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Web-based questionnaires allow collecting data quickly, with minimal costs from large sample groups and through Web-based self-administered forms. Until recently, there has been a lack of evidence from large-scale epidemiological studies and nutrition surveys that have evaluated the comparison between traditional and new technologies to measure dietary intake.
This study aimed to compare results from the general baseline questionnaire (Q_0) and the 10-year follow-up questionnaire (Q_10) in the Seguimiento Universidad de Navarra (SUN) prospective cohort, obtained from different subjects, some of whom used a paper-based version, and others used a Web-based version. Both baseline and 10-year assessments included a validated 136-item semiquantitative food-frequency questionnaire (FFQ), used to collect dietary intake.
The SUN project is a prospective cohort study (with continuous open recruitment and many participants who were recently recruited). All participants were university graduates. Participants who completed the validated FFQ at baseline (FFQ_0, n=22,564) were selected. The variables analyzed were classified into 6 groups of questions: (1) FFQ (136 items), (2) healthy eating attitudes (10 items), (3) alcohol consumption (3 items), (4) physical activity during leisure time (17 items), (5) other activities (24 items), and (6) personality traits (3 items). Multiple linear and logistic regression models were used to assess the adjusted differences between the mean number of missing values and the risk of having apparently incorrect values for FFQ items or mismatches and inconsistencies in dietary variables.
Only 1.5% (339/22564) and 60.71% (6765/11144) participants reported their information using the Web-based version for Q_0 and Q_10, respectively, and 51.40 % (11598/22564) and 100.00% (11144/11144) of participants who completed the Q_0 and Q_10, respectively, had the option of choosing the Web-based version. Sociodemographic, lifestyle, health characteristics, food consumption, and energy and nutrient intakes were similar among participants, according to the type of questionnaire used in Q_10. Less than 0.5% of values were missing for items related to healthy eating attitudes, alcohol consumption, and personality traits in the Web-based questionnaires. The proportion of missing data in FFQ, leisure time physical activity, and other activities was higher in paper-based questionnaires than Web-based questionnaires. In Web-based questionnaires, a high degree of internal consistency was found when comparing answers that should not be contradictory, such as the frequency of fruit as dessert versus total fruit consumption and the frequency of fried food consumptions versus oil consumption.
Incorporating a Web-based version for a baseline and 10-year questionnaire has not implicated a loss of data quality in this cohort of highly educated adults. Younger participants showed greater preference for Web-based questionnaires. Web-based questionnaires were filled out to a greater extent and with less missing items than paper-based questionnaires. Further research is needed to optimize data collection and response rate in Web-based questionnaires.
A key aspect in epidemiology is the adequate classification of exposure [
Therefore, we aimed to compare results from the general baseline questionnaire (Q_0) and the 10-year follow-up questionnaire (Q_10) of the SUN prospective cohort obtained in different subjects, some of whom used a paper-based version, and others used a Web-based version.
The SUN project is a multipurpose and prospective Spanish cohort of university graduates, designed to study the impact of several sociodemographic, nutrition, and lifestyle characteristics on the prevention of noncommunicable diseases. Open enrollment began in 1999. The design and methods used in the SUN project have been formerly described in detail elsewhere [
Flow chart of the study.
In the SUN cohort, the Q_0, and follow-up questionnaires are self-administered. The Q_0 includes information about sociodemographic variables (eg, sex, age, marital status, and employment status), lifestyle-related variables (eg, smoking status, physical activity, and special diets), anthropometric variables (weight, height), and clinical variables (medical history, family health history, blood pressure levels, medication use, and not gaining more than 5 kg of weight in previous years). On the other hand, the Q_10 collected information on a wide array of characteristics, including weight, height, marital status, and diagnosis of several diseases. Both of these general questionnaires can be filled out in paper form or on the Web, and they are exactly equivalent. The paper-based FFQ comprises 136 food and beverage items, categorized into 9 frequency categories of consumption. These items capture the usual consumption of listed foods during the previous year. There are 9 options for the average frequency of consumption (never or almost never: at least 6 times per day). The Web-based FFQ is a Web-based questionnaire, with a format very similar to that of the paper-based version including the same items.
