Study Participation and Composition
Adults
Data collection
Data collection began in March 2024 in Denmark, Iceland, Norway, and Sweden. Data collection finished in May 2024 in Iceland and Norway, in July 2024 in Sweden, and in September 2024 in Denmark, where a new sample required a pause from May to July. In Finland, data collection was postponed due to contracting procedures taking longer than anticipated. As a result, data was collected between September and November 2024.
Among adult participants, the average duration of telephone interviews was approximately 13 minutes, while completing the online questionnaire took around 14 minutes on average.
Adults Children Strengths and Limitations References |
Adults
Data collection
Data collection began in March 2024 in Denmark, Iceland, Norway, and Sweden. Data collection finished in May 2024 in Iceland and Norway, in July 2024 in Sweden, and in September 2024 in Denmark, where a new sample required a pause from May to July. In Finland, data collection was postponed due to contracting procedures taking longer than anticipated. As a result, data was collected between September and November 2024.
Among adult participants, the average duration of telephone interviews was approximately 13 minutes, while completing the online questionnaire took around 14 minutes on average.
Denmark* | 18-03-24 | 05-08-24 | 10-09-24 |
|---|---|---|---|
Norway | 20-03-24 | 28-05-24 | 29-05-24 |
Sweden | 21-03-24 | 05-07-24 | 05-07-24 |
Finland | 16-09-24 | 05-11-24 | 08-11-24 |
Iceland | 20-03-24 | 24-05-24 | 24-05-24 |
* Data collection was paused from 13-05-24 to 22-07-24 due to sample shortage and waiting time in the process of acquiring a new sample.
Participation Rates
From a simple random sample of 85,000 adults, 40% were successfully enriched with telephone numbers. The enrichment rate varied considerably across countries, ranging from 27% in Finland to 81% in Iceland. From the enriched sample, 26,002 adults were randomly selected and invited to participate in in the survey in 2024. The overall response rate across the Nordic countries was 19%, with country-specific rates ranging from 12% in Sweden to 30% in Iceland.
In total, 5,059 adults participated in in the survey in 2024. However, one participant, aged 73, was excluded from the final dataset due to being well outside the target population (18–65 years). Additionally, four participants were invalidated due to extreme height and weight. Consequently, the final number of participants included in the analysis was 5,054.
The primary reason for non-participation among adults was that interviewers were unable to reach the invited individuals within the maximum number of call attempts. The second most common reason was that individuals declined to participate. In Sweden, incorrect telephone numbers were also a major contributor to the high non-participation rate, whereas in Finland, frequent occurrences of busy lines or voicemail were common barriers to participation.
Sample a (n) | 20000 | 20000 | 10000 | 10000 | 25000 | 85000 |
|---|---|---|---|---|---|---|
Enriched b (n, %) | 6537 (33) | 5367 (27) | 8050 (81) | 5393 (54) | 8297 (33) | 33644 (40) |
Invited c (n) | 4421 | 5011 | 3401 | 4872 | 8297 | 26002 |
Participants (n) | 1004 | 1020 | 1023 | 1011 | 1001 | 5059 |
Response rate (%) | 23 | 20 | 30 | 21 | 12 | 19 |
a Simple random sample from national population registers.
b Individuals from the simple random sample enriched with telephone numbers.
c Individuals randomly selected from the enriched sample.
b Individuals from the simple random sample enriched with telephone numbers.
c Individuals randomly selected from the enriched sample.
Completed a | 1004 | 1020 | 1023 | 1011 | 1001 | 5059 |
Reasons for non-participation | ||||||
Appointment b | 29 | 50 | 55 | 49 | 36 | 219 (1%) |
Callback c | 10 | 476 | 158 | 74 | 15 | 733 (3%) |
Not in the target group (screened) d | 180 | 107 | 33 | 89 | 204 | 613 (3%) |
Refusal e | 1142 | 847 | 655 | 1156 | 1018 | 4818 (23%) |
Refusal (Black list) f | 8 | 21 | 2 | 0 | 46 | 77 (0.4%) |
Timeout Callback g | 1836 | 2202 | 1374 | 2427 | 5290 | 13129 (63%) |
Wrong number h | 212 | 288 | 101 | 66 | 687 | 1354 (6%) |
Total non-participation | 3417 | 3991 | 2378 | 3861 | 7296 | 20943 |
a Completed: Interview completed.
