Anne Illemann Christensen

Although the Danish National Health Survey (DNHS) uses survey weights to reduce self-selection bias, differences in health status may remain. We explored whether DNHS participants are representative of the general population in Denmark regarding morbidity, particularly mental disorders, and mortality. By individual linkage to administrative registers, we compared DNHS participants ( N = 183,194) with the general population aged 16 years or older ( N = 4,697,047). For 202 health conditions, we estimated period prevalence ratios (PPRs) of having received a diagnosis in the 5 years prior to survey participation and hazard ratios (HRs) of receiving a diagnosis in the subsequent 5 years. Additionally, we estimated mortality HRs, overall and among individuals with prior diagnoses of the specific conditions. Both original weights developed for the DNHS and updated weights better accounting for mental disorders were applied. Overall, weighted survey participants had similar prevalence compared to the general population, but mental disorders were less common before (PPR: 0.86 [0.85; 0.88]) and after (HR: 0.86 [0.84; 0.88]) survey participation. Participants experienced lower all-cause mortality rates than the general population (HR: 0.80 [0.79; 0.82]), especially among those with prior mental disorders (HR: 0.62 [0.59; 0.66]). Applying updated weights resulted in similar mental disorder prevalence (PPR: 0.99 [0.98; 1.01]) but unchanged mortality estimates. The lower mortality among survey participants compared to the general population, especially for individuals with prior mental disorders, suggests that self-selection into participation is not fully accounted for by the original or updated weights. This has implications for the generalisability of DNHS-based analyses.

The National Danish Injury Cohort (NDIC) is a nationwide, register-based cohort established to examine the incidence of total and specific injuries in Denmark and to provide insights into causes and consequences. Comprehensive individual-level information for this cohort is stored in the NDIC dataset, serving as a foundation for analyses of injury determinants and supporting the planning and evaluation of preventive measures aimed at reducing injury-related harm. Individuals registered in the Danish National Patient Register with an injury from 2010 onwards are included in the dataset. Additionally, it comprises persons in the Cause of Death Register whose deaths was attributed to accidents, violence, or suicide. The cohort is currently updated through 2022 and contains information on more than 7.2 million primary injury contacts and 26 thousand accident-related deaths. Analyses based on NDIC demonstrated substantial demographic and geographical disparities in the incidence rates of injuries. Overall, men exhibited higher rates of both injury incidents and injury‑related mortality compared with women. Marked differences were observed when stratifying by sex and age, as well as by region of residence. NDIC offers a solid data foundation facilitating research into injury trends, causes, and impacts, including disparities across social groups and geographic areas. It presents unique opportunities to explore novel research ideas to boost injury prevention, improve targeting of interventions, and reduce health inequalities. Strengthening this research area will help further reinforce NDIC’s role in injury surveillance and evidence‑based policymaking.

Declining response proportions in health surveys may lead to increased non-response bias. Multiple reminders are often used to increase response proportions, and, thus, we aimed to determine if the use of reminders decreased the magnitude of non-response bias among web-mode invited in the Danish National Health Survey 2023. In the Danish National Health Survey 2023, a national random sample of 23 467 individuals (aged ≥16 years) with residence in Denmark were invited by a secure electronic mail service. Invited individuals received up to five inquiries: (i) web invitation, (ii) web reminder, (iii) paper invitation including a questionnaire and a prepaid return envelope, (iv) paper reminder, and (v) paper reminder including a questionnaire and a prepaid return envelope. The cumulative response proportions after first-, second-, third-, fourth-, and fifth inquiries were 19.1%, 28.9%, 37.2%, 39.3%, and 42.0%, respectively. In general, third, fourth, and fifth mailing respondents were more often men, at younger ages, with non-Western backgrounds, and unmarried compared to first mailing respondents. Furthermore, third, fourth, and fifth mailing respondents were in general found to have less favorable health behavior than first mailing respondents, but also a lower prevalence of fair or poor self-rated health and long-standing health problems. In conlusion, reminders are an effective way to increase the response proportion. Furthermore, the use of reminders was found to decrease the magnitude of non-response bias; however, the decrease was small due to the low number of individuals responding after fourth and fifth inquiries.

Background. Ambient air pollution has been associated with exacerbations of chronic obstructive pulmonary disease (COPD) and asthma; however, little is known about indoor environmental factors. Our aim was to study the association between perceived indoor environment and the long-term risk of exacerbations of COPD or asthma. Methods. We followed 2,317 individuals aged ≥16 years with COPD or asthma from the Danish Health and Morbidity Survey from 2000 to 2018. Individuals developing COPD or asthma during the study period were included at the time of incident diagnosis. Individuals were grouped according to their patterns of perceived indoor environment and followed up for exacerbations defined based on information from the Danish National Health Registers. The association between perceived indoor environment and exacerbations was examined using a generalized mixed model with the Poisson distribution of the number of exacerbations and logarithmic transformation of follow-up time as offset. Analyses were adjusted for age, sex, education, household income, smoking, calendar year, construction year, urbanization, home ownership, and resident density. Results. A total of 5,352 exacerbations were recorded in 2,317 individuals during a median of 13.9 years (interquartile range, 7.9–18.2 years). The adjusted incidence rate ratio (IRR) of exacerbations were 1.40 (95% CI 0.85–2.29 and 0.82 (95% CI 0.49–1.38) among individuals with medium and high levels om annoyances, respectively. For annoyances related to temperature and traffic the IRR was 0.88 (95% CI 0.61–1.27) and 1.39 (95% CI 0.88–2.19), respectively. Conclusion. We found no association between indoor environment assessed as annoyances at a single time-point and exacerbations of COPD and asthma.