Nutrient intakes were calculated as the frequency multiplied by the nutrient composition of specified portion sizes for each food item by using an ad hoc computer program that was specifically developed for this aim. A trained dietitian updated the nutrient database using the latest available information from food composition tables for Spain [
Physical activity information is obtained at baseline through a questionnaire validated in Spain [
The aim of our study was not to compare repeated measurements of the same variables within the same subjects using 2 different methods; the aim of this study was to compare the reliability and comprehensiveness of the information gathered with each of both methods (paper-based or Web-based) from different subjects. Descriptive statistics were used to describe the differences at baseline and follow-up between participants who completed the questionnaire in paper-based version and among those who filled out the Web-based version. We used means and SDs for continuous variables or percentages for categorical variables. Multiple linear regression models were used to assess the association between the type of questionnaire (paper or Web-based version) and the differences in the mean number of missing values at baseline. Logistic regression models were run to assess the relationship between the type of questionnaire at baseline and the risk of having implausible data of food items and mismatches or inconsistencies in dietary variables. Both analyses were adjusted for sex, age, level of education (bachelor, graduate, postgraduate, and doctorate), and year entering the cohort (1999-2000, 2001, 2002-2003, 2004, 2005-2007, and 2008-2017). The Q_0 paper-based version was always considered as the reference category. Analyses were performed with STATA version 12 (STATA Corp). All
We have compared several potential measures of data quality between Web-based and paper-based data collection at baseline and at 10-year follow-up. Overall, the sociodemographic, lifestyle, and health characteristics were well balanced between the 2 approaches for administering the questionnaires, particularly Q_10, which had a higher number of participants and similar year of completion (
Subjects who fulfilled the paper-based Q_0 were more likely to be older, married, workers, current smokers and ex-smokers, and they were more likely to have a lower level of university education. Moreover, they were less active and showed a higher prevalence of hypertension, cancer, diabetes, and weight gain in the past 5 years. On the other hand, participants who completed the Web-based Q_10 were more likely to be men, younger, physically active during leisure time, not married, workers, never smokers, had a higher adherence to the Mediterranean diet, and generally had less prevalence of chronic disease related to diet. Beneficial changes in the consumption of most food and macronutrients and a positive response to dietary attitudes were observed after 10 years of follow-up, mainly when comparing the paper FFQ_0 and FFQ_10 (
Baseline characteristics, mean (SDs), or percentages, of participants who filled out the paper- or Web-based questionnaires at baseline and at 10-year follow-up.
Variable | Baseline questionnaires (Q_0) | 10-year of follow-up questionnaires (Q_10) | |||
Paper-based (n=22,225) | Web-based (n=339) | Paper-based (n=4379) | Web-based (n=6765) | ||
Age (years), mean (SD) | 37.5 (12.4) | 34.0 (11.7) | 40.1 (12.8) | 36.2 (10.9) | |
Men, n (%) | 8592 (38.66) | 129 (38.1) | 1714 (39.14) | 2786 (41.18) | |
Year of completing the questionnaire, mean (SD) | 2004 (4) | 2012 (4) | 2002 (2) | 2002 (2) | |
Body Mass Index (kg/m2), mean (SD) | 23.5 (3.6) | 23.6 (3.7) | 23.6 (3.5) | 23.4 (3.4) | |
|
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Married | 10973 (49.37) | 108 (31.9) | 2457 (56.11) | 3336 (49.31) |
|
