ANTIAGEING_AF2 - page 10

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Monographic special issue:
ANTI-AGEING & BEAUTY INSIDE
-
Agro FOOD Industry Hi Tech
- vol. 28(2) - March/April 2017
KEYWORDS: Elderly, ageing, odour, smell, olfaction.
Abstract
Several authors argued that ageing is accompanied by an impairment of olfactory abilities,
i.e.
, the ability
to perceive an odour or a taste. However, beyond this overall effect of age on chemosensory abilities,
ageing is accompanied by variability in olfactory performance: the decline of odour perception with age is not uniform across odorants
neither across elderly individuals. Decline in odour perception may not be inevitable to the aging individual and that factors secondary
to aging, such as poor health status or cognitive decline, may contribute to deficits in odour detectability beyond the age effect
per se
.
Smelling in the old age
« Sense of smell? I never gave it a thought. You don’t normally
give it a thought. But when I lost it – it was like being struck blind.
Life lost a good deal of its savour – one doesn’t realise how
much “savour” is smell. You smell people, you smell books, you
smell the city, you smell the spring – maybe not consciously, but
as a rich unconscious background to everything else. My whole
world was suddenly radically poorer… » (Oliver Sacks, The Man
who Mistook his Wife for a Hat) (1)
In 1984, Richard Doty and his colleagues (2) asked 1,955 persons
ranging in age from 5 to 99 years to complete a “scratch ‘n sniff”
olfactory test. This test consisted of 40 different “scratch and
sniff” strips which were embedded with a microencapsulated
odorant. After each scent was released, the respondent smelled
and identified the odour from four choices. Results revealed that
peak performance occurs in the third through fifth decades of
life (between 20 and 50 years) and declined markedly after the
seventh (2). In line with this huge survey, several authors claimed
that our olfactory sense decline as we grow old (3,4). Actually,
elderly people believe that they have loss in smell acuity – as well
as they have loss in vision or hearing acuity.
However, are we really meant to no longer feel the “savour of
life” when we grow old, as it is described in Oliver Sacks’s book?
The very first researches such as the one of Doty and colleagues
used an identification task to assess the impact of ageing on
olfactory abilities. However, identifying an odour by its true name is
a reputedly difficult task, even for young people (5). Learning odour
names occurs haphazardly in the course of olfactory experience,
throughout life course, leading to a limited and often idiosyncratic
vocabulary to name odour (on the opposite, there is a strong social
pressure early in childhood to identify objects, colours or even sounds
by consensual names). Consequently, the use of identification tests
could lead to an overestimation of the age-related decline in ability
to detect odorous stimuli: an older individual may fail to find the
expected name of an odour not because he is unable to perceive it
but rather because he is unable to recall its name (6).
Furthermore, several authors argued that the overall effect of
age on olfaction hides a large variability in olfactory acuity
(6-9). In 1989, Wysocki and Gilbert (10) run a very large survey to
demonstrate that “the world does not necessarily become less
fragrant as we age”. Following the publication of an article about
olfaction in the National Geographic, they sent a smell test to all
10.5 million members of the Society. Surveys were returned by 1.42
million readers and the authors analysed the data from a random
sub-sample of 26,200 US readers aged from 10 to more than 90
years old. The olfactory test consisted in six microencapsulated
odorants, corresponding to the following odours: banana, clove,
natural gas (i.e. mercaptan added to natural gas a waring agent),
musk, rose, urine. After each scent was released, the respondent
was asked (among others) whether he smelled something or not
and to rate the intensity of the odour. Interestingly, results showed
that the decline of odour perception with age was not uniform
across odorants. For instance, large changes were noted in the
ability to smell androstenone (musk/urine odour) but the likelihood
of smelling rose was quite high, at least until the eighth or ninth
decade. Surprisingly, many people, even those in midlife years
failed to detect mercaptan, the warning agent in natural gas.
In a recent survey, we evaluated the chemosensory abilities
of 559 subjects, aged from 65 to 99 years (11). Specifically,
we assessed the ability of respondents to detect odours at a
low and medium intensity, the ability to discriminate between
different odour qualities (for instance, between the odour of
garlic and the odour of onions or between the odour of beef
and the odour of fish), the ability to recognize an odour as a
food odour or not, and the ability to perceived the salty taste
in water solution. Data were submitted to a clustering analysis
to highlight clusters of respondents displaying similar patterns
of performances. In fact, the results revealed that 43% of the
sample presented well-preserved olfactory and gustatory
abilities, whereas 21% of the participants presented a moderate
impairment. Of the sample, 33% presented well-preserved
olfactory abilities but strong impairment in gustatory abilities and
only 3% were nearly anosmic. These results clearly demonstrate
CLAIRE SULMONT-ROSSÉ
Centre des Sciences du Goût et de l’Alimentation
AgroSup Dijon, CNRS, INRA, Univ. Bourgogne Franche-Comté,
Dijon, France
Claire Sulmont-Rossé
ANTI-AGEING & BEAUTY INSIDE
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