Vol. 25, No. 4
Printed In Great Britain
International Journal of Epidemiology
O International Epldemiological Association 1996
Validity and Reproducibility of
Alcohol Consumption in Italy
MONICA FERRARONI,* ADRIANO DECARLI,*" SILVIA FRANCESCHI,* CARLO LA VECCHIA,*-*
LUCILE ENARD,* EVA NEGRI,* MARIA PARPINELt AND SIMONETTA SALVINI*
Ferraroni M (Istltuto di Statistica Medica e Biometria, Universita degli Studi, Via Venezian 1, 20133 Milano, Italy),
Decarli A, Franceschi S, La Vecchia C, Enard L, Negri E, Parpinel M and Salvini S. Validity and reproducibility of alcohol
consumption In Italy. International Journal of Ep/dem/o/ogy 1996; 25: 775-782.
Background. The reproducibility and validity of alcohol consumption has not been adequately studied, particularly In
Mediterranean countries, where alcohol drinking Is a widespread habit, especially during meals.
Methods. We compared alcohol consumption measured by two interviewer-administered food frequency questionnaires
(FFQ) with average Intake derived from two 7-day dietary (7-DD) records (the reference method) on 395 volunteers.
Different types of alcoholic beverages were considered separately in order to verify the ability of the questionnaire to
assess detailed patterns of alcohol intake.
Results. A satisfactory level of reproducibility and validity of the pattern of alcohol consumption across different levels
and types of alcoholic beverage intake was observed. The reproducibility of wine and total alcohol intake showed
correlation coefficients >0.75 in both sexes. The validity was somewhat higher for wine (around 0.70) than for other
alcoholic beverages and total alcohol intake. This is probably accounted for by the more regular pattern of wine
consumption during the year as compared to other alcoholic beverages (beer, grappa, etc) which are more strongly
influenced by seasonal and daily variations. However, about 30% of abstainers according to FFQ were dnnkers by the
reference method. The opposite was observed in only 4% of subjects.
Conclusion. The FFQ Is a reliable and valid Instrument for collecting alcohol intake In regular drinkers. Lower validity in
irregular drinkers may be due to seasonal variation and/or inadequacy of the FFQ to capture irregular patterns of
consumption and/or Inadequacy of the average of two 7-DD as a reference method. Furthermore, a considerable degree
of misclassification was observed between non-drinkers and moderate dnnkers.
Keywords: alcohol consumption, dietary records, food frequency questionnaire, reproducibility, validity
Alcohol is an important determinant of several common
diseases in humans. Besides accidents and violence, alcohol drinking is strongly related to cancers of the upper
digestive and respiratory tracts, and may be moderately
associated with cancers of the breast and colon-rectum.
In contrast, moderate alcohol consumption appears
to be protective against cardiovascular diseases.1'2
While it has been commonly assumed that alcohol
drinking, and particularly heavy drinking, is underreported, the reproducibility and validity of the whole
range of alcohol consumption in various populations
has not been adequately studied. In a few studies based
on dietary questionnaires, total alcohol consumption
was considered among various other foods and/or
nutrients. 3 " 6 Only in the prospective studies of
American female nurses and male health professionals,
were the reproducibility and validity of alcohol consumption investigated ad hoc.1 High values of reproducibility were found, with Spearman correlation coefficients
of 0.92 for men and 0.90 for women. Diet records, used
as a reference method, were satisfactorily correlated
with a food frequency questionnaire (FFQ), particularly
with its replication (0.89 for men and 0.90 for women).
Pietinen et al.,3 in a study on reproducibility and validity of a self-administered FFQ, compared it with 12
2-day dietary records, distributed evenly over a period of 6 months. The reproducibility for total alcohol
intake, measured by intraclass correlation, was 0.88. In
the validation study, the de-attenuated Pearson coefficients ranged from 0.74 among alcohol users only
to 0.85 for all subjects. In the Netherlands, two studies were designed to test the reproducibility of FFQ
used in a population-based case-control study on diet
and pancreatic cancer. 4 The Pearson correlation
coefficients for total alcohol intake were 0.91 for the
first study and 0.87 for the second one. Posner et a/.,3
conducted a validation study within the Framingham
cohort investigation comparing nutrient intake by
* Istituto di Statistics Medica c Biometria, Universita degli Studi,
Via Venezian 1, 20133 Milano, Italy.