Single, widowed, divorced, and others | 11252 (50.63) | 231 (68.1) | 1922 (43.89) | 3429 (50.69) |
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Worker | 17463 (78.57) | 238 (70.2) | 3419 (78.08) | 5475 (80.93) |
|
Retired, housewife, and unemployed | 4762 (21.43) | 101 (29.8) | 960 (21.92) | 1290 (19.07) |
Educational level (years of education), mean (SD) | 5.0 (1.5) | 5.5 (1.6) | 5.0 (1.5) | 5.0 (1.5) | |
Physical activity during leisure time (metabolic equivalents-h/week), mean (SD) | 27.3 (24.3) | 30.4 (25.5) | 27.0 (24.2) | 27.1 (23.1) | |
Mediterranean diet score (0 to 9 score), mean (SD) | 4.3 (1.8) | 4.5 (1.7) | 4.2 (1.8) | 4.1 (1.8) | |
TV (hours/week), mean (SD) | 5.2 (2.1) | 5.8 (2.0) | 5.1 (2.0) | 5.5 (2.0) | |
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Current smokers | 4796 (21.57) | 38 (11.2) | 983 (22.45) | 1500 (22.17) |
|
Ex-smokers | 6202 (27.91) | 74 (21.8) | 1299 (29.66) | 1872 (27.67) |
|
Never smokers | 10597 (47.68) | 224 (66.1) | 2097 (47.89) | 3303 (50.16) |
Hypertension at baseline, n (%) | 1933 (8.70) | 21 (6.2) | 437 (9.98) | 483 (7.14) | |
Cancer at baseline, n (%) | 843 (3.79) | 12 (3.5) | 175 (4.00) | 232 (3.43) | |
Diabetes at baseline, n (%) | 419 (1.89) | 3 (0.9) | 79 (1.8) | 86 (1.27) | |
Dyslipemia at baseline, n (%) | 1495 (6.73) | 29 (8.6) | 312 (7.1) | 406 (6.00) | |
Cardiovascular disease at baseline, n (%) | 335 (1.51) | 7 (2.1) | 70 (1.6) | 80 (1.18) | |
Weight gain in past 5 years, n (%) | 6692 (30.11) | 93 (27.4) | 1388 (31.70) | 2086 (30.84) | |
Special diets, n (%) | 1797 (8.09) | 42 (12.4) | 340 (7.76) | 493 (7.29) | |
Between-meals snacking, n (%) | 7723 (34.75) | 135 (39.8) | 1499 (34.23) | 2331 (34.5) | |
Dietary supplement use, n (%) | 4306 (19.37) | 77 (22.7) | 779 (17.79) | 1152 (17.0) |
Baseline food consumption, energy and nutrient intakes, and dietary attitudes of the participants, of the Seguimiento Universidad de Navarra cohort, who filled out the paper-based and Web-based questionnaire at baseline and at 10-year follow-up.
Variable | Baseline questionnaires (Q_0) | 10-year of follow-up questionnaires (Q_10) | ||
Paper-based (n=22,225) | Web-based (n=339) | Paper-based (n=4379) | Web-based (n=6765) | |
Energy intake (kcal/d), mean (SD) | 2532 (957) | 2342 (882) | 2566 (985) | 2537 (904) |
Protein intake (% total energy), mean (SD) | 18.1 (3.5) | 18.1 (4.7) | 18.0 (3.7) | 17.7 (3.3) |
Carbohydrate intake (% total energy), mean (SD) | 43.3 (7.7) | 41.9 (10.6) | 43.4 (8.0) | 43.6 (7.3) |
Fat intake (% total energy), mean (SD) | 36.6 (6.8) | 35.8 (8.9) | 36.6 (7.1) | 36.7 (6.5) |
Polyunsaturated fatty acid intake (% total energy), mean (SD) | 5.2 (1.6) | 4.9 (1.7) | 5.3 (1.7) | 5.3 (1.6) |
Monounsaturated fatty acid intake (% total energy), mean (SD) | 15.7 (3.8) | 15.3 (4.6) | 15.8 (4.0) | 15.7 (3.7) |
Saturated fatty acid intake (% total energy), mean (SD) | 12.5 (3.4) | 11.6 (3.9) | 12.5 (3.6) | 12.6 (3.1) |
Fiber intake (g/d), mean (SD) | 30.0 (16.5) | 30.6 (17.7) | 30.7 (17.5) | 28.8 (14.7) |
Cholesterol intake (mg/d), mean (SD) | 440.5 (208.7) | 401.2 (183.2) | 447.8 (218.5) | 440.0 (185.1) |
Alcohol intake (g/d), mean (SD) | 6.8 (10.8) | 5.1 (7.6) | 6.9 (11.4) | 7.0 (10.7) |
Fruits (g/d), mean (SD) | 370.9 (354.4) | 353.9 (341.3) | 380.6 (360.3) | 349.1 (345.6) |
Vegetables (g/d), mean (SD) | 555.8 (409.8) | 611.7 (533.0) | 554.4 (446.0) | 519.6 (336.1) |
Nuts (g/d), mean (SD) | 8.4 (16.6) | 13.6 (27.3) | 8.5 (16.5) | 7.8 (16.1) |
Legumes (g/d), mean (SD) | 24.2 (25.2) | 23.3 (17.9) | 24.6 (25.7) | 23.3 (20.8) |
Dairy products (g/d), mean (SD) | 209.4 (226.0) | 136.1 (150.9) | 222.3 (237.0) | 231.1 (227.6) |
Meats (g/d), mean (SD) | 185.9 (105.4) | 175.4 (94.2) | 185.7 (110.0) | 181.7 (92.9) |
Fish (g/d), mean (SD) | 103.0 (81.9) | 100.3 (75.1) | 104.8 (87.6) | 98.2 (69.8) |
Olive oil (g/d), mean (SD) | 16.0 (14.5) | 16.7 (16.1) | 16.1 (15.1) | 15.6 (14.3) |
