Childhood sensorineural hearing loss and adult mental health up to 43 years later: results from the HUNT study.

BACKGROUND: Hearing loss is a global public health problem putting millions of people at risk of experiencing impediments in communication and potentially impaired mental health. Many studies in this field are based on small, cross sectional samples using self-report measures. The present study aims to investigate the association between childhood sensorineural hearing loss and mental health in adult men and women longitudinally in a large cohort with a matched control group, and hearing is measured by pure-tone audiometry. Studies of this kind are virtually non-existing. METHODS: The present study combines data from two large studies; the School Hearing Investigation in Nord-Trøndelag (SHINT) carried out yearly from 1954 to 1986, and the second wave of the Nord-Trøndelag Health Study (HUNT 2) conducted from 1995 to 1997. The participants were 7, 10 or 13 years during the SHINT, and between 20 and 56 years old during HUNT 2. The total sample consisted of 32,456 participants (of which 32,104 in the reference group). Participants with a sensorineural hearing loss in SHINT of 41 dB or more were classified with moderate-severe hearing loss (N = 66), 26-40 dB as mild (N = 66) and 16-25 dB as slight (N = 220). Mental health in adulthood was measured in HUNT 2 by symptoms of anxiety and depression, subjective well-being, and self-esteem. The association between childhood sensorineural hearing loss and adult mental health was tested by means of ANOVA. RESULTS: There was a significant relation between slight childhood sensorineural hearing loss and lowered subjective well-being in women (B = -.25, p = 0.038). Further investigation of the results revealed a significant association between slight hearing loss and symptoms of anxiety and depression (B = .30, p = 0.054) and between mild hearing loss and lowered self-esteem (B = .63, p = 0.024) among women aged 20-39 years. There were no significant relations between childhood sensorineural hearing loss and any of the three mental health outcomes among men. CONCLUSIONS: This study suggests that women with slight or mild sensorineural hearing loss from childhood experience elevated levels of symptoms of anxiety and depression, lowered subjective well-being and lowered self-esteem. However, the results should be interpreted with caution due to a lack of power in some analyses.

The association of high sensitivity C-reactive protein and incident Alzheimer disease in patients 60 years and older: The HUNT study, Norway.

BACKGROUND: With ageing, long-standing inflammation can be destructive, contributing to development of several disorders, among these Alzheimer's disease (AD). C-reactive protein (CRP) is a relatively stable peripheral inflammatory marker, but in previous studies the association between highly sensitive CRP (hsCRP) and AD have shown inconsistent results. This study examines the association between AD and hsCRP in blood samples taken up to 15 years prior to the diagnoses of 52 persons with AD amongst a total of 2150 persons ≥60 years of age. RESULTS: Data from Norway's Nord-Trøndelag Health Study (HUNT 2) and the Health and Memory Study (HMS) were linked. The participants had an average age of 73 years, and diagnosed with AD up to 15 years [mean 8.0 (±3.9)] following hsCRP measurement. Logistic regression models showed an adverse association between hsCRP and AD in participants aged 60-70.5 (odds ratio: 2.37, 95% CI: 1.01-5.58). Conversely, in participants aged 70.6-94, there was an inverse association between hsCRP and AD (odds ratio: 0.39, 95% CI: 0.19-0.84). When applying multivariate models the findings were significant in individuals diagnosed 0.4-7 years after the hsCRP was measured; and attenuated when AD was diagnosed more than seven years following hsCRP measurement. CONCLUSIONS: Our study is in line with previous studies indicating a shift in the association between hsCRP and AD by age: in adults (60-70.5 years) there is an adverse association, while in seniors (>70.6 years) there is an inverse association. If our findings can be replicated, a focus on why a more active peripheral immune response may have a protective role in individuals ≥70 years should be further examined.

Interaction between Parental Education and Twin Correlations for Cognitive Ability in a Norwegian Conscript Sample.

