Anne Johanne Søgaard

The Oslo Health Study: The impact of self-selection in a large, population-based survey

BackgroundResearch on health equity which mainly utilises population-based surveys, may be hampered by serious selection bias due to a considerable number of invitees declining to participate. Sufficient information from all the non-responders is rarely available to quantify this bias. Predictors of attendance, magnitude and direction of non-response bias in prevalence estimates and association measures, are investigated based on information from all 40 888 invitees to the Oslo Health Study.MethodsThe analyses were based on linkage between public registers in Statistics Norway and the Oslo Health Study, a population-based survey conducted in 2000/2001 inviting all citizens aged 30, 40, 45, 59–60 and 75–76 years. Attendance was 46%. Weighted analyses, logistic regression and sensitivity analyses are performed to evaluate possible selection bias.ResultsThe response rate was positively associated with age, educational attendance, total income, female gender, married, born in a Western county, living in the outer city residential regions and not receiving disability benefit. However, self-rated health, smoking, BMI and mental health (HCSL) in the attendees differed only slightly from estimated prevalence values in the target population when weighted by the inverse of the probability of attendance.Observed values differed only moderately provided that the non-attending individuals differed from those attending by no more than 50%. Even though persons receiving disability benefit had lower attendance, the associations between disability and education, residential region and marital status were found to be unbiased. The association between country of birth and disability benefit was somewhat more evident among attendees.ConclusionsSelf-selection according to sociodemographic variables had little impact on prevalence estimates. As indicated by disability benefit, unhealthy persons attended to a lesser degree than healthy individuals, but social inequality in health by different sociodemographic variables seemed unbiased. If anything we would expect an overestimation of the odds ratio of chronic disease among persons born in non-western countries.

Survival after Hip Fracture: Short- and Long-Term Excess Mortality According to Age and Gender

Abstract: The purpose of this study was to analyze the excess mortality after hip fracture and to reveal whether, and eventually when, the excess mortality vanished in different groups of age and gender. A population-based, prospective, matched-pair, cohort study among persons 50 years of age and older was conducted involving 1338 female and 487 male hip fracture patients with 11 086 and 8141 controls respectively. Occurrence of hip fracture and mortality were recorded from 1986 until 1995. We studied the excess mortality of the hip fracture patients versus controls by using Kaplan–Meier curves and extended Cox regression with hip fracture (yes/no) as time-dependent covariate. The male hip fracture patients had higher mortality than the women the first year after the injury, irrespective of age, both in absolute terms (31% and 17% respectively) and relative to their age-matched controls. The relative risk (RR) of dying within 1 year for hip fracture patients versus controls was 3.3 (95% confidence interval (CI) 2.1–5.2) for women and 4.2 (95% CI 2.8–6.4) for men below 75 years of age. The corresponding figures for persons 85 years and older were 1.6 (95% CI 1.2–2.0) for women and 3.1 (95% CI 2.2–4.2) for men. All groups of age and gender, except women 85 years and older, had a large and significant excess mortality lasting for many years after the hip fracture – at least 5–6 years for women below 75 years of age (RR = 3.2, 95% CI 1.9–5.6). The excess mortality after hip fracture for women 85 years and older had vanished after 3 months (RR = 1.0, 95% CI 0.8–1.1). When referring to the excess mortality after hip fracture it is therefore necessary to specify sex, age and time since injury.

Obesity in Adolescence and Adulthood and the Risk of Adult Mortality

Background: There are few long-term follow-up data on the relation between body mass index (BMI) in adolescence and in adulthood, and between adolescent BMI and adult mortality. The present study explores these relations. Methods: In Norwegian health surveys during 1963–1999, height and weight were measured for 128,121 persons in a standardized way both in adolescence (age 14–19 years) and 10 or more years later. Persons were followed for an average of 9.7 years after the adult measurement. Cox proportional hazard regression models were used to study the association between adolescent and adult BMI and mortality. Results: The odds ratio of obesity (BMI ≥30) in adulthood increased steadily with BMI in adolescence, from 0.2 for low BMI up to 16 for very high BMI. Very high adolescent BMI was associated with 30–40% higher adult mortality compared with medium BMI. Adjusting for adult BMI explained most of the association of adolescent obesity and mortality, especially among men. Adjustment for smoking did not change the results. Conclusions: Obesity in adolescence tends to persist into adulthood. Adolescent obesity is also connected to excess mortality, but this excess seems to be explained mostly by obesity in adulthood. High BMI in adolescence seems to be predictive of both adult obesity and mortality.