Fast food (g/d), mean (SD) | 23.4 (27.5) | 27.8 (23.6) | 19.7 (25.9) | 22.7 (29.0) |
Do you try to eat more fiber? (% yes), n (%) | 13153 (59.18) | 223 (65.8) | 2644 (60.38) | 3820 (56.47) |
Do you try to eat more fruit? (% yes), n (%) | 15209 (68.43) | 246 (72.6) | 3059 (69.86) | 4410 (65.19) |
Do you try to eat more vegetables? (% yes), n (%) | 17768 (79.95) | 271 (80.0) | 3551 (81.09) | 5303 (78.39) |
Do you try to eat more fish? (% yes), n (%) | 13170 (59.26) | 201 (59.3) | 2644 (60.38) | 3820 (56.47) |
Do you avoid the consumption of butter? (% yes), n (%) | 15649 (70.41) | 247 (72.9) | 3148 (71.89) | 4574 (67.61) |
Do you try to eat less fat? (% yes), n (%) | 17312 (77.89) | 270 (79.7) | 3473 (79.31) | 5079 (75.08) |
Do you try to eat less meat? (% yes), n (%) | 7747 (34.86) | 145 (42.8) | 1589 (36.29) | 2205 (32.59) |
Do you try to remove fat from meat? (% yes), n (%) | 16549 (74.46) | 187 (55.2) | 3321 (75.84) | 5064 (74.86) |
Do you add sugar to some beverages? (% yes), n (%) | 6712 (30.20) | 99 (29.2) | 1308 (29.87) | 2125 (31.41) |
Do you try to eat less sweets and pastries? (% yes), n (%) | 14098 (63.43) | 244 (72.0) | 2720 (62.11) | 3989 (58.87) |
We have found similar results to those previously published [
Generally, the adjusted differences in the 6 sections evaluated at Q_0 were low. In all cases, they were lower than 3.5%, even for questions on healthy eating attitudes, alcohol consumption, and personality traits; they were very low, lower than 0.5%. However, when we compared participants who completed Q_0 at baseline using the Web-based versus paper-based version, we found some contradictory data. Thus, the mean amount of missing data in the FFQ_0 and physical activity during leisure time questions was significantly higher among subjects who had completed the Web-based version (ß=3.3, 95% CI 2.03-4.64 and ß=2.01, 95% CI 1.45-2.57, respectively) but significantly lower in the other activity questions (ß=–2.01, 95% CI –3.04 to –1.35). Overall, the percentage of participants with implausible data on food consumption in the FFQ was always lower than 3% in participants who used the paper-based version at baseline or at 10-year follow-up (
However, we found the following exception: the implausible reporting of nuts consumption, accounting for more than 16% of participants. On the other hand, when we considered all participants, generally, no significant differences among food group consumption were found, except for the implausible reporting of nuts consumption, more probable in these same subjects—odds ratio (OR) 1.54 (95% CI 1.20-1.99). When we classified participants according to the type of questionnaire chosen at 10-year follow-up, the implausible reporting of legume and meat consumption was less frequent in those who collected the Web-based version. The number of participants with implausible olive oil consumption was 1 among those who used the Web-based version and 0 among those who used the paper-based version. For this reason, we could not present the OR for Web-based versus paper-based version. Finally, overall, in both the paper-based and Web-based FFQ_0, the items with higher frequency of mismatches and inconsistencies were total energy intake (near 10%) and self-reported alcohol consumption (approximately 2%;
On the contrary, mismatches and inconsistencies were lower in reported consumption of fruit dessert versus total fruit consumption and fried food versus oil consumption. In addition, subjects who filled the Q_0 via internet exhibited a significantly higher risk of presenting inconsistencies in reporting alcohol consumption and wine consumption versus total alcohol intake, compared with those who chose the paper-based version: adjusted OR 3.58 (95% CI 2.01-6.22) and OR 3.01 (95% CI 1.21-7.48), respectively, although the mismatches in relation to total energy intake outside of the reference subset had a lower risk: OR 0.31 (95% CI 0.17-0.56).