• • Istituto Nazionale per lo Studio e la Cure dei Tumori, Milano, Italy.
' Servizio di Epidemologia, Ceniro di Riferimento Oncologico, Aviano
(PN). Italy.
* Isiituto di Ricerche Farmacologiche 'Mario Negri', Milano, Italy.
1
Istituto Europeo di Oncologia, Divisione di Epidemiologia e
Biostatistica, Milano, Italy.
775
776
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
FFQ with 3-day food records. For total alcohol intake,
they reported a Spearman rank correlation coefficient
of 0.67 for males and 0.68 for females. In a Spanish
study restricted to women6 high values of Pearson
correlation coefficients were found: 0.88 was reported
for reproducibility, while values of 0.87 for a first FFQ
and 0.90 for a second one were shown for validity.
Alcohol drinking is a common habit in Italy, especially during meals, and particularly in males, although
this appears to have decreased over the last few years
and in younger generations.' In the present study we
compared alcohol consumption measured by two
interviewer-administered FFQ with average intake derived from two 7-day dietary (7-DD) records, used as
the reference method. This FFQ was designed for a
case-control study on the relation between nutritional
habits and cancer. Different types of alcoholic beverage
were considered separately in order to verify the ability
of the questionnaire to assess detailed patterns of
alcohol intake.
MATERIALS AND METHODS
Study Design
The general design of the present study has already
been described. 8 " 10 Briefly, volunteers from three
Italian provinces (Pordenone, Forll and Genoa) completed an interviewer-administered FFQ at the beginning of the study during autumn-winter 1990-1991.
Participants were also instructed to weigh and record
day-by-day in a diary all foods and beverages consumed during 7 consecutive days (7-DD records). The
7-DD records began in the days subsequent to the FFQ
administration, if possible on a Sunday. The same
scheme was proposed to the same subjects 3-10 months
later (6 months on the average), i.e. in spring-summer.
Participants were told they were taking part in a dietary
survey, but they were not aware of the study aims. Of
537 participants initially recruited, 452 (84%) completed the two FFQ and 395 (74%) completed the
two 7-DD records (130 males and 265 females, median age = 52, range = 35-69). The exclusion criteria
were defined in order to obtain as a reference an average intake taking into account the seasonal variation.
Consequently, 57 volunteers were not included in the
present validation study, 54 because they had only one
7-DD record and three because one of the 7-DD records
included fewer than 6 days of data collection.
The Food Frequency Questionnaire
The FFQ was developed to assess the total diet of subjects and, therefore, total energy intake, as well as
the intake of selected macro- and micro- nutrients. A
detailed description of this questionnaire has already
been given. 89 We obtained information on average
weekly frequency of consumption of single foods or
groups of foods, as well as complex recipes (including
the most common ones in the Italian diet) during the
previous year.
The FFQ included 77 foods, groups of foods or
recipes grouped into seven sections: (I) bread, cereals,
first courses; (2) second courses (i.e. meat and meat
substitutes); (3) side dishes (i.e. vegetables); (4) fruits;
(5) sweets, desserts and soft drinks, (6) milk, hot
beverages and sweeteners; (7) alcoholic beverages. The
FFQ looked more like the menu of a restaurant than
a shopping list. In particular, in the alcoholic beverage section, the daily number of drinks of wine (125
ml), beer (330 ml), grappa (30 ml), a common Italian
liquor, and other liquors (30 ml) was investigated.
The alcohol content per 100 g of beverage was
estimated, 10.45 g for wine, 2.8 g for beer, 33.6 g
for grappa and 34.6 g for other liquors, on the basis
of a food composition database specifically designed for the present study." l12 Daily intakes of alcohol
from different beverages were computed using the
number of days per week on which each type of
beverage was consumed and the average number of
drinks per day. The total alcohol consumption was
computed by adding the intakes of various alcoholic beverages. Small amounts of alcoholic beverages
added to food in the preparation of recipes were not
considered.