Cohort Profile: Cohort of Norway (CONOR)

A number of large population-based cardiovascular surveys have been conducted in Norway since the beginning of the 1970s. The surveys were carried out by the National Health Screening Service in cooperation with the universities and local health authorities. All surveys comprised a common set of questions, standardized anthropometric and blood pressure measurements and non-fasting blood samples that were analysed for serum lipids at the Ulleval Hospital Laboratory. These surveys provided considerable experience in conducting large-scale population-based surveys, thus an important background for the Cohort of Norway (CONOR). In the late 1980s the Research Council of Norway established a programme in epidemiology. This also gave stimulus to the idea of establishing a cohort including both core survey data and stored blood samples. In the early 1990s, all universities, the National Health Screening Service, The National Institute of Public Health and the Cancer Registry discussed the possibility of a national representative cohort. The issue of storing blood samples for future analyses raised some concern and it was discussed in the parliament. In 1994, the Ministry of Health appointed the Steering Committee for the CONOR collaboration. In 1994–95, the fourth round of the Tromso Study was conducted, and became the first survey to provide data and blood samples for CONOR. During the years 1994–2003, a number of health surveys that were carried out in other counties and cities also provided similar data for the network. So far, 10 different surveys have provided data and blood samples for CONOR (Figure 1). The administrative responsibility for CONOR was given to the Norwegian Institute of Public Health (NIPH) in 2002. The CONOR collaboration is currently a research collaboration between the NIPH and the Universities of Bergen, Oslo, Tromso and Trondheim.

The Tromsø Study: Physical Activity and the Incidence of Fractures in a Middle-Aged Population

We have studied the relation of occupational and recreational physical activity to fractures at different locations. All men born between 1925 and 1959 and all women born between 1930 and 1959 in the city of Tromsø were invited to participate in surveys in 1979–1980 and 1986–1987 (The Tromsø Study). Of 16,676 invited persons, 12,270 (73.6%) attended both surveys. All nonvertebral fractures (n = 1435) sustained from 1988 to 1995 were registered in the only hospital in the area. Average age in the middle of the follow‐up period (December 31, 1991) was 47.3 years among men and 45.1 years among women, ranging from 32 to 66 years. Fracture incidence increased with age at all locations among women, but it decreased with or was independent of age among men. Low‐energetic fractures constituted 74.4% of all fractures among women and 55.2% among men. When stratifying by fracture location, the most physically active persons among those 45 years or older suffered fewer fractures in the weight‐bearing skeleton (relative risk [RR] 0.6, confidence interval [CI] 0.4–0.9, age‐adjusted), but not in the non–weight‐bearing skeleton (RR 1.0, CI 0.7–1.2, age‐adjusted) compared with sedentary persons. The relative risk of a low‐energetic fracture in the weight‐bearing skeleton among the most physically active middle‐aged was 0.3 (CI 0.1–0.7) among men and 0.9 (CI 0.4–1.8) among women compared with the sedentary when adjusted for age, body mass index, body height, tobacco smoking, and alcohol and milk consumption. It seems that the beneficial effect on the skeleton of weight‐bearing activity is reflected also in the incidence of fractures at different sites.

Body mass index and mortality: the influence of physical activity and smoking.

PURPOSE To study the association between body mass index (BMI) and mortality, and to evaluate the effect of physical activity during leisure time and smoking on this association in a general male population. METHODS During 1974-1978, all men aged 35-49 yr living in three Norwegian counties were invited to a cardiovascular screening, and 87.1% attended and had their weight and height measured. Men with recognized cardiovascular diseases, diabetes mellitus, or cancer at screening were excluded. The cohort (N = 22,304) was followed for an average of 16.3 yr with respect to total and cause-specific mortality. RESULTS During follow-up, 1909 men died. We found a J-shaped association between BMI and total mortality, and the form of association was similar for death from cardiovascular diseases. Although not statistically significant, a J-shaped association was also suggested in never-smokers. Irrespective of BMI level, ex- and never-smokers had lower mortality than current smokers. Obese smoking men had a relative risk of dying of 2.01 (95% CI: 1.29-3.11) compared with obese never-smokers, and a relative risk of 4.55 (95% CI: 3.34-6.20) compared with normal weight never-smokers (BMI 22-24.9 kg x m(-2)). Within each category of physical activity during leisure time, obese men had a similar increased relative risk of death compared with normal-weight individuals. However, the U- to J-shaped association between BMI and mortality seemed to disappear by increasing level of physical activity, but this finding was not significant. CONCLUSION This study suggests a J-shaped association between BMI and total mortality, also when stratified on smoking habits and physical activity. The suggested linear trend in the most physical active men needs to be reassessed.

Leisure time physical activity in middle age predicts the metabolic syndrome in old age: results of a 28-year follow-up of men in the Oslo study

BackgroundData are scarce on the long term relationship between leisure time physical activity, smoking and development of metabolic syndrome and diabetes. We wanted to investigate the relationship between leisure time physical activity and smoking measured in middle age and the occurrence of the metabolic syndrome and diabetes in men that participated in two cardiovascular screenings of the Oslo Study 28 years apart.MethodsMen residing in Oslo and born in 1923–32 (n = 16 209) were screened for cardiovascular diseases and risk factors in 1972/3. Of the original cohort, those who also lived in same area in 2000 were invited to a repeat screening examination, attended by 6 410 men. The metabolic syndrome was defined according to a modification of the National Cholesterol Education Program criteria. Leisure time physical activity, smoking, educational attendance and the presence of diabetes were self-reported.ResultsLeisure time physical activity decreased between the first and second screening and tracked only moderately between the two time points (Spearmans ρ = 0.25). Leisure time physical activity adjusted for age and educational attendance was a significant predictor of both the metabolic syndrome and diabetes in 2000 (odds ratio for moderately vigorous versus sedentary/light activity was 0.65 [95% CI, 0.54–0.80] for the metabolic syndrome and 0.68 [0.52–0.91] for diabetes) (test for trend P < 0.05). However, when adjusted for more factors measured in 1972/3 including glucose, triglycerides, body mass index, treated hypertension and systolic blood pressure these associations were markedly attenuated. Smoking was associated with the metabolic syndrome but not with diabetes in 2000.ConclusionPhysical activity during leisure recorded in middle age prior to the current waves of obesity and diabetes had an independent predictive association with the presence of the metabolic syndrome but not significantly so with diabetes 28 years later in life, when the subjects were elderly.