We examine a sample of Norwegian twin conscripts for evidence of an interaction between parental education and the heritability of general cognitive ability (GA). Ability scores were obtained on 1706 pairs of twins who were conscripted into the Norwegian Armed Forces between 1931and 1960. Education scores were available for mothers and fathers; the majority of the parents had less than a high school education. GA scores were heteroscadistic with respect to mid-parent education, with reduced variability at higher levels of education. Both MZ and DZ twin correlations for GA were linearly and negatively related to mid-parent education, DZ twins substantially more so. When the model was extended to an ACE model consisting of standardized positive ACE variance components, the modification appeared to disappear. Further analysis revealed that this occurred because the steep decline of DZ twin correlations with increasing mid-parent education resulted in a violation of the classical twin model for much of the parameter space. Other phenomena that might result in large declines in DZ twin correlations are considered, along with implications for other studies of socioeconomic interactions with the heritability of GA in European samples.

Pre-pregnancy mental distress and musculoskeletal pain and sickness absence during pregnancy - a twin cohort study.

Background: Sickness absence (SA) among pregnant women is high. The aim of this study was to examine whether factors known to predict SA in general also predict SA during pregnancy by estimating the association between prior mental distress and musculoskeletal pain and SA during pregnancy, and to assess the influence of familial (genetic and shared environmental) factors. In this prospective cohort study, data from 2076 female twins born 1967-79 who participated in a questionnaire study in 1998 were linked to register data on SA and childbirth during the years 1998-2008. Baseline measures included mental distress (symptoms of anxiety and depression; SCL-5) and musculoskeletal pain (lumbar spine, neck/shoulder and/or persisting muscular pain). SA was measured as a ratio of days on SA divided by potential working days. Negative binomial regression was performed for individual and within-pair effects. Musculoskeletal pain, but not mental distress, was prospectively associated with overall SA during pregnancy in the adjusted individual-level analyses. With each standard deviation increase in musculoskeletal pain, SA granted for any disorder increased with 12% (IRR 1.12, 95% CI = 1.07-1.17) and SA granted for pregnancy related disorders increased with 9% (IRR 1.09, 95% CI = 1.02-1.17). Within-pair estimates were similar, suggesting little or no familial confounding. Women with previous musculoskeletal pain are at increased risk of SA during pregnancy, whereas no increased risk in women with previous symptoms of mental distress could be demonstrated. SA during pregnancy seems partly to be associated with different factors than SA in general.

Is the twin-singleton difference in BMI related to the difference in birth weight? A register-based birth cohort study of Norwegian males.

OBJECTIVE: The aim was to test the hypothesis that the difference in body mass index (BMI) between twins and singletons may be attributed to a difference in birth weight. METHODS: Data from the Medical Birth Registry of Norway were linked with data from the Norwegian Conscript Service. This study used data on 411,186 males who were born in single or twin births in Norway during 1967 to 1984, and who were examined at the mandatory military conscription (98% were examined the year they turned 18 or 19 years of age). RESULTS: The difference in BMI between singletons and twins was 0.49 kg/m(2) (95% confidence interval [CI]: 0.41, 0.56) after adjustment for background factors and gestational age at birth. When birth weight was added to the model, the difference was reduced to 0.17 kg/m(2) (95% CI: 0.09, 0.25). The corresponding figures for sibships that included both singletons and twins were 0.63 kg/m(2) (95% CI: 0.39, 0.86) and 0.38 kg/m(2) (95% CI: 0.06, 0.70) when twins were compared with their singleton brothers. In both the analysis of the total study population and the analysis of the sibships, birth weight was significantly associated with the BMI after adjustment for twin status, gestational age at birth, and background factors. CONCLUSIONS: Male twins born in Norway during 1967 to 1984 had lower BMI at the military conscription than had singletons, and a part of this difference may probably be attributed to lower intrauterine growth rate among twins. Am. J. Hum. Biol. 28:566-573, 2016. © 2016 Wiley Periodicals, Inc.

Occupational noise exposure and hearing: a systematic review.

PURPOSE: To give a systematic review of the development of noise-induced hearing loss (NIHL) in working life. METHODS: A literature search in MEDLINE, Embase, Web of Science, Scopus, and Health and Safety Abstracts, with appropriate keywords on noise in the workplace and health, revealed 22,413 articles which were screened by six researchers. A total of 698 articles were reviewed in full text and scored with a checklist, and 187 articles were found to be relevant and of sufficient quality for further analysis. RESULTS: Occupational noise exposure causes between 7 and 21 % of the hearing loss among workers, lowest in the industrialized countries, where the incidence is going down, and highest in the developing countries. It is difficult to distinguish between NIHL and age-related hearing loss at an individual level. Most of the hearing loss is age related. Men lose hearing more than women do. Heredity also plays a part. Socioeconomic position, ethnicity and other factors, such as smoking, high blood pressure, diabetes, vibration and chemical substances, may also affect hearing. The use of firearms may be harmful to hearing, whereas most other sources of leisure-time noise seem to be less important. Impulse noise seems to be more deleterious to hearing than continuous noise. Occupational groups at high risk of NIHL are the military, construction workers, agriculture and others with high noise exposure. CONCLUSION: The prevalence of NIHL is declining in most industrialized countries, probably due to preventive measures. Hearing loss is mainly related to increasing age.