Seven-Day Dietary Record
In the diary used to fill in dietary information, different types of alcoholic beverage were recorded. For
each of these, information was elicited about type
and amount in grams. In the rare instances when the
information about the amount of alcohol was not
available, a standard amount (i.e. the same used in the
questionnaire) was assumed. The alcohol content was
evaluated for each alcoholic beverage" 1 2 and subsequently grouped into the four categories of alcoholic
beverages included in the FFQ (wine, beer, grappa,
other liquors). Alcohol added to recipes was not
considered.
Since 7-DD were considered for the analysis when at
least 6 consecutive days were recorded, the reference
mean daily intake was obtained for each volunteer
from 13 to 15 different estimates of daily consumption
(378 participants with two 7-DD, 10 with one 6-DD +
one 7-DD and seven with one 8-DD + one 7-DD).
For each subject, the reference mean daily intake was
obtained as the average of the two 7-DD records
ALCOHOL CONSUMPTION IN ITALY
(dietary record, DR). The DR were used as the reference method in this validation study.
Statistical Analysis
Means and standard deviations of alcohol intake derived from different alcoholic beverages were estimated
from each questionnaire as well as from the DR.
For the reproducibility study, paired t tests were
performed to compare the means of alcohol intake
estimated from the two questionnaires. Since the
distributions were skewed towards high values, alcohol values were logt (*+0.001) transformed, in order
to improve normality. Pearson product-moment correlation coefficients13 were used to assess both the
reproducibility of the questionnaire and the validity
with respect to the reference method. The Spearman rank correlations were also computed but, since
the results were similar, they are not presented.
We obtained different types of correlation coefficients: the first one (r,) after allowing for study
design variables, i.e. age, sex and centre, the second
one (rb) using energy-adjusted alcohol intakes from
both methods, by means of the regression of alcohol
intake on total energy intake, age, sex and centre. The
correlation was thus evaluated between the alcohol
component residuals (i.e. observed alcohol intake
minus intake predicted on the basis of energy intake
and the study design variables).14 Further, we evaluated
the de-attenuated unadjusted correlation coefficients
(rc) in order to take into account the inter-individual
variability of alcohol intake as given by the DR.15 For
the reproducibility study, the intraclass correlation (rd)
was also considered in order to measure the proportion
of total variation due to between-individual variability.13 We do not present P-values for correlation
coefficients because they have chiefly descriptive
purposes; however, with the available number of
participants, all r-values higher than 0.10 are significant
at 0.05 level.
We also classified the subjects in five categories
according to the distribution obtained by the FFQ. The
average total alcohol consumption for every category
estimated both by FFQ and DR was plotted separately
for men and women.
Using the reference method as control, we evaluated
the ability of our questionnaire to define abstainers
(i.e. subjects reporting alcohol consumption <1 g/day,
<1 glass of wine or of other alcoholic beverages every
2 weeks). We coded all the subjects as abstainers
or drinkers using the data collected both by FFQ and
DR. The percentage of correct self-classification
was evaluated separately for males and females, and
k-statistics were computed.16
777
RESULTS
Mean daily alcohol intakes estimated by the DR and
the two FFQ overall and in separate strata of sex and
age are presented in Table 1. Pearson correlation coefficients, de-attenuated correlation coefficients and
intraclass correlation coefficients are also given.
When compared with the DR, the two FFQ tended to
overestimate total alcohol intake. The overall estimated
mean alcohol intake was, for males, 32.5 g/day according to the DR, 37.6 g/day according to the FFQ1, and
35.5 g/day according to FFQ2. Corresponding values
for females were 10.2, 13.5 and 12.8 g/day, respectively. A trend of decreasing alcohol consumption with
increasing age emerged both in males and in females,
except for males in FFQ2.
The reproducibility of alcohol intake was better than
its validity, overall and in each sex- and age-specific
stratum. The comparison of DR with FFQ yielded
coefficients, (r,), of 0.66 for FFQ1 and 0.61 for FFQ2.
