Nordic adolescents responding to demanding survey scales in boring contexts: Examining straightlining.

INTRODUCTION: Straightlining, or identical responses across all items within a multi-item scale, is often taken as an indication that responses to all items in a questionnaire are of poor quality. The purpose of this study was to examine straightlining on two scales: The Sense of Unity Scale (SUS) and the short version of the Warwick-Edinburgh Mental Well-being Scale (SWEMWBS). METHODS: Data stem from the 2017-2018 data collections in four Nordic countries of the Health Behaviour in School-children study (HBSC) (15-year-old students only; 50.9% girls; n = 5928). Data were weighted to adjust for oversampling of Swedish-speaking Finnish students and to equalize sample size across countries. The main analyses were done with general linear modeling with adjustments for cluster effects (school classes). RESULTS: The proportion with straightlining on SUS was 22.8%, varying from 5.8% among Swedish girls to 46.4% among Finnish boys. The proportion with straightlining on SWEMWBS was 18.4%, varying from 5.2% among Norwegian girls to 46.0% among Finnish boys. Straightlining on one of the scales correlated with straightlining on the other one. Straightlining tended to inflate Cronbach's α values and reduce number of factors in factor analyses. Associations between the two scales and external variables tended to be lower among straightlining students. Associations between external variables (other than SUS/SWEMWBS) are on average slightly weaker among straightliners. Straightlining students obtained more favorable scores on several resource-related variables. CONCLUSION: Although some problems have been identified, straightlining does not serve well as a general indicator of poor data quality.

Cyberbullying and traditional bullying among Nordic adolescents and their impact on life satisfaction.

Aims: The aim of this study was to investigate the prevalence of cybervictimization in the six Nordic countries and to assess its overlap with traditional bullying. A further aim was to examine potential associations between life satisfaction, on the one hand, and traditional bullying and cyberbullying on the other. Methods: Analyses were based on data from the 2013/2014 Health Behaviour in School-aged Children study. It included 32,210 boys and girls, aged 11, 13, and 15, living in the six Nordic countries. Results: The prevalence of cyberbullying by both pictures and by messages was around 2% in all the Nordic countries except Greenland. There it was considerably higher. The prevalence of being bullied in a traditional manner varied widely by country. For boys, this type of bullying was most frequent in the youngest age group and then decreased steadily in the older age groups. Girls were on average more likely to be cyberbullied. Cyberbullying was more common among 13- and 15-year-olds than 11-year-olds. Higher family affluence was unrelated to the risk of cyberbullying. However, it was related to traditional bullying and combined forms of bullying. Compared with intact families, cybervictimization was commoner among single-parent families and stepfamilies. Adjusting for age, gender, family affluence, and family structure, those subjected to cyberbullying had lower life satisfaction than those who were not bullied. Conclusions: We found relatively little overlap between cyberbullying and traditional bullying, indicating that the two may be separate phenomena stemming from different mechanisms, at least in the Nordic context.

Sexual orientation and migration intentions among rural, exurban and urban adolescents in Iceland.

Rural areas have often been assumed to be somewhat hostile territory for sexual minorities. As a result, moving to an urban area may be an integral part of "coming out" for those living in a rural area. However, surprisingly few quantitative studies have examined the level of rural-to-urban migration intent among sexual minorities. In this study, we examined the migration expectations of adolescents in Iceland, a country characterised by a heavy urban concentration and a scattered rural population, strong international ties and comparatively high levels of formal rights and public acceptance of sexual minorities. Based on a population sample of 2,858 students aged 15-16 years, we found no evidence of greater overall migration expectations among rural or exurban lesbian, gay, bisexual and questioning (LGBQ) youth than their urban counterparts. However, while urban LGBQ youth were more likely to move abroad, young people in other areas are more likely to move domestically. The results are discussed in the context of prior studies of sexual minorities in rural areas and migration expectations among rural youth.

Social inequalities in self-rated health: A comparative cross-national study among 32,560 Nordic adolescents.