Mood, anxiety, and alcohol use disorders and later cause-specific sick leave in young adult employees.

BACKGROUND: Mental disorders strongly influence work capability in young adults, but it is not clear which disorders that are most strongly associated with sick leave, and which diagnoses that are stated on the sick leave certificates. Better knowledge of the impairments associated with different mental disorders is needed for optimal planning of interventions and prioritization of health services. In the current study, we investigate the prospective associations between eight mood, anxiety, and alcohol use disorders, and later sick leave granted for mental, somatic, or any disorder. METHODS: Lifetime mental disorders were assessed by structured diagnostic interviews in 2,178 young adults followed for eight years with registry data on sick leave. Relative risk ratios were estimated for the associations between each mental disorder and the different forms of sick leave. RESULTS: All included diagnoses were associated with later sick leave. In adjusted analyses, major depressive disorder and generalized anxiety disorder were the strongest predictors of sick leave granted for mental disorders, whereas social anxiety disorder and specific phobia were the strongest predictors of sick leave granted for somatic disorders. Specific phobia and major depressive disorder had the highest attributable fractions for all-cause sick leave. CONCLUSIONS: Mood and anxiety disorders constituted independent risk factors for all cause sick leave, whereas alcohol use disorders seemed to be of less importance in young adulthood. Disorders characterised by distress were most strongly associated with sick leave granted for mental disorders, whereas disorders characterised by fear primarily predicted sick leave granted for somatic conditions. A large part of all sick leave is related to specific phobia, due to the high prevalence of this disorder. The impairment associated with this common disorder may be under-acknowledged, and it could decrease work capacity among individuals with somatic disorders. This disorder has good treatment response and may be overlooked as a target for interventions aimed at prevention of sick leave.

Association of psychological distress late in life and dementia-related mortality.

OBJECTIVE: It is not fully understood how subjective feelings of psychological distress prognosticate dementia. Our aim was to investigate the association between self-reported psychological distress and risk of dementia-related mortality. METHOD: We included 31,043 eligible individuals between the ages of 60 and 80 years, at time of examination, from the CONOR (Cohort of Norway) database. They were followed for a period of 17.4 years (mean 11.5 years). The CONOR Mental Health Index, a seven-item self-report scale was used. A cut-off score equal to or above 2.15 on the scale denoted psychological distress. Cox regression was used to assess the association between psychological distress and risk of dementia-related mortality. RESULTS: Total number of registered deaths was 11,762 and 1118 (9.5%) were classified as cases of dementia-related mortality. We found that 2501 individuals (8.1%) had psychological distress, of these, 119 (10.6%) had concomitant dementia-related mortality. Individuals with psychological distress had an increased risk of dementia-related mortality HR = 1.52 (95% confidence interval (CI) 1.25-1.85) after adjusting for age, gender and education. The association remained significant although attenuated when implemented in a full adjusted model, including general health status, smoking, obesity, hypertension, diabetes and history of cardiovascular disease; hazard ratio, HR = 1.30 (95% CI 1.06-1.59). CONCLUSION: Our results indicate that psychological distress in elderly individuals is associated with increased risk of dementia-related mortality. Individuals at increased risk of dementia may benefit from treatments or interventions that lessen psychological distress, but this needs to be confirmed in future clinical studies.

How sociodemographic and hearing related factors were associated with use of hearing aid in a population-based study: The HUNT Study.