Values of 0.72 and 0.58, respectively, were found in
men, and 0.64 and 0.62 in women. Better correlations
for FFQ1 were found with respect to FFQ2, in
particular for males aged >55 years. Coefficients
adjusted for total energy (TJ, and de-attenuated ones
(rc) showed values comparable to those adjusted for
design variables only. Similar results were obtained
when FFQ1 with the first 7-DD and FFQ2 with the
second 7-DD were compared separately (data not
shown). The reproducibility of total alcohol intake was
satisfactory with r, >0.70, except for males aged 5*55
years. Similar values were obtained after adjusting the
intake for total energy (r,,), or taking into account the
intra-variability of consumption by means of (rd).
In Table 2 various types of alcoholic beverages were
considered. Mean values and the consumption variability were generally higher in the FFQ than the DR,
except for the group of other spirits in men. An
appreciable difference for beer consumption between
the two FFQ was evident in males. With reference to
the validity of specific alcoholic beverages, the lowest
values of rB emerged for beer and other spirits
consumption. The same held true for women. The
reproducibility was good, with r, >0.75 for wine in
both sexes, while for beer and other spirits the values
tended to be <0.60, with, however, higher values in
males than in females. The reproducibility of grappa
consumption was around 0.60 in both sexes. Thus, the
self-report of wine intake seemed both more reproducible and valid than that of other alcoholic beverages.
The classification in abstainers/drinkers according to the DR and FFQ2 is given in Table 3. The
percentage of misclassification for abstainers was
somewhat lower when the same analysis was made
778
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
TABLE 1 Comparison of alcohol consumption (g/day) estimated according to reference method (dietary record, DR) and two food
frequency questionnaires (FFQl and FFQl). Data from 395 participants in a study of reproducibility and validity. Italy 1990-1991
Pearson correlation coefficient*
DR
FFQl
FFQ2
DR versus FFQl
DR versus FFQ2
FFQl versus FFQ2
Mean
SD
Mean
SD
Mean
SD
All subjects
17.52
20.66
21.46
32.62
20.29
27.72
0.66
0.63
0.65
0.61
0.58
0.60
0.77
0.75
0.78
Men (130)
Age (years)
<55
5»55
33.60
30.91
27.01
25.33
38.24
36.75
37.91
37.35
33.83
37.88
32.97
35.96
0 66
0 83
0.62
0.83
0.65
0.82
0.62
0.53
0.57
0.54
0.61
0.52
0.86
0.49
0.82
0.48
0.86
0.51
All
32.52
26.22
37.62
37.54
35.51
34.16
0.72
0.68
0.71
0.58
0.55
0.57
0.73
0.71
0.73
Women (265)
Age (years)
<55
5»55
10.44
9.63
12.89
9.74
14.29
12.41
32.76
13.06
21.09
13.90
18.58
22.34
0.67
0.60
0.65
0.58
0.66
0.59
0.62
0.62
0.60
0.58
0.61
0.60
0.77
0.79
0.76
0.76
0.77
0.79
All
10.16
11.67
13.53
26.60
12.82
20.17
0.64
0.61
0.63
0.62
0.59
0.61
0.78
0.75
0.78
1
Based on log. (x+0.001) transformed values; r, adjusted for age, centre and sex when necessary; rb intakes adjusted for total energy, age, centre and
sex when necessary using regression analysis; rc de-attenuated correlation coefficients: rj Vl/[l+(j^/nXj^)], where j ^ and j j estimated on reference
method represent the within and between variances respectively, and n is the number of replicates for each volunteer, i.e. the number of days in the
DR; rd intraclass correlation coefficients: (jj - J^)/[xJ+ (n - lW*) with n = 2 ai the number of replicated measurements of FFQ.
TABLE 2 Comparison of alcohol consumption (g/day) from different beverages estimated according to reference method (dietary record,
DR) and two food frequency questionnaires (FFQl and FFQ2). Data from 395 participants in a study of reproducibility and validity.
