Can Alzheimer's really be transmitted from person to person?

Alzheimer's disease could have the potential to spread from human to human through certain medical procedures, scientists have speculated.

Lead researcher Dr John Collinge and his team at University College London published a study which suggests that patients may have contracted the disease from contaminated growth hormones.

John Hardy, a leading Alzheimer's researcher at UCL described the findings as "potentially concerning" – so should we be alarmed?

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What did the scientists discover?

The study focused on eight people who died after contracting Creuzfeldt-Jakob disease (CJD) from a brain-derived human growth hormone (HGH) during the 1970s. Scientists found that seven of the eight people also had amyloid clusters – one of the proteins associated with Alzheimer's – despite their relatively young ages and lack of genetic variants associated with early-onset Alzheimer's, as well as their lack of family history of the disease. Researchers speculate that this may mean the protein "seeds" were also transmitted to them via the contaminated hormone injections and, in theory, could be transmitted by instruments used in surgery that are contaminated with infected brain material.

Does this mean you can "catch" the disease?

No. The study, though important, was extremely limited and inconclusive. "What we've found shouldn't be any cause for alarm," says Dr Collinge. "It's relevant to a very special and rare situation. It's telling us something about the underlying mechanisms of how these diseases might occur but we're not saying in any way Alzheimer's is an infectious disease. You can't 'catch' Alzheimer's."

The use of this specific growth hormone was discontinued in the 1980s once the risks were discovered. The NHS says there is no evidence the disease can be transmitted through any medical procedure. "I can reassure people that the NHS has extremely stringent procedures in place to minimise infection risk from surgical equipment, and patients are very well protected," says Chief Medical Officer Professor Dame Sally Davies.

What does their discovery mean?

"Perhaps research papers like this one should come with their own health warning: 'may cause unnecessary alarm'," says the BBC's health editor Michelle Roberts. "That's not to discredit their scientific worth; the findings are interesting and important for furthering understanding." Dr Collinge says the study could hint at a "paradigm shift" in the understanding of how a number of degenerative brain diseases work, but is calling for further research.