What do Norwegian women and men know about osteoporosis

A survey of a random sample of 1514 Norwegian women and men aged 16–79 years was undertaken to investigate knowledge of osteoporosis and attitudes towards methods for preventing this disease. The interviews were carried out by Central Bureau of Statistics of Norway as part of their monthly national poll using a structured questionnaire. Women knew more about osteoporosis than did men (p<01). In both men and women increased knowledge of osteoporosis was correlated to a high level of education. Furthermore it was clearly demonstrated that knowing someone with osteoporosis or suffering from it oneself increased the knowledge of osteoporosis significantly in both women and men. Multiple regression analysis confirmed the univariate analyses, and education was the strongest predictive factor for knowledge. To a hypothetical question as many as two-thirds of the women answered that they would use long-term hormone replacement therapy (HRT) to prevent osteoporosis on the recommendation of their general practitioner. Their attitudes towards the use of estrogen therapy did not show any significant relation to age, but their reluctance towards HRT increased with education (p<001). When asked a question about their preferences regarding the use of physical activity as a means to prevent osteoporosis, older women preferred walking (p<.001), whereas younger women wanted more organized athletic activity (p<001). The data demonstrated that there was a high degree of general knowledge of osteoporosis and its consequences in the general population.

Mental distress and risk of hip fracture. Do broken hearts lead to broken bones

OBJECTIVE: Mental distress may entail increased risk of hip fracture, but it is uncertain whether the effect consists solely of an indirect effect through use of medication, or whether it is also mediated through other mechanism. The purpose of this study was to examine the association between mental distress and risk of hip fracture in women, adjusted for medication (that is, use of tranquillisers/sedatives or hypnotics). DESIGN: A three year follow up of hip fracture was conducted on 18,612 women, consisting of 92.5% of all women aged 50 years or older in a Norwegian county. Three hundred and twenty nine suffered a hip fracture. A mental distress index was based on questions about life dissatisfaction, nervousness, loneliness, sleep disorders, troubled and uneasy feelings, depression and impairment attributable to psychological complaints. Relative risk with 95% confidence intervals (CI) of hip fracture with respect to mental distress were controlled for medication, age, body mass index (BMI), smoking, physical inactivity, and physical illness by means of Cox regression. RESULTS: The 10% of women with the highest mental distress had more than twofold increased risk of hip fracture compared with the 10% of women with the lowest mental distress, after adjustment for age and medication. The relative risk was 1.95 (95% CI 1.2, 3.3) after additional control for BMI, smoking, physical inactivity, and physical illness. The relative risk of hip fracture for daily users of medication compared with never users was 2.1 (95% CI 1.6, 2.9). After adjusting for mental distress it was 1.5 (95% CI 1.0, 2.2). CONCLUSIONS: Risk of hip fracture was positively related to mental distress, also after adjustment for medication use. The effect of tranquillisers/sedatives or hypnotics on hip fracture risk may be overestimated in studies with no adjustments for mental distress.

Mortality following the first hip fracture in Norwegian women and men (1999-2008). A NOREPOS study

Hip fractures are associated with increased mortality and their incidence in Norway is one of the highest worldwide. The aim of this nationwide study was to examine short- and long-term mortality after hip fractures, burden of disease (attributable fraction and potential years of life lost), and time trends in mortality compared to the total Norwegian population. Information on incident hip fractures between 1999 and 2008 in all persons aged 50 years and older was collected from Norwegian hospitals. Death and emigration dates of the hip fracture patients were obtained through 31 December 2010. Standardized mortality ratios (SMRs) were calculated and Poisson regression analyses were used for the estimation of time trends in SMRs. Among the 81,867 patients with a first hip fracture, the 1-year excess mortality was 4.6-fold higher in men, and 2.8-fold higher in women compared to the general population. Although the highest excess mortality was observed during the first two weeks post fracture, the excess risk persisted for twelve years. Mortality rates post hip fracture were higher in men compared to women in all age groups studied. In both genders aged 50 years and older, approximately 5% of the total mortality in the population was related to hip fractures. The largest proportion of the potential life-years lost was in the relatively young-old, i.e. less than 80 years. In men, the 1-year absolute mortality rates post hip fracture declined significantly between 1999 and 2008, by contrast, the mortality in women increased significantly relatively to the population mortality.