BACKGROUND: The purpose was to study hearing aid (HA) use in persons 65 years and older, and to investigate how socioeconomic and hearing related factors were associated to use of HA. METHOD: This study included 11,602 persons (65 years and above) from the second Nord-Trøndelag Health Study (HUNT2) and the integrated North-Trøndelag hearing loss study (NTHLS) in 1995-1997. Audiometry was taken of all participants. Missing information about use of HA in possible users of HA existed in data from 1103 (9.5 %) of the participants. Effects of sociodemographic variables, low, medium and high frequency hearing thresholds and being bothered by their hearing were explored in men and women, adjusting the effects for each other. Cross tabulations and logistic regression analyses were used. RESULTS: In all, 14 % (1472 of 10,499) were users of HA, but 62 % had a mean hearing impairment (HI) based on 0.5, 1, 2, 4 kHz over both ears >25 dB. Use of HA was associated with higher education. Adjusting for all covariates and hearing variables, each 10 dB medium frequency threshold shift increased the chance of HA-use by a factor of two-three in both men and women. Having reported being bothered by hearing loss additionally increased the chance around sevenfold. Low frequency hearing thresholds were not associated with HA-use in women. In men, low frequency hearing thresholds up to 50 dB increased odds for use of HA, but low frequency hearing thresholds ≥ 70 dB decreased odds for use of HA. Men living with a spouse had higher odds for using HA compared to men without a spouse. For women there is no difference between those with and without spouse in use of HA. Men and women without spouse did not differ in their use of HA. CONCLUSIONS: About two third of 65 years and older participants had a HI higher than 25 dB, but only one seventh used HA. Use of HA was associated with higher than basic education. Men without a spouse were less likely to use HA compared to men with a spouse.

Childhood otitis media is associated with dizziness in adulthood: the HUNT cohort study.

The objective of the study was to examine the association between otitis media in childhood and dizziness in adulthood. Longitudinal, population-based cohort study of 21,962 adults (aged 20-59 years, mean 40) who completed a health questionnaire in the Nord-Trøndelag Hearing Loss Study was conducted. At 7, 10 and 13 years of age, the same individuals underwent screening audiometry in a longitudinal school hearing investigation. Children found with hearing loss underwent an ear, nose and throat specialist examination. Adults diagnosed with childhood chronic suppurative otitis media (n = 102) and childhood hearing loss after recurrent acute otitis media (n = 590) were significantly more likely to have increased risk of reported dizziness when compared to adults with normal hearing as children at the school investigation and also a negative history of recurrent otitis media (n = 21,270), p < 0.05. After adjusting for adult age, sex and socio-economic status, the odds ratios were 2.1 [95 % confidence interval (CI): 1.4-3.3] and 1.3 (95 % CI: 1.0-1.5), respectively. This longitudinal cohort study suggests that childhood chronic suppurative otitis media and childhood hearing loss after recurrent acute otitis media are associated with increased risk of dizziness in adulthood. This might reflect a permanent effect of inflammatory mediators or toxins on the vestibular system. The new finding stresses the importance of treatment and prevention of these otitis media conditions.

Childhood sensorineural hearing loss: effects of combined exposure with aging or noise exposure later in life.

The aim of the study was to examine childhood high-frequency sensorineural hearing loss (HF-SNHL) and the effects of combined exposure with aging or noise exposure on HF hearing thresholds in adulthood. Population-based cohort study of 30,003 adults (mean age 40 years) underwent an audiometry and completed a hearing questionnaire. At age 7-13 years, the same people had participated in a longitudinal school hearing investigation, in which 283 participants were diagnosed with HF-SNHL [PTA 3-8 kHz ≥ 25 dB HL (mean 45 dB HL), worse hearing ear], and 29,720 participants had normal hearing thresholds. The effect of childhood HF-SNHL on adult hearing threshold was significantly moderated by age. Age stratified analyses showed that the difference in HF hearing thresholds between adults with and without childhood HF-SNHL was 33 dB (95 % CI 31-34) in young adults (n = 173, aged 20-39 years) and 37 dB (95 % CI 34-39) in middle-aged adults (n = 110, aged 40-56 years). The combined exposure of childhood HF-SNHL and noise exposure showed a simple additive effect. It appears to be a super-additive effect of childhood-onset HF-SNHL and aging on adult hearing thresholds. An explanation might be that already damaged hair cells are more susceptible to age-related degeneration. To exclude possible birth cohort effects, the finding should be confirmed by a study with several audiometries in adulthood.

Coping With Strain (CWS) course - its effects on depressive symptoms: A four-year longitudinal randomized controlled trial.