b Appointment: Participant was contacted, and a callback was scheduled, however subsequent attempts were unsuccessful.
c Callback: Includes busy line or voicemail. No direct contact was made with the participant.
d Not in target group (screened): Participant did not meet the inclusion criteria due to age, incorrect name or address, or language barriers.
e Refusal: Participant declined to participate.
f Refusal (Blacklist): Listed on Norstat’s do-not-contact list after requesting not to be contacted again in a previous Norstat-survey.
g Timeout Callback: Maximum number of call attempts was reached without contact.
h Wrong Number: The dialled number was non-existent.
b Appointment: Participant was contacted, and a callback was scheduled, however subsequent attempts were unsuccessful.
c Callback: Includes busy line or voicemail. No direct contact was made with the participant.
d Not in target group (screened): Participant did not meet the inclusion criteria due to age, incorrect name or address, or language barriers.
e Refusal: Participant declined to participate.
f Refusal (Blacklist): Listed on Norstat’s do-not-contact list after requesting not to be contacted again in a previous Norstat-survey.
g Timeout Callback: Maximum number of call attempts was reached without contact.
h Wrong Number: The dialled number was non-existent.
Characteristics of adult participants
Across the Nordic countries, 73% of respondents completed a telephone interview, while 27% responded via the online questionnaire. In Iceland, 80% participated by telephone and 20% completed the online questionnaire.
The samples of adults aged 18–65 years were drawn from national registers based on records as of October 1, 2023. Since data collection started in spring (and in Finland during autumn), the participants’ actual ages at the time of data collection ranged from 18 to 66 years. 66 year olds were included in the 45–65 year age group in tables and analyses.
In all Nordic countries, more women than men participated (53% vs. 47%). Participation was highest among the oldest age group (63%) and lowest among the youngest age group (9%). Moreover, participation was highest among individuals with higher levels of education (58%), particularly in Norway (63%), whereas participation was lowest among those with the lowest level of education (5%). Compared to the general population in each country, women, 45–65-year-olds, and those with a high level of education were overrepresented in the survey ( Appendix 4 ). Conversely, men, 18–29-year-olds, and those with a low level of education were underrepresented. To account for these discrepancies, survey weights were applied in the different analyses.
Education Group | n=1000 | n=1018 | n=1016 | n=1006 | n=994 | n=5034 |
|---|---|---|---|---|---|---|
Low | 55 (5.5%) | 34 (3.3%) | 118 (11.6%) | 31 (3.1%) | 32 (3.2%) | 270 (5.4%) |
Medium | 367 (36.7%) | 434 (42.6%) | 313 (30.8%) | 338 (33.6%) | 377 (37.9%) | 1829 (36.3%) |
High | 578 (57.8%) | 550 (54.0%) | 585 (57.6%) | 637 (63.3%) | 585 (58.9%) | 2935 (58.3%) |
Age Group | n=1004 | n=1020 | n=1021 | n=1010 | n=999 | n=5054 |
18-29 | 115 (11.5%) | 71 (7.0%) | 86 (8.4%) | 121 (12.0%) | 78 (7.8%) | 471 (9.3%) |
30-44 | 248 (24.7%) | 248 (24.3%) | 307 (30.1%) | 245 (24.3%) | 335 (33.5%) | 1383 (27.4%) |
45+ | 641 (63.8%) | 701 (68.7%) | 628 (61.5%) | 644 (63.8%) | 586 (58.7%) | 3200 (63.3%) |
Sex | n=1004 | n=1020 | n=1021 | n=1010 | n=999 | n=5054 |
Male | 482 (48.0%) | 480 (47.1%) | 439 (43.0%) | 499 (49.4%) | 463 (46.3%) | 2363 (46.8%) |
Female | 522 (52.0%) | 540 (52.9%) | 582 (57.0%) | 511 (50.6%) | 536 (53.7%) | 2691 (53.2%) |
Survey method | n=1004 | n=1020 | n=1021 | n=1010 | n=999 | n=5054 |
CATI | 710 (70.7%) | 724 (71.0%) | 820 (80.3%) | 740 (73.3%) | 708 (70.9%) | 3702 (73.2%) |
CAWI | 294 (29.3%) | 296 (29.0%) | 201 (19.7%) | 270 (26.7%) | 291 (29.1%) | 1352 (26.8%) |
Children
Data collection
Data collection began in March 2024 in Denmark, Iceland, Norway, and Sweden. Data collection ended in April in Iceland and Norway, June in Sweden, and August in Denmark. In Finland, data collection was postponed due to contracting procedures taking longer than anticipated. As a result, data was collected between September and November 2024.