Adjusted differences for the mean number of missing values in paper-based or Web-based questionnaire at baseline (Beta regression coefficients and 95% CIs). The Q_0 paper-based version was always considered as the reference category.
Missing values | All participants | Participants with successful 10-year follow-up | ||
Missing values in baseline questionnairea, mean (n=22,225) | Beta (95% CI)b,c (n=339) | Missing values in 10-year of follow-up questionnaired, mean (n=4379) | Beta (95% CI)b,e (n=6765) | |
Missing values in the food-frequency questionnaire (136 items) | 12.93 | 3.33 (2.03 to 4.64)f | 14.54 | –1.16 (–1.63 to –0.69)f |
Missing values in the healthy eating attitudes (10 items) | 0.29 | 0.13 (0.001 to 0.25)g | 0.28 | 0.002 (–0.04 to 0.04) |
Missing values in the alcohol consumption questions (5 items) | 0.05 | 0.09 (0.05 to 0.12)f | 0.07 | –0.01 (–0.03 to 0.0002) |
Missing values in the physical activity during leisure time questions (17 items) | 2.99 | 2.01 (1.45 to 2.57)f | 4.20 | –0.21 (–0.43 to 0.01) |
Missing values in the other activities questions (24 items) | 4.60 | –2.20 (–3.05 to –1.35)f | 4.86 | –0.45 (–0.74 to –0.16)h |
Missing values in the personality traits questions (3 items) | 0.04 | 0.07 (0.04 to 0.10)f | 0.04 | 0.007 (–0.004 to 0.02) |
aQ_0, paper-based.
bAdjusted for sex, age, level of education (bachelor, graduate, postgraduate, and doctorate) and year entering the cohort (1999-2000, 2001, 2002-2003, 2004, 2005-2007, and 2008-2017).
cIn the mean number of missing values in baseline questionnaire (Q_0, Web-based -paper-based).
dQ_10, paper-based.
eIn the mean number of missing values in 10-year of follow-up questionnaire (Q_10, Web-based -paper-based).
f
g
h
Percentage of participants with implausible report of food items in the paper-based or Web-based questionnaire at baseline. Odds ratios and 95% CIs to have implausible data in these dietary variables. The Q_0 paper-based version was always considered as the reference category.
Implausible reporta | All participants | Participants with successful 10-year follow-up | ||
Q_0b Paper-based (n=22,225) | ORsc (95% CI)d for Web-based versus paper-based in Q_0 (n=339) | Q_10e Paper-based (n=4379) | ORs (95% CI)d for Web-based versus paper-based in Q_10 (n=6765) | |
Fruit consumption | 1.77 | 0.49 (0.15-1.59) | 1.99 | 0.77 (0.57-1.04) |
Vegetable consumption | 1.25 | 1.03 (0.44-2.43) | 1.21 | 0.71 (0.48-1.06) |
Legume consumption | 2.84 | 1.07 (0.60-1.92) | 2.88 |
|
Fish consumption | 0.75 | 0.76 (0.18-3.22) | 0.73 | 0.81 (0.49-1.32) |
Meat consumption | 0.62 | 0.33 (0.00-1.79)g | 0.8 |
|
Dairy products consumption | 1.09 | 0.19 (0.00-1.002)g | 1.42 | 0.77 (0.54-1.09) |
Cereal consumption | 0.85 | 0.79 (0.19-3.37) | 1.14 | 0.85 (0.57-1.27) |
Nuts consumption | 16.67 | 1.54 (1.20-1.99)i | 16.4 | 0.94 (0.85-1.05) |
aFor each food group, the consumption was considered implausible if it fell outside the 25th percentile minus 3 times this interquartile range or 75th percentile plus 3 times this interquartile range.
bQ_0: Baseline questionnaire.
cOR: odds ratio.
dAdjusted for sex, age, level of education (bachelor, graduate, postgraduate, and doctorate), and year entering the cohort (1999-2000, 2001, 2002-2003, 2004, 2005-2007, and 2008-2017).
eQ_10: 10-year of follow-up questionnaire.
f
gExact logistic regression, as there was 0% of missing values in the Web-based questionnaire (unadjusted).
h
i
Percentage of participants with mismatches and inconsistencies in dietary variables the paper-based or the Web-based questionnaire at baseline. Odds ratios and 95% CIs for presenting mismatches and inconsistencies in dietary variables.