AIMS: We aimed to estimate the magnitude of socioeconomic inequality in self-rated health among Nordic adolescents (aged 11, 13 and 15 years) using the Family Affluence Scale (a composite measure of material assets) and perceived family wealth as indicators of socioeconomic status. METHODS: Data were collected from the Health Behaviour in School-aged Children (HBSC) survey in 2013-2014. A sample of 32,560 adolescents from Denmark, Norway, Finland, Iceland, Greenland and Sweden was included in the study. Age-adjusted regression analyses were used to estimate associations between fair or poor self-rated health and the ridit scores for family affluence and perceived wealth. RESULTS: The pooled relative index of inequality of 2.10 indicates that the risk of fair or poor health was about twice as high for young people with the lowest family affluence relative to those with the highest family affluence. The relative index of inequality for observed family affluence was highest in Denmark and lowest in Norway. For perceived family wealth, the pooled relative index of inequality of 3.99 indicates that the risk of fair or poor health was about four times as high for young people with the lowest perceived family wealth relative to those with the highest perceived family wealth. The relative index of inequality for perceived family wealth was highest in Iceland and lowest in Greenland. CONCLUSIONS: Social inequality in self-rated health among adolescents was found to be robust across subjective and objective indicators of family affluence in the Nordic welfare states.

Sexual orientation among Icelandic year 10 adolescents: Changes in health and life satisfaction from 2006 to 2014.

Minority sexual orientation may add additional stresses to the period of adolescence thus affecting mental health and wellbeing. The whole population of year 10 students in 2006, 2010, and 2014 in Iceland were surveyed as part of the Health Behaviour in School-aged Children Survey. Sexual orientation could be identified in 1,994 participants from 2006 (43.8% of population; 988 girls), 3,777 from 2010 (78.6%; 1,863 girls) and 3,526 in 2014 (80.1%; 1,731 girls). About 3.1%, 3.6%, and 4.4% were identified as lesbian, gay, or bisexual (LGB) in 2006, 2010, and 2014, respectively. Given the sampling proportions, the results reflect parameters (population values) rather than statistics (sample values). LGB adolescents were worse off across most of the psychosocial measures across the three surveys as compared with adolescents of unknown sexual orientation (USO). However, the gap between LGB and USO adolescents appears to be closing, at least for the 2010 to 2014 change, suggesting that outcomes for LGB adolescents have improved compared to four years earlier. Social support, liking school and one's classmates, being bullied, and physical and mental health all seem to play an important part in life satisfaction and general wellbeing. While advances have been made for LGB adolescents, gaps between LGB and USO adolescents still exist and need to be closed through evidence-based school and society-wide programs.

Suicidal risk and sexual orientation in adolescence: a population-based study in Iceland.

AIM: Suicidality is an important public health problem, particularly among lesbian, gay, and bisexual (LGB) adolescents and young adults. The purpose of the present study is to compare the rate of suicide ideations and attempts among LGB adolescent to that of non-LGB adolescents in a population-based sample, and to identify important protective factors as well as risk factors Method: We used the Icelandic data set from the 2009/2010 Health Behaviour in School-aged Children (HBSC) study. The sample consisted of 3813 grade 10 Icelandic adolescents; 1876 girls and 1937 boys. The participants were asked about attraction and/or activity, as well as about suicidal ideation and/or attempts. The questionnaire also included various other items regarding health and lifestyle. RESULTS: LGB adolescents were five to six times more likely to have had frequent suicidal ideations. Factors that were associated with less suicide ideations and fewer attempts were easy communication and liking school. The LGB girls were six times more likely to have had frequent suicide attempts, whilst the LGB boys were 17 times more likely to have attempted suicide that often. No specific protective or risk factors were identified for suicidality in LGB adolescents other than bullying. CONCLUSIONS: Adolescents that had engaged in heterosexual activity and those that had LGB attraction had similarly heightened risk for suicidality, but sexually active LGB adolescents were far more likely to have suicidal ideations or to have attempted suicide.

Gender differences in development of mental well-being from adolescence to young adulthood: an eight-year follow-up study.

