How should recruitment to public health surveys be conducted? / Hvordan bør rekrutteringen til folkehelseundersøkelsene gjennomføres?

BACKGROUND: The aim of the public health survey in the Norwegian counties is to obtain information that is useful for public health work. In 2018, two parallel data collection processes were undertaken in Hordaland county. Both samples were drawn randomly from the National Population Register, but one of these was limited to users of the helsenorge.no website. The purpose of this article is to investigate the degree to which limiting users to the helsenorge.no website leads to selection bias beyond the selection that occurs through ordinary non-participation. MATERIAL AND METHOD: Services for Sensitive Data (TSD) was used in the data collection for the sample drawn from the National Population Register (n = 36 000), and the helsenorge.no platform was used in the data collection for the sample limited to users of helsenorge.no (n = 30 000). The response rate was 40.8 % and 41.5 %, respectively. RESULTS: For some outcome measures, the differences between the two datasets were modest (gender distribution, age, education and health habits). For variables that were more directly related to health, the differences were greater. In the helsenorge.no sample a higher proportion reported generally poorer health (29.4 vs. 24.0 %), mental health problems (13.6 vs. 11.6 %), disability pension (10.5 vs. 7.8 %) and long-term illness (13.3 vs. 9.3 %). Analyses of subgroups showed more pronounced differences in the proportion with generally poorer health and mental health problems between those with low education in the helsenorge.no sample and the corresponding group in the sample from the National Population Register. INTERPRETATION: Systematic and pronounced differences between the samples show that limiting recruitment to users of helsenorge.no's services results in further selection problems.

Parental socioeconomic status and risk of cerebral palsy in the child: evidence from two Nordic population-based cohorts.

Background: We investigated whether the risk of cerebral palsy (CP) in the child varies by parents' socioeconomic status, in Denmark and Norway. Methods: We included almost 1.3 million children born in Demark during 1981-2007 and 2.4 million children born in Norway during 1967-2007, registered in the Medical Birth registries. Data on births were linked to Statistics Denmark and Norway to retrieve information on parents' education and relationship status and, in Denmark, also income. CP diagnoses were obtained from linkage with national registries. We used multivariate log-binominal regression models to estimate relative risk (RR) of CP according to parental socioeconomic status. Results: There was a strong trend of decreasing risk of CP with additional education of both the mother and the father. These trends were nearly identical for the two parents, with a one-third reduction in risk for those with the highest education compared with parents with the lowest education. When both parents had high education, risk of CP was further reduced (RR 0.58, 0.53-0.63). Women with partners had a reduction in risk (RR 0.79, 0.74-0.85) compared with single mothers overall. Risk patterns were stable over time, across countries and within spastic bilateral and unilateral CP. Household income was not associated with risk of CP. Conclusions: Risk of CP in two Scandinavian countries was lower among educated parents and mothers with a partner, but unrelated to income. Factors underlying this stable association with education are unknown, but could include differences in potentially modifiable lifestyle factors and health behaviours.

Socio-Economic Status and Reproduction among Adults Born with an Oral Cleft: A Population-Based Cohort Study in Norway.

BACKGROUND: It has been reported that people born with orofacial clefts do worse in life than their peers regarding a range of social markers, such as academic achievement and reproduction. We have compared otherwise healthy individuals with and without clefts, to investigate if these differences are due to the cleft or other background factors. MATERIALS AND METHODS: In a retrospective national cohort study, based on compulsory registers with data collected prospectively, we included everybody born in Norway between 1967 and 1992 (1490279 individuals, 2584 with clefts). This cohort was followed until the year 2010, when the youngest individuals were 18 years old. In order to ensure that the individuals were not affected by unknown syndromes or diseases, we excluded all individuals with any chronic medical condition, or who had other birth defects than clefts, hydroceles and dislocated hips. Individuals with oral clefts who were included in the study are said to have isolated clefts. RESULTS: Isolated cleft patients are similar to the general population regarding education, income and social class. Isolated cleft patients have lower fertility than the background population, but considering only married couples this difference in fertility disappeared. CONCLUSIONS: An oral cleft did not appear to affect future socioeconomic status or chances of becoming a parent for children born in Norway. An exception was males with cleft lip and palate, but differences were small.

Economic independence in survivors of cancer diagnosed at a young age: A Norwegian national cohort study.

BACKGROUND: The impact of cancer on socioeconomic outcomes is attracting attention as the number of survivors of cancer in young age continues to rise. This study examines economic independence in a national cohort of survivors of cancer at a young age in Norway. METHODS: Through the linkage of several national registries, the study cohort comprised 1,212,013 individuals born in Norway during 1965 through 1985, of which 5440 had received a cancer diagnosis before age 25 years. Follow-up was through 2007, and the main outcomes were receipt of governmental financial assistance, employment, income, and occupation. Analytic methods included Cox proportional hazard regression, log-binomial regression, and quantile regression models. RESULTS: Individuals in the cancer survivor group had an increased probability of receiving governmental financial assistance (men: hazard ratio [HR], 1.4; 95% confidence interval [CI], 1.3-1.5; women: HR, 1.5; 95% CI, 1.3-1.6) and of not being employed (men: HR, 1.4; 95% CI, 1.2-1.7; women: HR, 1.4; 95% CI, 1.2-1.6) compared with those in the noncancer group. Income discrepancies were particularly pronounced for survivors of central nervous system tumors. There was no difference in representation in higher skilled occupations. CONCLUSIONS: Survivors of cancer at a young age in Norway had an increased risk of being economically dependent and unemployed. This was evident in several tumor groups and was most pronounced in female survivors. There were only small differences in income or representation in higher skilled occupations for most employed survivors compared with the noncancer group. The current results are important for understanding the impact of a cancer diagnosis at a young age on subsequent job market outcomes. Cancer 2016;122:3873-3882. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.