The Coping With Strain (CWS) course is a modification of the Coping With Depression (CWD) course. CWD is by far the most studied psycho-educational intervention to reduce and prevent depression, but CWD has never been tested in a randomized controlled trial in the workplace. This study seeks to examine the extent to which CWS, on a short-term and a long-term basis, reduces depressive symptoms in employees. After advertising at workplaces, 119 employees were randomized into Intervention Group I (IG1), which immediately participated in CWS, or Intervention Group II (IG2), which functioned as a control group for six months until its participation in CWS. The follow up period lasted for four years in both IG1 and IG2. Linear mixed models were fitted to the data. Depressive symptoms were significantly reduced during the course. The reduction of depressive symptoms was maintained over a period of four years in both IG1 and IG2, although there is a slight increase towards the end of the follow-up period. CWS is effective in reducing depressive symptoms among employees. The effects are long lasting and may be maintained over a period of four years.

Alcohol consumption and risk of dementia up to 27 years later in a large, population-based sample: the HUNT study, Norway.

The relationship between alcohol consumption and dementia risk is unclear. This investigation estimates the association between alcohol consumption reported in a population-based study in the mid-1980s and the risk for dementia up to 27 years later. The entire adult population in one Norwegian county was invited to the Nord-Trøndelag Health Study during 1984-1986 (HUNT1): 88 % participated. The sample used in this study includes HUNT1 participants born between 1905 and 1946 who completed the questionnaire assessing alcohol consumption. A total of 40,435 individuals, of whom 1084 have developed dementia, are included in the analysis adjusted for age, sex, years of education, hypertension, obesity, smoking, and symptoms of depression. When adjusting for age and sex, and compared to reporting consumption of alcohol 1-4 times during the last 14 days (drinking infrequently), both abstaining from alcohol and reporting consumption of alcohol five or more times (drinking frequently) were statistically significantly associated with increased dementia risk with hazard ratios of 1.30 (95 % CI 1.05-1.61) and 1.45 (1.11-1.90), respectively. In the fully adjusted analysis, drinking alcohol frequently was still significantly associated with increased dementia risk with a hazard ratio of 1.40 (1.07-1.84). However, the association between dementia and abstaining from alcohol was no longer significant (1.15, 0.92-1.43). Equivalent results for Alzheimer's disease and vascular dementia indicated the same patterns of associations. When adjusting for other factors associated with dementia, frequent alcohol drinking, but not abstaining from alcohol, is associated with increased dementia risk compared to drinking alcohol infrequently.

Childhood Otitis Media: A Cohort Study With 30-Year Follow-Up of Hearing (The HUNT Study).

OBJECTIVES: To study the extent to which otitis media (OM) in childhood is associated with adult hearing thresholds. Furthermore, to study whether the effects of OM on adult hearing thresholds are moderated by age or noise exposure. DESIGN: Population-based cohort study of 32,786 participants who had their hearing tested by pure-tone audiometry in primary school and again at ages ranging from 20 to 56 years. Three thousand sixty-six children were diagnosed with hearing loss; the remaining sample had normal childhood hearing. RESULTS: Compared with participants with normal childhood hearing, those diagnosed with childhood hearing loss caused by otitis media with effusion (n = 1255), chronic suppurative otitis media (CSOM; n = 108), or hearing loss after recurrent acute otitis media (rAOM; n = 613) had significantly increased adult hearing thresholds in the whole frequency range (2 dB/17-20 dB/7-10 dB, respectively). The effects were adjusted for age, sex, and noise exposure. Children diagnosed with hearing loss after rAOM had somewhat improved hearing thresholds as adults. The effects of CSOM and hearing loss after rAOM on adult hearing thresholds were larger in participants tested in middle adulthood (ages 40 to 56 years) than in those tested in young adulthood (ages 20 to 40 years). Eardrum pathology added a marginally increased risk of adult hearing loss (1-3 dB) in children with otitis media with effusion or hearing loss after rAOM. The study could not reveal significant differences in the effect of self-reported noise exposure on adult hearing thresholds between the groups with OM and the group with normal childhood hearing. CONCLUSIONS: This cohort study indicates that CSOM and rAOM in childhood are associated with adult hearing loss, underlining the importance of optimal treatment in these conditions. It appears that ears with a subsequent hearing loss after OM in childhood age at a faster rate than those without; however this should be confirmed by studies with several follow-up tests through adulthood.