For child participants, a parent or guardian completed the interview or online questionnaire. Telephone interviews lasted about 11 minutes on average, and the online questionnaire took approximately 13 minutes to complete.
Denmark | 18-03-2024 | 09-05-24 | 27-08-24 |
|---|---|---|---|
Norway | 20-03-2024 | 16-04-24 | 17-04-24 |
Sweden | 21-03-2024 | 12-06-24 | 24-06-23 |
Finland | 16-09-2024 | 21-10-24 | 07-11-24 |
Iceland | 20-03-2024 | 22-04-23 | 22-04-24 |
Participation Rates
From a simple random sample of 42,968 children, 40% were successfully enriched with telephone numbers. As with adults, the enrichment rate among children varied significantly across countries, ranging from 22% in Finland to 84% in Iceland. From the enriched sample, 12,450 children were randomly selected, and their parents or guardians were invited to participate in the study. The overall response rate across the Nordic countries was 20%, with country-specific rates ranging from 13% in Sweden to 27% in Iceland.
In total, 2,538 children participated in in the survey 2024. However, one participant was excluded because it was entered twice in the dataset, another was excluded for missing an ID number, and two participants were invalidated due to extreme height and weight. Consequently, the final number of participants included in the analysis was 2,534.
As with adults, the primary reason for non-participation among children was that interviewers were unable to reach the parents or guardians of participants within the maximum number of call attempts. An exception was Norway, where the most frequent reason for non-participation was repeated occurrences of busy lines or voicemail. Both refusals to participate and the occurrence of busy lines and voicemail were common reasons for non-participation across countries. In Iceland, uniquely, the second most common reason for non-participation was unsuccessful follow-up calls to scheduled telephone interviews. In Sweden, incorrect telephone numbers were also a relatively frequent reason for non-participation.
Sample a (n) | 5000 | 15468 | 5000 | 5000 | 12500 | 42968 |
|---|---|---|---|---|---|---|
Enriched b (n, %) | 2134 (43) | 3438 (22) | 4200 (84) | 2816 (56) | 4632 (37) | 17220 (40) |
Invited c (n) | 2134 | 2291 | 1883 | 2347 | 3795 | 12450 |
Participants (n) | 509 | 503 | 510 | 510 | 506 | 2538 |
Response rate (%) | 24 | 22 | 27 | 22 | 13 | 20 |
a Simple random sample from national population registers.
b Individuals from the simple random sample enriched with telephone numbers.
c Individuals randomly selected from the enriched sample.
b Individuals from the simple random sample enriched with telephone numbers.
c Individuals randomly selected from the enriched sample.
Completed a | 509 | 503 | 510 | 510 | 506 | 2538 |
|---|---|---|---|---|---|---|
Reasons for non-participation | ||||||
Appointment b | 58 | 51 | 345 | 56 | 141 | 651 (7%) |
Callback c | 292 | 434 | 98 | 760 | 424 | 2008 (20%) |
Not in the target group (screened) d | 56 | 70 | 11 | 35 | 75 | 247 (3%) |
Refusal e | 275 | 253 | 113 | 322 | 272 | 1235 (12%) |
Refusal (Black list) f | 1 | 13 | 0 | 20 | 35 | 69 (0.7%) |
Timeout Callback g | 870 | 876 | 776 | 623 | 2077 | 5222 (53%) |
Wrong number h | 73 | 91 | 30 | 21 | 265 | 480 (5%) |
Total non-participation | 1625 | 1788 | 1373 | 1837 | 3289 | 9912 |
a Completed: Interview completed.