Italy 1990-1991
Pearson correlation coefficient*
DR
FFQl
FFQ2
DR versus FFQl
DR versus FFQ2
FFQl versus FFQ2
Beverage
Mean
SD
Mean
SD
Mean
SD
r,
Wine
Beer
Grappa
Other spirits
15.78
0.69
0.29
0.76
18.49
1.79
1.08
2.18
19.65
0.75
0.44
0.62
31.14
2.06
1.55
1.87
18.01
1.24'
0.46
0.58
25.12
5.13
1.77
1.68
0.71
0.38
0.51
0.38
0.67
0.37
0.50
0.37
0.69
0.35
0.49
0.35
0.67
0.42
0.45
0.40
0.63
0.41
0.45
0.39
0.65
0.38
0.43
0.36
0.78
0.58
0.59
0.47
0.76
0.55
0.60
0.46
0.79
0.61
0.63
0.50
Men (130)
Wine
Beer
Grappa
Other spirits
28.74
1.43
0.68
1.68
23.21
2.78
1.69
3.49
34.04
1.39
1.05
1.13
35.62
2.89
2.40
2.63
30.60
2.70'
1.15
1.06
29.98
8.41
2.89
2.33
0.78
0.37
0.56
0.42
0.74
0.33
0.55
0.38
0.76
0.34
0.54
0.39
0.73
0.44
0.44
0.38
0.70
0.41
0.43
0.35
0.71
0.41
0.42
0.35
0.75
0.67
0.59
0.55
0.75
0.63
0.58
0.53
0.76
0.67
0.59
0.55
9.39
0.32
0.10
0.31
11.09
0.76
0.49
0.73
12.59
0.43
0.14
0.37
25.98
1.38
0.71
1.28
11.84
0.53
0.12
0.34
19.66
1.80
0.52
1.17
0.68
0.39
0.44
0.35
0.64
0.39
0.42
0.35
0.66
0.34
0.41
0.30
0.64
0.41
0.47
0.41
0.60
0.41
0.46
0.40
0.62
0.36
0.43
0.35
0.79
0.50
0.61
0.40
0.76
0.48
0.63
0.39
0.79
0.50
0.61
0.41
Women (265)
Wine
Beer
Grappa
Other spirits
r
b
r
c
* Based on log,, (x+0.001) transformed values; ra adjusted for age, centre and sex when accessary; rb intakes adjusted for total energy, age, centre and
sex when necessary using regression analysis; rc de-attenuated correlation coefficients: rj Vl/[l+(ii/nXjJ)], where s\ and s\ estimated on reference
method represent the within and between variances respectively, and n is the number of replicates for each volunteer, i.e. the number of days in the
DR; rd intraclass correlation coefficients: (jj - liVI^J + (n - I )J^] with n •= 2 as the number of replicated measurements of FFQ. * The difference from
the mean of FFQl was statistically significant (P < 0.05).
779
ALCOHOL CONSUMPTION IN ITALY
TABLE 3 Classification in abstainers* and alcohol drinkers according to different sources of dietary data collection (dietary record, DR)
and the second food frequency questionnaire (FFQ2). Italy 1990-1991
Reference method (DR)
Males
( n = 130)
FFQ2
Females
(n = 265)
Males & females
(n = 395)
Abstainer
Drinker
Total
Abstainer
Drinker
Total
Abstainer
Drinker
Total
Abstainer
Drinker
11
5
8
106
19
111
60
7
29
169
89
176
71
12
37
275
108
287
Total
16
114
130
67
198
265
83
312
395
k-statutic b
0.57
0.68
0.66
* Abstainer is defined as anyone with total alcohol consumption <1 g/day.
b
k = (po - Pj)/(1 - p,) where p 0 is the observed probability of concordance between FFQ2 and DR and p e is the expected probability of concordance
between FFQ2 and DR.