The prevalence of notched audiograms in a cross-sectional study of 12,055 railway workers.

OBJECTIVE: Noise-induced hearing loss (NIHL) is one of the most reported occupational diseases internationally. The occurrence of audiometric notches is emphasized in both American and European guidelines for the diagnosis of NIHL. The aim of this study was to describe the prevalence of notched audiograms among railway personnel with and without noise exposure to better assess the usefulness of such notches in the diagnosis of NIHL. DESIGN: The most recent audiogram from 1994 to 2011 of a total of 12,055 railway workers, age 20 to 65 years, was obtained from the medical records of the occupational health service of the Norwegian State Railways (NSB). The prevalences of three types of notched audiograms, Coles notch, notch index, and 4 kHz notch, were computed, in relation to age, sex, and occupational noise exposure. RESULTS: Coles notch in either ear was found in 63% of the male railway maintenance workers, exposed to noise levels of 75 to 90 dB(A), compared with 53% of the non-noise exposed (<70 dB(A)) traffic controllers (p < 0.001). The corresponding figures for the 4 kHz notch were 31% versus 21% (p < 0.001). For the notch index, 61% of the exposed and 51% of the controls had a notched audiogram (p < 0.001). For female workers, the prevalence of audiometric notches was lower, and the differences between noise exposed and nonexposed was smaller than those in men. Increasing age led to an increased prevalence of notches. CONCLUSIONS: Audiometric notches commonly occur among both noise-exposed and those not exposed to noise in railway personnel. The usefulness of audiometric notches in the diagnosis of NIHL is therefore limited.

Birth weight and the risk of overweight in young men born at term.

OBJECTIVE: The aim of this birth cohort study was to determine the relationship between birth weight and the risk of overweight in young adulthood. METHODS: Data from the Medical Birth Registry of Norway were linked with register data from the National Conscript Service. This study used data on the 348,800 males who were born at term in single births in Norway during 1967 to 1984, and who were examined at the mandatory military conscription (98% were examined the year they turned 18 or 19 years of age). Sibling comparisons were conducted in the 11,865 sibships of two or more full brothers in which at least one brother was overweight (body mass index ≥25.0 kg/m(2) ) and at least one brother was not overweight. RESULTS: When all the men in the study population were compared with each other there was a "J"-shaped association between birth weight and the adjusted odds of overweight. When the men were compared with their brothers, the adjusted odds of overweight increased in an exponential way (linearly in logit) over the entire range of the birth weight scale. A within-family difference of 100 g in birth weight was associated with a within-family difference of 3.5% (99% confidence interval: 2.5-4.6) in the odds of overweight. CONCLUSIONS: There is a positive within-family association between birth weight and the odds of overweight in young Norwegian men born at term.

Mental distress predicts divorce over 16 years: the HUNT study.

BACKGROUND: The association between mental distress and divorce is well established in the literature. Explanations are commonly classified within two different frameworks; social selection (mentally distressed people are selected out of marriage) and social causation (divorce causes mental distress). Despite a relatively large body of literature on this subject, selection effects are somewhat less studied, and research based on data from both spouses is scarce. The purpose of the present study is to investigate selection effects both at the individual level and the couple level. METHODS: The current study is based on couple-level data from a Norwegian representative sample including 20,233 couples. Long-term selection effects were tested for by means of Cox proportional hazard models, using mental distress in both partners at baseline as predictors of divorce the next 16 years. Three identical sets of analyses were run. The first included the total sample, whereas the second and third excluded couples who divorced within the first 4 or 8 years after baseline, respectively. An interaction term between mental distress in husband and in wife was specified and tested. RESULTS: Hazard of divorce was significantly higher in couples with one mentally distressed partner than in couples with no mental distress in all analyses. There was also a significant interaction effect showing that the hazard of divorce for couples with two mentally distressed partners was higher than for couples with one mentally distressed partner, but lower than what could be expected from the combined main effects of two mentally distressed partners. CONCLUSIONS: Our results suggest that mentally distressed individuals are selected out of marriage. We also found support for a couple-level effect in which spouse similarity in mental distress to a certain degree seems to protect against divorce.

Socioeconomic status and sick leave granted for mental and somatic disorders: a prospective study of young adult twins.