b Appointment: Participant was contacted, and a callback was scheduled, however subsequent attempts were unsuccessful.
c Callback: Includes busy line or voicemail. No direct contact was made with the participant.
d Not in target group (screened): Participant did not meet the inclusion criteria due to age, incorrect name or address, or language barriers
e Refusal: Participant declined to participate.
f Refusal (Blacklist): Listed on Norstat’s do-not-contact list after requesting not to be contacted again in a previous Norstat-surve
g Timeout Callback: Maximum number of call attempts was reached without contact.
h Wrong Number: The dialled number was non-existent.
b Appointment: Participant was contacted, and a callback was scheduled, however subsequent attempts were unsuccessful.
c Callback: Includes busy line or voicemail. No direct contact was made with the participant.
d Not in target group (screened): Participant did not meet the inclusion criteria due to age, incorrect name or address, or language barriers
e Refusal: Participant declined to participate.
f Refusal (Blacklist): Listed on Norstat’s do-not-contact list after requesting not to be contacted again in a previous Norstat-surve
g Timeout Callback: Maximum number of call attempts was reached without contact.
h Wrong Number: The dialled number was non-existent.
Characteristics of child participants
Across the Nordic countries, 79% of parents or guardians of participating children completed a telephone interview (CATI), while 21% responded via the online questionnaire (CAWI). The distribution between CATI and CAWI varied across countries, ranging from 90% CATI and 10% CAWI in Iceland, to 71.5% CATI and 28.5% CAWI in Sweden.
The samples of children aged 7–12 years were drawn from national registers based on records as of October 1, 2023. Since data collection started in spring (and in Finland during autumn), the child participants’ actual ages at the time of data collection ranged from 7 to 13 years. 13 year olds were included in the 7–12 year age group in tables and analyses.
In all Nordic countries, more boys than girls participated (53% vs. 47%). Participation was highest among children whose parents or guardians had a high level of education (73%), with country-specific rates ranging from 81% in Denmark to 66% in Iceland. Compared to the general population in each country, boys and children whose parents or guardians had higher levels of education were overrepresented in the survey ( Appendix 4 ). Conversely, girls and children whose parents or guardians had lower levels of education were underrepresented. To account for these discrepancies, survey weights were applied in the different analyses.
Education Group | n=508 | n=503 | n=505 | n=510 | n=503 | n=2529 |
|---|---|---|---|---|---|---|
Low/Medium | 99 (19.5%) | 160 (31.8%) | 170 (33.7%) | 146 (28.6%) | 109 (21.7%) | 684 (27.0%) |
High | 409 (80.5%) | 343 (68.2%) | 335 (66.3%) | 364 (71.4%) | 394 (78.3%) | 1845(73.0%) |
Sex | n=508 | n=503 | n=508 | n=510 | n=505 | n=2534 |
Male | 276 (54.3%) | 272 (54.1%) | 271 (53.3%) | 262 (51.4%) | 263 (52.1%) | 1344(53.0%) |
Female | 232 (45.7%) | 231 (45.9%) | 237 (46.7%) | 248 (48.6%) | 242 (47.9%) | 1190(47.0%) |
Survey method | n=508 | n=503 | n=508 | n=510 | n=505 | n=2534 |
CATI | 407 (80.1%) | 395 (78.5%) | 455 (89.6%) | 380 (74.5%) | 361 (71.5%) | 1998(78.8%) |
CAWI | 101 (19.9%) | 108 (21.5%) | 53 (10.4%) | 130(25.5%) | 144 (28.5%) | 536 (21.2%) |
Strengths and Limitations
The Nordic Monitoring System is the only surveillance system that provides comparable data on healthy and sustainable behaviours, as well as overweight, across the Nordic Region. Other national surveys lack comparability due to differences in survey years, age groups, and methodologies. Its comprehensive dietary data provides unique insights into nutritional status and trends.
A key improvement in the survey 2024 questionnaires is the reduced response time, achieved through shorter and reworded questions and a revised sequence that considers the placement of sensitive items. To accommodate new content, questions of minor relevance were excluded. Data quality was enhanced by using control filters, and inclusivity was improved by incorporating country-specific examples. The revisions also reflect a stronger emphasis on sustainability, with new items on sustainable behaviours, including food choices with varying greenhouse gas (GHG) footprints—such as pulses, meat, and dairy—and low-carbon transportation, such as walking and cycling. Additional questions address weekly alcohol consumption, as well as the use of e-cigarettes and nicotine pouches.