TABLE 4 Drinkers of various types of beverages in strata of sex." Italy 1990-1991
Males
( n = 130)
Wine (W)
Beer(B)
Grappa (G) &
other spirits (Ot)
W&B
W&(G or Ot)
B&(G or Ot)
W&(all the other
combinations)
Total
1
Females
(n = 265)
Males & females
(n = 395)
DR
FFQ1
FFQ2
DR
FFQ1
FFQ2
DR
FFQ1
FFQ2
13.1
00
0.0
26.9
1.5
3.1
24.6
0.8
1.6
27.2
0.4
0.4
40.0
2.6
1.5
34.7
34
3.8
22.5
0.3
0.3
35.7
2.3
2.1
31.4
2.5
3.0
7.7
12.3
1.5
53.1
11.5
13.8
1.5
29 3
10.0
16.9
00
31.6
14.7
154
1.2
15.6
7.9
12.0
08
4.5
9.1
10.6
0.4
4.6
12.4
14.4
1.3
27.8
9.1
12.7
1.0
12.6
9.4
12.6
0.3
13.4
87 7
87.6
85.5
74.9
69.3
66.6
79.0
75.0
72.6
The data are reported in percentages of subjects drinking different alcoholic beverages or combinations.
on FFQ1 (data not shown). Overall, 37 of 108 subjects
(30%) classified as abstainers in the FFQ2 reported >1
drink per week in the DR. The percentage was similar
in males (eight drinkers according to DR classified
themself as abstainers in FFQ2 out of a total of 19) and
females (29 of 89). K-statistics used as a measure of
chance adjusted accuracy assumed satisfactory
values: 16 0.57 and 0.68 in males and females
respectively, and 0.66 in both sexes combined.
Table 4 gives the percentage of drinkers of different
combinations of alcoholic beverages, overall and by
sex. It confirms that the subjects who drank all types of
beverages (according to DR) tended to underreport this
pattern in FFQ. Approximately 30% of males and 5% of
females reported drinking wine, beer, grappa and other
spirits in FFQ, while the corresponding figures in DR
were 53% and 16%.
Moreover, considering the source of alcohol intake,
on the average, wine represented around 90% of total
alcohol consumption. The remaining intake was due to
beer (4%), grappa (2%) and other spirits (4%). For
females, the percentage of alcohol deriving from beverages other than wine was even lower than for males (i.e.
around 5% in DR). These patterns of alcohol consumption were consistent in both questionnaires. However,
the FFQ2 showed a higher percentage consumption for
780
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Males
Females
100r
50
50
25
50
FFQ2
100
25
FFQ2
50
FIGURE 1 Plot of the mean alcohol intake (g/day) measured from dietary records (DR) in five quintiles as
defined by the FFQ2
beer, with corresponding lower values for wine (data
not shown).
Figures la (males) and lb (females) show mean daily
intakes (g/day) and the corresponding standard deviation derived from DR, in five groups defined according
to quintile distribution of drinkers in FFQ2. These
values are related to the 'true intake' and the measurement error. The first component is associated with the
estimates obtained by DR, while the measurement error
is associated with FFQ2. These plots confirm moderate
alcohol consumption among a few subjects classified as
abstainers by FFQ. Further, they show high values of
measurement error inside different quintiles, as shown
by the SD, and little agreement between FFQ2 and DR
for individuals in the extreme quintiles defined by
FFQ2 (i.e. a systematic overestimate from FFQ).
DISCUSSION
This study on validity and reproducibility of alcohol
intake is based on a Mediterranean population with a
specific pattern of alcohol intake and on the largest
data-set collected to date for this purpose. In Southern
European countries drinking alcoholic beverages is
common practice, particularly with respect to wine
during meals, and the total amount of alcohol intake
among drinkers usually shows a high inter-individual
variability.1 This gives a unique opportunity to assess
the validity of self-report of alcohol in two extreme
situations of specific interest from an epidemiological
viewpoint: self-defined abstainers and heavy drinkers.
The major findings of this study are, i) a satisfactory
level of reproducibility and validity of the pattern of
alcohol consumption across different levels and type of
alcoholic beverage intake, ii) the presence (about 30%)
of drinkers, although moderate, in the self-defined
category of abstainers as collected by FFQ, and this in
spite of a systematic tendency of FFQ to overestimate
alcohol intake as compared to DR, and iii) heavy
drinkers as defined by the FFQ include a proportion of
moderate drinkers who tended therefore to overestimate
their consumption.
