Supplementary Documentation for Perceived Age as a Biomarker of Ageing
Supplementary Material
Methods
Photography using the Fuji Digital Camera
Informed consent from the subjects was obtained for all the studies. The subjects in
all studies were in good health, were asked not to partake in vigorous exercise an hour before
their study visit, to refrain from alcohol use 24 hours before the visit, and were at rest for a
minimum of 15 minutes before the photography. All subjects wore a shawl to help give
consistent light illumination, were not wearing make-up and had had no cosmetic surgery.
Two Nikon flashes (SB80DX) were used for the English, Canadian and Spanish studies, a
Canfield twin flash was used for the Danish study, and two Sunpak Digit-flash 500 lamps
were used for the Chinese study. A Fuji S2 digital camera was used in all studies bar the
Chinese study where the Fuji S3 was utilised. The first photograph consisted of a frontal
facial shot (lower neck up) with the subject’s eyes closed, the second photograph was the
same as the first bar the subject’s eyes were open, and the third photograph consisted of a 45degree angle shot of the left side of the face with the eyes closed. A Macbeth colour chart
was present in the photographs for post photograph quality checking. A number of
photographs per subject were taken, and the best photograph for each type was selected by
the ‘correctness’ of subject presentation to the camera and consistent light illumination as
determined using the Macbeth colour chart.
Age Assessment Sessions
Images were presented with two questions via a web-site. The first question asked
assessors to choose an age group they though the subject looked like they belonged. The
choices consisted of 5 year age groups spanning the chronological age range of the subjects
Supplementary Documentation for Perceived Age as a Biomarker of Ageing
under study and approximately 5 years either side. Additionally, a choice was presented
which spanned any age greater than 5 years from the subject chronological age range (see
Figure 1 Supplementary Material). Due to the large age ranges the Chinese, Spanish and
Canadian studies were split into two groupings for the age assessments; 25-47 and 46-70 year
olds for the Chinese study, 30-57 and 48-70 years olds for the Spanish study and 28-42 and
52-68 for the Canadian study (Table 1).
The 18 subjects for each age assessment session were selected to be evenly distributed
across the chronological age range required for the session but were otherwise randomly
selected. The assessors typically carried out one age assessment session per day and each
image was assessed by almost all the assessors for each study bar the Spanish study where
each image was assessed by approximately half the assessors (also see Table 1). Each session
additionally contained three acclimatisation pictures (practice pictures) of study individuals
aged from the lowest, average and highest age from each study’s age range. The subjects that
made up the acclimatisation images were excluded from subsequent analysis. Subjects in all
assessment sessions were presented in a random order, except for the acclimatisation images
which were always presented as the first three images, albeit in a random order.
Although data on the ethnicity of the assessors was not collected, through recruitment
it was noted that the assessors were principally Caucasian for the European and Canadian
studies and East Asian for the Chinese study.
Statistical Analysis
When analysing the reproducibility of the perceived age scores, if an assessor
performed the study more than once, only the first instance was used. Sampling of the
assessor data was performed with replacement (i.e. the same assessor may be chosen more
than once in the same sample). The maximum age range (Table 2) is the maximum
Supplementary Documentation for Perceived Age as a Biomarker of Ageing
discrepancy that was found in the assessor sampling means given to an image. The
percentage that the inter-quartile range (of the sampled means) was of the median of the
sampled means for each image was also calculated. The mean interquartile percent (Table 2)
is the mean of these percentages across the images.
Table and Figures
Table 1: Percentage that each age option was chosen within the selected age group for each
study. There was a tendency for assessors to choose the middle age option of the 5 ages
available within the age group selected from the first question.
Canada (A) Canada (B) England
Spain
Denmark
China
Response within age group
Percent
Percent
Percent
Percent
Percent
Percent
1 Youngest age option
17.15
19.34
20.78
16.84
18.47
17.64
2 Second youngest age option
20.78
21.54
21.71
19.82
19.54
21.02
3 Middle age option
23.42
22.83
20.61
21.49
23.6
22.19
4 Second oldest age option
19.71
16.65
18.1
17.74
18
14.72
5 Oldest age option
18.94
19.64
18.81
24.12
20.39
24.43
Supplementary Documentation for Perceived Age as a Biomarker of Ageing
Figure 1: Example of an image presented to age assessors. Two questions were asked; first
the assessors were asked to select the age group to which the subject looked like they
belonged and then they were asked to choose an age with the selected age group.
Supplementary Documentation for Perceived Age as a Biomarker of Ageing
Figure 2: Examples of scatter graphs of age data. Correlations between chronological age
and perceived age for the English study (A, R=0.879, p-value <0.0001), between the Spanish
and British assessors on 10 English images (B, R=0.965, p-value <0.0001), between male and
female assessors on the Canadian images (C, R=0.996, p-value <0.0001) and between the
Danish nurses and the British assessors on the Danish twins (D, R=0.935, p-value<0.001).
The broken lines are the 1:1 regression line for the x and y axis scales, and the un-broken
lines are the regression lines for the y-axis data onto the x-axis data.