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Being unable to identify scents predicts the risk of dying in the next five years more strongly than heart failure, cancer or lung disease, new research suggests.

Researchers asked 3,005 adults between 57 and 85 years of age to identify five odours: peppermint, fish, orange, rose and leather. Most were “normosmic”, with 46 and 29 per cent correctly identifying five and four odours respectively. Almost 20 per cent correctly identified two or three odours (hyposmia). The remainder were anosmic, correctly identifying one (2.4 per cent) or none (1.1 per cent). Olfactory performance declined steadily with age: 64 per cent of 57-year-olds correctly identified all five smells – a figure that declined to 25 per cent of 85-year-olds.

Over the next five years, 39 per cent of those with anosmia died, compared to 19 per cent and 10 per cent of those with hyposmia and normosmia respectively. Compared to people with normosmia, those with anosmia and hyposomia were 5.85 and 2.20-fold respectively more likely to die.

Impaired olfactory functions may indicate the body’s reduced ability to repair age-related damage, say the researchers. “Our findings could provide a useful clinical test; a quick and inexpensive way to identify patients most at risk.”