The satisfactory reproducibility of total alcohol
intake and wine, which accounts for more than 90% of
alcohol consumption in Italy, is reflected by correlation
coefficients >0.75 in both sexes. These values are
comparable with those from other studies. 3 ' 7 The
validity was somewhat higher for wine than for other
beverages as well as total alcohol consumption. This is
probably accounted for by the more regular pattern of
wine consumption as compared to other alcoholic
beverages, which may be more strongly influenced by
seasonal and daily variations. This seasonal variation,
associated with a relatively low intake (less than 10%
of total alcohol consumption) may explain the difference between an acceptable level of reproducibility and
a low level of validity for grappa, other spirits and,
most notably, beer. Seasonal variations in the consumption of beer led to higher consumption of this beverage
in FFQ2, filled in during the summer period, as
compared to FFQ1.
The greatest mismatching between DR and FFQ
appeared related to the two categories 'wine alone' and
'wine & all other alcoholic beverages'. At variance
with DR, there was a tendency to report, in the FFQ, a
pattern of alcohol consumption based on wine only
(around 25% of the drinkers in males and more than
35% in females), thus overlooking a more variable
ALCOHOL CONSUMPTION IN ITALY
pattern of alcohol consumption (wine & all other
alcohol). In different countries, the same may well
happen with respect to the most popular alcoholic
beverage.
The overestimation of total alcohol intake obtained
by FFQ in elderly men can, partly or largely, be
explained by an overestimation of average amount of
alcohol per drink in the questionnaire with respect to
such age groups. Since, however, a decline in alcohol
consumption with age was evident in the present as well
as in other investigations,17 it is also possible that recall
of past heavier drinking may have inflated recent
reported intake in the elderly.
Analysis of the subgroup that, according to the FFQ,
drank alcohol only during meals (n = 183, 48% of the
subject) gave better correlations, particularly with
regard to validity (data not shown). Thus, the FFQ is an
especially good instrument in order to collect alcohol
intake in drinkers with regular drinking patterns. Conversely, lower values of validity for irregular drinkers
(occasional drinkers, subjects drinking both during and
outside of meals, etc) may be due to seasonal variations, inadequacy of FFQ to capture irregular patterns
of consumption or/and inadequacy of DR as a reference
method (e.g. insufficiency of 14-day record).
The presence of a relevant number of drinkers,
although moderate, in the category 'abstainers' of the
FFQ should also be carefully considered. Such a misclassification can derive from hesitation to admit
alcohol drinking or misunderstanding of the meaning of
the category 'alcohol abstainers'. In a country like Italy,
where wine and other alcoholic beverage consumption
is common, the first source of misreporting should be
negligible. Misclassification of light drinkers as
abstainers may be more common among the minority of
drinkers who do not drink wine during meals. Whatever
the major underlying mechanisms, this confirms that
abstainers in Italy are a subgroup for which an appreciable problem of reproducibility and validity exists.
Consequently, the use of abstainers as the reference
category in epidemiological studies on alcohol and
disease should be viewed with due caution.18 This is of
particular interest also considering that the tendency to
overestimate alcohol consumption in a number of
moderate drinkers could attenuate the relative risks in
higher consumption defined by means of FFQ.
ACKNOWLEDGEMENTS
This work was conducted within the framework of CNR
(Italian National Research Council) Applied Project:
'Clinical Application of Oncological Research' (Contracts No. 94.01119.PF39, No. 94.01268.PF39 and
781
No. 94.01321.PF39) and with the contribution of the
Italian Association for Cancer Research. The authors
thank Dr Oriana Nanni, Dr Attilio Giacosa and
Dr Renato Talamini for their help in the study
organization, Ms Patrizia Gnagnarella and Ms Olinda
Volpato for their advice in the questionnaire preparation and interviewers' training, and Mrs Angela R
Simm for editorial assistance.
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