BACKGROUND: The transition from adolescence to young adulthood is marked by many changes. Mental well-being plays an important role in how individuals deal with these changes and how they develop their lifestyle. The goal of this study was to examine gender differences in the long-term development of self-esteem and other mental well-being variables from the age of 15 to the age of 23. METHODS: A baseline measurement was performed in a nationwide sample of 385 Icelandic adolescents aged 15, and a follow-up measurement was conducted eight years later, when participants had reached the age of 23. Standardized questionnaires were used to measure self-reports of self-esteem, life satisfaction, body image, anxiety, depression and somatic complaints. RESULTS: Women improved their self-esteem significantly more than men from the age of 15 to 23 (p=0.004). Women were more satisfied with their life than men at the age of 23 (p=0.009). Men had a better body image, less anxiety, less depression and fewer somatic complaints than women, independent of age. Across gender, anxiety declined and somatic complaints became fewer (p<0.05). CONCLUSIONS These findings suggest that gender differences in mental well-being factors, favouring men, found in adolescents, are not as long-lasting as previously thought. Women improve their mental well-being from adolescence to young adulthood while men's mental well-being does not change.

Changes in co-use of alcohol and cannabis among Nordic adolescents in the 21st century: Results from the European School Survey Project on Alcohol and Other Drugs study.

INTRODUCTION: In the 21st century, there has been a decline in alcohol use among adolescents in most Nordic countries, while trends of cannabis use have diverged. We explore how alcohol and cannabis use, respectively, and co-use of the two substances, have changed among Nordic adolescents. Three hypotheses are used to frame the study: (i) cannabis use has substituted alcohol use; (ii) there has been a parallel decline in both substances; and/or (iii) there has been a 'hardening' of users, implying that alcohol users increasingly use cannabis. METHODS: Data from the European School Survey Project on Alcohol and Other Drugs, conducted among 15- to 16-year-olds in Denmark, Finland, Iceland, Norway and Sweden (N = 74,700, 49% boys), were used to explore trends of past-year alcohol and cannabis use in the period 2003-2019. RESULTS: The proportion of adolescents reporting alcohol use decreased significantly in all Nordic countries except Denmark. The proportion of those using cannabis only was low (0.0%-0.7%) and stable in all countries. The total number of substance use occasions declined among all adolescents in all countries but Denmark. Among alcohol users, cannabis use became increasingly prevalent in all countries but Denmark. DISCUSSION AND CONCLUSIONS: We found no support for the 'parallel decline hypothesis' in alcohol and cannabis use among Nordic adolescents. Partially in line with the 'substitution hypothesis', cannabis use accounted for an increasing proportion of all substance use occasions. Our results suggests that the co-use of alcohol and cannabis has become more common, thus also providing support to the 'hardening' hypothesis.

Prevalence of age-related macular degeneration in old persons: Age, Gene/environment Susceptibility Reykjavik Study.

PURPOSE: To describe the prevalence and signs of early and late age-related macular degeneration (AMD) in an old cohort. DESIGN: Population-based cohort study. PARTICIPANTS: We included 5272 persons aged ≥66 years, randomly sampled from the Reykjavik area. METHODS: Fundus images were taken through dilated pupils using a 45-degree digital camera and graded for drusen size, type, area, increased retinal pigment, retinal pigment epithelial depigmentation, neovascular lesions, and geographic atrophy (GA) using the modified Wisconsin Age-Related Maculopathy Grading System. MAIN OUTCOME MEASURES: Age-related macular degeneration in an elderly cohort. RESULTS: The mean age of participants was 76 years. The prevalence of early AMD was 12.4% (95% confidence interval [CI], 11.0-13.9) for those aged 66 to 74 years and 36% (95% CI, 30.9-41.1) for those aged ≥85 years. The prevalence of exudative AMD was 3.3% (95% CI, 2.8-3.8). The prevalence of pure GA was 2.4% (95% CI, 2.0-2.8). The highest prevalence of late AMD was among those aged ≥85 years: 11.4% (95% CI, 8.2-14.5) for exudative AMD and 7.6% (95% CI, 4.8-10.4) for pure GA. CONCLUSIONS: Persons aged ≥85 years have a 10-fold higher prevalence of late AMD than those aged 70 to 74 years. The high prevalence of late AMD in the oldest age group and expected increase of elderly people in the western world in coming years call for improved preventive measures and novel treatments.

The Effects of Gender and Family Wealth on Sexual Abuse of Adolescents.

