipes with a corrosion inhibitor (in this case orthophosphate) to keep lead from dissolving. Then the city switched water sources to one without a corrosion inhibitor. Lead levels rose and a public emergency was declared.

Fortunately, lead pipes haven’t been used in Australia since the 1930s. While lead might be present in some old plumbing products, it is unlikely to cause problems.

Myth 4: Raw water is naturally healthier

Some people bypass bottled and tap water, going straight to the source.

The “raw water” trend emerged a few years ago, encouraging people to drink from rivers, streams and lakes. There is even a website to help you find a local source.

Supporters say our ancestors drank spring water, so we should, too. However, our ancestors also often died from dysentery and cholera and their life expectancy was low.

While it is true even highly treated drinking water can contain low levels of things like microplastics, unless you live somewhere very remote, the risks of drinking untreated water are far higher as it is more likely to contain pollutants from the surrounding area.

Myth 5: It’s OK to drink directly from hoses

Tempting as it may be, it’s probably best not to drink from the hose when watering the plants. Water might have sat in there, in the warm sun for weeks or more potentially leading to bacterial buildup.

Similarly, while drinking water fountains are generally perfectly safe to use, they can contain a variety of bacteria. It’s useful (though not essential) to run them for a few seconds before you start to drink so as to get fresh water through the system rather than what might have been sat there for a while.

We are fortunate to be able to take safe drinking water for granted. Billions of people around the world are not so lucky.

So whether you like it hot or cold, or somewhere in between, feel free to enjoy a glass of water this summer.

Just don’t drink it from the hose.

Oliver A.H. Jones, Professor of chemistry, RMIT University

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