Another strength is the mixed-mode design implemented in 2024, in which an online questionnaire was offered as a secondary option to telephone interviews to enhance response rates (Greene et al., 2008). However, mode effects may affect comparability, as telephone interviews tend to elicit more socially desirable responses on sensitive topics, such as lower reported rates of obesity, smoking and alcohol consumption, and higher reported intake of fruits and vegetables and physical activity (Link and Mokdad 2005; Greene et al., 2008). To enable comparability, the use of online questionnaires was limited to approximately 25%, resulting in 27% among adults and 21% among children.
Despite these strengths, the survey has several important limitations.
First, the overall response rate in survey 2024 was notably low across all countries. This finding is consistent with international trends of declining participation in national surveys, as reported in data from 45 countries (International Social Survey Programme, 2025). To mitigate potential bias introduced by the low response rate and to improve the representativeness of the results, statistical weighting techniques were applied.
A further potential source of selection bias arises from the inclusion criteria: only individuals with a registered phone number were invited to participate. This may limit representativeness relative to the general population, as phone listings do not provide fully random coverage.
Among children, analyses of social inequalities in healthy and sustainable behaviours and overweight were constrained by small subgroup sizes. Because the number of children with parents in the lowest education category was limited, the low and medium parental education groups were combined to allow for reliable statistical comparison.
Seasonal variation in data collection also introduces uncertainty, particularly for indicators with short reference periods. Physical activity data refer to the last seven days, but the timing of data collection differed between survey years. In 2014, all Nordic countries collected data in autumn, whereas in 2024, only Finland did so. Norway and Iceland collected data in spring, while Denmark and Sweden collected data in both spring and summer. These differences may affect time-trend comparability. A scoping review found mixed results, showing either no seasonal effect or higher moderate-to-vigorous physical activity (MVPA) levels in spring compared with autumn (Turrisi et al., 2021), patterns that may extend to walking and cycling. Limited evidence also suggested either no differences or slightly higher sedentary behaviour in spring.
Seasonality may likewise influence alcohol consumption and binge drinking, which are assessed over the last seven days and during the past month, respectively. Both tend to increase during the summer months (Knudsen and Skogen, 2015; Leifman and Gustafsson, 2004). In contrast, dietary assessment is less affected by seasonal variation, as it is based on a 12-month reference period.
The 2024 survey also combined TV and computer screen time into a single question. While this change reflects current technology use, it prevents direct comparison with the 2014 survey data.
References
Greene, J., Speizer, H., & Wiitala, W. (2008). Telephone and web: Mixed-mode challenge. Health Services Research, 43, 230–248. https://doi.org/10.1111/j.1475-6773.2007.00802.x
Knudsen, A. K., & Skogen, J. C. (2015). Monthly variations in self-report of time-specified and typical alcohol use: The Nord-Trøndelag Health Study (HUNT3). BMC Public Health, 15, 172. https://doi.org/10.1186/s12889-015-1526-6
Leifman, H., & Gustafsson, N. K. (2004). Drickandets temporala struktur: Analyser av alkoholkonsumtionens och berusningsdrickandets månatliga variationer i Sverige. Nordic Studies on Alcohol and Drugs, 21(1), 5–30. https://doi.org/10.1177/145507250402100103
Link, M. W., & Mokdad, A. H. (2005). Alternative modes for health surveillance surveys: An experiment with web, mail, and telephone. Epidemiology, 16(5), 701–704. https://doi.org/10.1097/01.ede.0000171271.79172.57
Turrisi, T. B., Bittel, K. M., West, A. B., Hojjatinia, S., Hojjatinia, S., Mama, S. K., Lagoa, C. M., & Conroy, D. E. (2021). Seasons, weather, and device-measured movement behaviours: A scoping review from 2006 to 2020. International Journal of Behavioral Nutrition and Physical Activity, 18, 24. https://doi.org/10.1186/s12966-021-01091-1