Factors associated with prenatal folic acid and iron supplementation among 21,889 pregnant women in Northern Tanzania: a cross-sectional hospital-based study.

BACKGROUND: Folate and iron deficiency during pregnancy are risk factors for anaemia, preterm delivery, and low birth weight, and may contribute to poor neonatal health and increased maternal mortality. The World Health Organization recommends supplementation of folic acid (FA) and iron for all pregnant women at risk of malnutrition to prevent anaemia. We assessed the use of prenatal folic acid and iron supplementation among women in a geographical area with a high prevalence of anaemia, in relation to socio-demographic, morbidity and health services utilization factors. METHODS: We analysed a cohort of 21,889 women who delivered at Kilimanjaro Christian Medical Centre (KCMC), Moshi, Tanzania, between 1999 and 2008. Logistic regression models were used to describe patterns of reported intake of prenatal FA and iron supplements. RESULTS: Prenatal intake of FA and iron supplements was reported by 17.2% and 22.3% of pregnant women, respectively. Sixteen percent of women reported intake of both FA and iron. Factors positively associated with FA supplementation were advanced maternal age (OR = 1.17, 1.02-1.34), unknown HIV status (OR = 1.54, 1.42-1.67), a diagnosis of anaemia during pregnancy (OR = 12.03, 9.66-14.98) and indicators of lower socioeconomic status. Women were less likely to take these supplements if they reported having had a malaria episode before (OR = 0.57, 0.53-0.62) or during pregnancy (OR = 0.45, 0.41-0.51), reported having contracted other infectious diseases (OR = 0.45, 0.42-0.49), were multiparous (OR = 0.73, 0.66-0.80), had preeclampsia/eclampsia (OR = 0.48, 0.38-0.61), or other diseases (OR = 0.55, 0.44-0.69) during pregnancy. Similar patterns of association emerged when iron supplementation alone and supplementation with both iron and FA were evaluated. CONCLUSIONS: FA and iron supplementation are low among pregnant women in Northern Tanzania, in particular among women with co-morbidities before or during pregnancy. Attempts should be made to increase supplementation both in general and among women with pregnancy complications.

Long-term medical and social consequences of preterm birth.

BACKGROUND: Advances in perinatal care have increased the number of premature babies who survive. There are concerns, however, about the ability of these children to cope with the demands of adulthood. METHODS: We linked compulsory national registries in Norway to identify children of different gestational-age categories who were born between 1967 and 1983 and to follow them through 2003 in order to document medical disabilities and outcomes reflecting social performance. RESULTS: The study included 903,402 infants who were born alive and without congenital anomalies (1822 born at 23 to 27 weeks of gestation, 2805 at 28 to 30 weeks, 7424 at 31 to 33 weeks, 32,945 at 34 to 36 weeks, and 858,406 at 37 weeks or later). The proportions of infants who survived and were followed to adult life were 17.8%, 57.3%, 85.7%, 94.6%, and 96.5%, respectively. Among the survivors, the prevalence of having cerebral palsy was 0.1% for those born at term versus 9.1% for those born at 23 to 27 weeks of gestation (relative risk for birth at 23 to 27 weeks of gestation, 78.9; 95% confidence interval [CI], 56.5 to 110.0); the prevalence of having mental retardation, 0.4% versus 4.4% (relative risk, 10.3; 95% CI, 6.2 to 17.2); and the prevalence of receiving a disability pension, 1.7% versus 10.6% (relative risk, 7.5; 95% CI, 5.5 to 10.0). Among those who did not have medical disabilities, the gestational age at birth was associated with the education level attained, income, receipt of Social Security benefits, and the establishment of a family, but not with rates of unemployment or criminal activity. CONCLUSIONS: In this cohort of people in Norway who were born between 1967 and 1983, the risks of medical and social disabilities in adulthood increased with decreasing gestational age at birth.

Completeness of registration of oral clefts in a medical birth registry: a population-based study.

BACKGROUND: Epidemiological surveillance and research on birth defects require accurate diagnosis and adequate registration. In this regard, the performance of national birth registries is not well described. METHODS: We linked clinical data from all 3,616 cleft cases treated in Norway between 1967 and 1998 with data from the Medical Birth Registry of Norway, and calculated the proportion of clinically verified cases reported to the Registry, stratified by severity. RESULTS: The cleft type most completely ascertained was cleft lip and palate (CLP), of which 94% were reported. Ascertainment was less complete for cleft lip alone (83% recorded), and cleft palate only (CPO) (57% recorded). For each of the three types of clefts, completeness of reporting depended on severity of the cleft. For example, 71% of cases with severe CPO were reported, while only 11% of cases with mild CPO were reported. CONCLUSIONS: Ascertainment was strongly related to cleft type and severity. To the degree that severity of birth defects may be related to their cause, these patterns of registration have implications for surveillance of birth defects as well as the conduct of etiologic studies. The large proportion of cleft palate cases unrecorded at birth suggests that clinical examination of the newborn palate is often inadequate.