BACKGROUND: Low socioeconomic status (SES), indicated by low income and education, has consistently been found to be a strong predictor of sick leave. Several possible pathways from SES to sick leave have been described in previous literature, but there are also evidence indicating that the association can be confounded by common underlying factors. This study utilizes a population-based sample of employed young adult twins to estimate (i) the degree to which education and income are prospectively related to sick leave granted for mental, somatic, and any disorder, and (ii) whether these associations are confounded by familial factors. METHODS: Registry data on educational attainment and income at age 30 and subsequent sick leave were available for 6,103 employed young adult twins, among which there were 2,024 complete twin pairs. The average follow-up time was 6.57 years. Individual-level associations and fixed effects within twin pairs were estimated. RESULTS: Low education and income were associated with sick leave granted for both mental and somatic disorders, and with sick leave granted for any disorder. Associations were attenuated within dizygotic twin pairs and reduced to non-significance within monozygotic twin pairs, suggesting influence of familial factors on the associations between SES and sick leave. CONCLUSIONS: Low SES is associated with a higher level of sick leave granted for both mental and somatic disorders among young adults, but these associations are confounded by factors that are common to co-twins. Education and income are therefore not likely to strongly affect sick leave in young adulthood.

Cardiovascular risk factors and hearing loss: The HUNT study.

OBJECTIVE: The purpose of the present paper was to examine the association between prospectively and cross-sectionally assessed cardiovascular risk factors and hearing loss. DESIGN: Hearing was assessed by pure-tone average thresholds at low (0.25-0.5 kHz), middle (1-2 kHz), and high (3-8 kHz) frequencies. Self-reported or measured cardiovascular risk factors were assessed both 11 years before and simultaneously with the audiometric assessment. Cardiovascular risk factors were smoking, alcohol use, physical inactivity, waist circumference, body mass index, resting heart rate, blood pressure, triglycerides, total serum cholesterol, LDL cholesterol, HDL cholesterol, and diabetes. STUDY SAMPLE: A population-based cohort of 31 547 subjects. RESULTS: After adjustment for age, sex, level of education, income, recurrent ear infections, and noise exposure, risk factors associated with poorer hearing sensitivity were smoking, diabetes, physical inactivity, resting heart rate, and waist circumference. Smoking was only associated with hearing loss at high frequencies. The effects were very small, in combination explaining only 0.2-0.4% of the variance in addition to the component explained by age and the other cofactors. CONCLUSION: This cohort study indicates that, although many cardiovascular risk factors are associated with hearing loss, the effects are small and of doubtful clinical relevance.

Genetic variants in loci 1p13 and 9p21 and fatal coronary heart disease in a Norwegian case-cohort study.

Single nucleotide polymorphisms (SNPs) in loci 1p13 and 9p21 have previously been found to be associated with incident coronary heart disease (CHD). This study aimed to investigate whether these SNPs show associations with fatal CHD in a population-based cohort study after adjustment for socioeconomic- and lifestyle-related CHD risk factors not commonly included in genetic association studies. Using the population-based Cohort of Norway (CONOR), a nested case-cohort study was set up and DNA from 2,953 subjects (829 cases and 2,124 non-cases) were genotyped. The association with fatal CHD was estimated for four SNPs, three from locus 1p13 and one from locus 9p21. Multivariable Cox regression was used to estimate unstratified and gender-stratified hazard ratios while adjusting for major CHD risk factors. The associations between three SNPs from locus 1p13 and non-HDL cholesterol levels were also estimated. Men homozygous for the risk alleles on rs1333049 (9p21) and rs14000 (1p13) were found to have significantly increased hazard ratios in crude and adjusted models, and the hazard ratios remained statistically significant when both genders were analyzed together. Adjustment for additional socioeconomic- and lifestyle-related CHD risk factors influenced the association estimates only slightly. No significant associations were observed between the other two SNPs in loci 1p13 (rs599839 and rs646776) and CHD mortality in either gender. Both rs599839 and rs646776 showed significant, gradual increases in non-HDL cholesterol levels with increasing number of risk alleles. This study confirms the association between 9p21 (rs1333049) and fatal CHD in a Norwegian population-based cohort. The effect was not influenced by several socioeconomic- and lifestyle-related risk factors. Our results show that 1p13 (rs14000) may also be associated with fatal CHD. SNPs at 1p13 (rs599839 and rs646776) were associated with non-HDL cholesterol levels.