Background: Sexual abuse and sexual assaults against adolescents are among the most significant threats to their health and well-being. Some studies have found poverty to be a risk factor for sexual abuse. The present study investigates the effects of gender and family affluence on the prevalence of sexual abuse of 15-year-old Icelanders in the 10th grade. Methods: The study is based on data collected for the Icelandic part of the Health Behaviour in School-aged Children study in 2014. Standardized questionnaires were sent to all students in the 10th grade in Iceland, of which 3618 participated (85% of all registered students in this grade). Results: Girls were more than twice as likely to be sexually abused as boys (20.2% versus 9.1%). Adolescents perceiving their families to be less well off than others were twice as likely to report sexual abuse as those of ample or medium family affluence. However, family affluence had more effect on the prevalence of abuse in girls than in boys. Conclusion: Female gender and low socioeconomic status may independently contribute to the risk of sexual abuse.

The Problem with Low-Prevalence of Bullying.

This paper tests the hypothesis of whether being bullied in an environment where bullying is infrequent decreases adolescents' life satisfaction. Analyses were based on the international standard questionnaire from the 2005/2006 Health Behaviour in School-aged Children study (HBSC). The sample included answers from 183,736 children in 35 Western, industrialized countries. Our results show that the negative effects of being bullied on the life satisfaction of individuals are stronger in schools and countries where bullying is less frequent. We therefore conclude that the prevalence of bullying in the students' surroundings may act as a mediating variable explaining the relationship between bullying and life satisfaction.

Adolescent alcohol and cannabis use in Iceland 1995-2015.

INTRODUCTION: Over the past two decades, alcohol consumption of Icelandic adolescents has decreased dramatically. The aim of this study was to quantify the extent of this reduction and compare it with the trend in cannabis use over a 20 year period and to identify possible explanations. METHODS: We used data from the Icelandic participants to the European School Survey Project on Alcohol and Other Drugs study (collected via paper-and-pencil questionnaires in classrooms). The sample included all students in the 10th grade (54-89% response rate). RESULTS: The percentage of participants who had never used alcohol during their lifetime rose from 20.8% in 1995 to 65.5% in 2015. Similarly, there was a decline in the proportion of students who had consumed alcohol 40 times or more, from 13.7% to 2.8%. During the same period, the number of students who had never used cannabis rose from 90.2% to 92.0%. In contrast, we found a small, but statistically significant, increase in the prevalence of those who had used cannabis 40 times or more, from 0.7% in 1995 to 2.3% in 2015. Parental monitoring increased markedly between 1995 and 2015, but availability of alcohol decreased. Perceived access to cannabis and youth attitudes towards substance use remained unchanged. DISCUSSION: Although Iceland has enjoyed success in lowering alcohol use among adolescents over the past decades, and somewhat fewer claim to have ever tried cannabis, there has been a threefold increase among heavy users of cannabis. Increased parental monitoring and decreased availability of alcohol explain some of the changes seen.

Pseudoexfoliation in the Reykjavik Eye Study: prevalence and related ophthalmological variables.

PURPOSE: To examine the age and sex-specific prevalence of pseudoexfoliation syndrome (PEX) and its relationship with some ophthalmological variables. METHODS: We carried out a population-based study using a random sample taken from the national population census for citizens of Reykjavik, aged > or = 50 years. A total of 1045 individuals participated in all parts of the study. Pseudoexfoliation was established by slit-lamp examination with a maximally dilated pupil carried out by two experienced ophthalmologists, who were masked to one another's results except in cases of disagreement where they had to reach a consensus. RESULTS: In all, 108 (10.7%) persons were found to have PEX in at least one eye. Prevalence increased from 2.5% in those aged 50-59 years to 40.6% in those aged > or = 80 years. Women were more frequently affected than men (12.3% versus 8.7%). This difference remained statistically significant after controlling for the effect of age (p < 0.001). Eyes with PEX were found to have higher intraocular pressure (IOP) than eyes without PEX (p < 0.05). However, PEX was not found to be related to central corneal thickness, anterior chamber depth, lens thickness, nuclear lens opacifications or optic disc morphology in a multivariate model. CONCLUSIONS: Pseudoexfoliation is an age-related phenomenon commonly found in Iceland. It is more commonly found in women than in men and is associated with elevated IOP.

[The diversion of prescribed stimulant medications of 10th graders in Iceland].