Mismatches and inconsistencies in dietary variables | All participants | Participants with successful 10-year follow-up | ||
Q_0a (paper- based; n=22,225) | ORsb (95% CI)cfor Web-based versus paper-based in Q_0 (n=339) | Q_10d (paper-based; n=4379) | ORs (95% CI)c for Web-based versus paper-based in Q_10 (n=6765) | |
Total energy intake outside the predefined limits (Willett; <800 or >4000 kcal/d for men, <500 or >3500 kcal/d for women) | 9.49 | 0.77 (0.54-1.13) | 10.16 | 1.14 (0.99-1.30) |
Total energy intake outside of the reference subset (<P1 or >P99) | 1.96 |
|
2.19 | 1.23 (0.93-1.63) |
Total energy intake outside of the reference subset (<P5 or >P95) | 9.96 | 0.73 (0.52-1.02) | 10.46 | 1.11 (0.98-1.27) |
Inconsistencies in reporting fruit dessert versus total fruit consumption | 0.14 | 3.06 (0.36-26.0) | 0.21 | 0.41 (0.14-1.18) |
Inconsistencies in reporting fried food consumption versus oil consumption | 0.81 | 1.63 (0.37-7.07) | 1.14 | 0.70 (0.45-1.07) |
Inconsistencies in reporting alcohol consumption | 2.25 |
|
2.72 | 1.02 (0.79-1.30) |
Inconsistencies in reporting wine consumption versus total alcohol intake | 1.45 |
|
2.01 | 1.20 (0.89-1.62) |
aQ_0: Baseline questionnaire.
bOR: odds ratio.
cAdjusted for sex, age, level of education (bachelor, graduate, postgraduate and doctorate), and year entering the cohort (1999-2000, 2001, 2002-2003, 2004, 2005-2007, and 2008-2017).
dQ_10: 10-year of follow-up questionnaire.
e
f
To the best of our knowledge, our research is the first to compare the quality of the answers, at baseline and after a 10-year follow-up period, in different subjects in a large prospective cohort, where some of them used the traditional version (paper-based) and others used a new method (Web-based) for data collection in a large prospective cohort. Our most important objective was to compare the respective ability of each method (Web-based or paper-based) to gather the relevant information in a reliable and comprehensive manner. The overall response rates in Q_0 were higher for the paper-based version than the Web-based version, 98.5% and 1.5%, respectively, as the electronic version of the questionnaire has only been available since 2004. In addition, the paper-based version was always offered as the first choice. However, in Q_10, the proportion of participants choosing the Web-based version was 61%, because of the fact that if participants are given a choice, they prefer the electronic version. A previous publication suggested that it could be useful to offer all subjects both a paper-based and a Web-based version of a long-term instrument, such as the FFQ, to avoid selection bias [
The strengths of the SUN study are its high retention rate (91%) [
food-frequency questionnaire
baseline semiquantitative food-frequency questionnaire
10 years of follow-up food-frequency questionnaire
metabolic equivalent
odds ratio
baseline questionnaire
10-year of follow-up questionnaire
Seguimiento Universidad de Navarra
The authors thank Maria Soledad Hershey for her help in the English edition, the participants of the SUN cohort for their continued involvement in the project, and all of the members of the SUN study for their support and collaboration. The University of Navarra Follow-Up (SUN) study has received funding from the Spanish Ministry of Health and European Regional Development Fund (Grants PI10/02993, PI10/02658, PI13/00615, PI14/01668, PI14/01798, PI14/1764, PI17/01795, RD06/0045, G03/140, and FIS: PI17/01795) as well the Navarra Regional Government (45/2011, 122/2014).
MAMG was involved with the conception and design of the study. Analysis and interpretation of the data was conducted by IZ, SS, MBR, and MAMG. IZ and SS wrote the first draft. All the authors were involved in the critical revision of the article for important intellectual content and final approval of the article.
None declared.