Declining response proportions in surveys have been observed internationally. Improving response proportions is important for the generalizability of the outcome. The aim of this study was to examine the potential of animation videos to improve response proportions and sample composition in health surveys. A randomized trial was embedded in the Danish National Health Survey 2021 (n = 186,113) where the use of animation videos in the digital invitation letter was tested as a mean to increase response proportion. The effect of both demographic-targeted videos and a general video was tested. The sample was stratified into four subsamples; (1) individuals with non-western background and a non-Danish citizenship (n = 9,956), (2) men aged 16–24 years (n = 12,481), (3) women aged 75 years or older (n = 7,815) and (4) the remaining individuals (n = 155,861). The fourth subsample was randomized into two equal sized groups; a group receiving the general video and a control group receiving no video. Each of the first three subsamples was subsequently randomized into three subgroups with 25% receiving the target group video, 25% receiving the general video and 50% receiving no video. A total of four reminders (one digital and three postal) were sent to the eligible population. The use of animation videos resulted in similar or slightly lower overall response proportion compared to the control group. The different animation videos were found to have heterogeneous effects on response proportions. A positive effect was found among men aged 16–24 years before the delivery of the postal reminder for the targeted animation video compared to no video (odds ratio: 1.13; 95% confidence interval: 1.02–1.26). Overall, the targeted animation videos tended to produce higher response proportions than the general animation video. The heterogeneous effects of the videos suggest that there is some potential for the use of animation videos to improve response proportions and sample composition. The content, target group and timing of evaluation seem to be important for the animation videos to be successful. This warrants further research to better identify in which contexts, in which subgroups and under which circumstances, animation videos are useful to increase response proportions. ClinicalTrials.gov ID: NCT05520242, registered 08/26/2022.

Background: Declining response proportions in surveys have been observed internationally. Improving response proportions is important for the generalizability of the outcome. The aim of this study is to examine the potential of animation videos to improve response proportions and sample composition in health surveys. Methods: A randomized trial was embedded in the Danish National Health Survey 2021 (n=186,113) where the use of animation videos in the digital invitation letter was tested as a mean to increase participation. The effect of both targeted videos and a general video was tested. The sample was randomized into 4 groups; 1) individuals with non-western background and a non-Danish citizenship (n=9,956), 2) men aged 16-24 years (n=12,481), 3) women aged 75 years or older (n=7,815) and 4) the remaining individuals (n=155,861). The 4. group was divided into 2 equal sized groups; a group receiving the general video and a control group receiving no video. Each of the first 3 groups was subsequently divided into 3 subgroups with 25% receiving the target group video, 25% receiving the general video and 50% receiving no video. Results: The use of animation videos resulted in similar or slightly lower response proportions overall compared to the control group. The different animation videos were found to have heterogeneous effects on response proportions. A positive effect was found among men aged 16-24 years before the delivery of the postal reminder for the targeted animation video compared to no video (odds ratio: 1.13; 95% confidence interval: 1.02–1.26). Overall, the targeted animation videos tended to produce higher response proportion than the general animation video. The difference was only statistically significant among young men aged 16-24 years before the delivery of the postal reminder. Conclusions: The heterogeneous effects of the videos suggest that there is some potential for the use of animation videos to improve response proportions and sample composition. The content, target group and timing of evaluation seem to be important for the animation videos to be successful. This warrants further research to better identify in which contexts, in which subgroups and under which circumstances, animation videos are useful to increase response proportions.

The increasing prevalence of reported annoyances in the indoor environment threatens public health. This study aimed to investigate the association between perceived annoyances from the home environment and respiratory infections among individuals with and without asthma or chronic obstructive pulmonary disease (COPD). A total of 16,688 individuals from the Danish Health and Morbidity Survey initiated in 2000 were grouped according to their patterns of perceived annoyances. Information on respiratory infections (all causes, bacterial, viral, and those leading to hospital admissions) was obtained from Danish registers up to 19 years after the survey. Poisson regression of incidence rates (IRs) was applied to estimate incidence rate ratios (IRRs). Annoyances significantly increased the IR for respiratory infections of all causes and bacterial respiratory infections in individuals without asthma or COPD, adjusted IRR 1.16 (95% CI: 1.01, 1.34) and 1.15 (95% CI: 1.02, 1.31), respectively. However, no difference was observed for viral respiratory infections nor hospital admissions. Individuals with asthma or COPD and a high level of annoyances had a non-significantly increased IR in all four analyses of respiratory infections. These findings provide support for perceived annoyances as an important risk factor for respiratory infections.

(1) Background: In December 2020, a broad majority of political parties in Denmark agreed on a new tobacco control act. In addition, price increases on tobacco in 2020 and 2022 became part of the Danish Finance Act. This study protocol describes the study “§SMOKE–A Study of Tobacco, Behavior, and Regulations” designed to monitor and evaluate the implementation and effect of the new strengthened tobacco control acts. The overall aim is to monitor tobacco use among young people before, during, and after implementation of the new tobacco control legislation, including an increased price on tobacco, a ban on point-of-sale tobacco displays, and plain packaging. Subgoals are to monitor overall use of nicotine products, attitudes, and norms. (2) Methods: This study is designed as a five-year impact evaluation with repeated cross-sectional survey data collections. The baseline survey was conducted before implementing an increased price on tobacco, the first step in the new legislation, initiated 1 April 2020. Study participants (n = 37,500) were a random sample of individuals living in Denmark aged 15 to 29 years. (3) Conclusions: This study examines the impact of the new strengthened tobacco control legislation in Denmark from 2020 to 2025. The findings of this study are relevant to other countries facing implementation of similar measures to explore intended and unintended consequences of the legislation and help to identify how the legislation could be further improved.