INTRODUCTION: ADHD is a neurodevelopmental disorder that usually surfaces before seven years of age. Stimulants are commonly used medications for the treatment of this disorder in Iceland, but they carry with them a significant risk of both abuse and diversion - i.e. when it is used by an individual other than it was prescribed for by a physician. The purpose of this study was to estimate the prevalence of diversion amongst Icelandic adolescents. MATERIAL AND METHODS: This study is based on data collected in the Icelandic portion of the European School Survey Project on Alcohol and Other Drugs (ESPAD) focused on the drug and alcohol use of 10th graders in Europe. RESULTS: Of the 2,306 students that participated in the study 91% (2,098) claimed they had never been prescribed stimulant medications while 9% (208) claimed they had. Boys were twice as likely to get a stimulant prescription compared to girls. Almost 18% of the participants that had been prescribed simulants said they had at some point in time diverted their stimulant medication. CONCLUSION: The diversion of stimulants by 10th graders in Iceland is quite common compared to studies from other countries where the prevalence is closer to 5-10%. These findings demonstrate the importance of carefully overseeing stimulant use of adolescents, for the benefit of both those who divert as well as those diverted to.

Transplanting embryonic stem cells onto damaged human corneal endothelium.

AIM: To investigate whether human embryonic stem cells (hESCs) could be made to attach, grow and differentiate on a human Descemet's membrane (DM). METHODS: Spontaneously differentiated hESCs were transferred onto a human corneal button with the endothelial layer removed using ocular sticks. The cells were cultured on a DM for up to 15 d. The genetically engineered hESC line expressed green fluorescent protein, which facilitated identification during the culture experiments, tissue preparation, and analysis. To detect any differentiation into human corneal endothelial-like cells, we analysed the transplanted cells by immunohistochemistry using specific antibodies. RESULTS: We found transplanted cells form a single layer of cells with a hexagonal shape in the periphery of the DM. The majority of the cells were negative for octamer-binding transcription factor 4 but positive for paired box 6 protein, sodium potassium adenosine triphosphatase (NaKATPase), and Zona Occludens protein 1. In four of the 18 trials, the transplanted cells were found to express CK3, which indicates that the stem cells differentiated into corneal epithelial cells in these cases. CONCLUSION: It is possible to get cells originating from hESCs to become established on a human DM, where they grow and differentiate into corneal endothelial-like cells in vitro.

Risk factors for five-year incident age-related macular degeneration: the Reykjavik Eye Study.

PURPOSE: To establish risk factors for five-year incidence of age-related macular degeneration (AMD). DESIGN: Population-based, prospective cohort study, and risk analysis. METHODS: A random sample from the Reykjavik Population Census for individuals 50 years and older was selected. We took fundus stereo color photographs and used standard grading system to study the five-year incidence of drusen, pigmentary abnormalities, and AMD and to examine possible risk factors. A questionnaire including information on disease, medication, diet, and lifestyle from the Reykjavik Eye Study database provided additional information. RESULTS: Current alcohol consumption decreased the risk for drusen. Being married rather than divorced or widowed decreased the risk for soft drusen; being single decreased the risk of hypopigmentation as compared with being divorced or married. Both consuming dietary fiber-rich vegetables and meat and meat products once a week or less frequently was a risk factor for developing soft drusen and decreased the risk of pigmentary abnormalities. Those who had smoked 20 pack-years or more as compared with nonsmokers had decreased survival rate over the five years (odds ratio (OR) 0.46, 95% confidence interval (CI) 0.27 to 0.80; P = .006). CONCLUSIONS: Risk factors for drusen appear to differ from risk factors for pigmentary abnormalities. The effect of smoking on developing AMD is partly masked by selective mortality.

[The prevalence of sexual abuse and sexual assault against icelandic adolescents].

INTRODUCTION: Sexual abuse and sexual assaults against children and adolescents is one of the most significant threats to their health. The aim of the current study was to investigate its prevalence and effects on Icelandic teenagers in the 10th grade. MATERIAL AND METHODS: The study is based on data collected for the Icelandic part of the HBSC-project (Health and behaviour of school- aged children). Standardized questionnaires were sent to all students in 10th grade in Iceland of which 3,618 participated. The students experience of sexual abuse or assaults was assessed by asking them how often they had been against their will a) touched in a sexual way, b) made to touch someone else in a sexual way, c) the subject of an attempted rape or d) subjected to rape. RESULTS: The results showed that 14.6% (527) participants had experienced sexual abuse or assault. Of these, 4.5% (162) had one such experience but 10.1% had either suffered certain type of abuse or assault more than once, or had experienced more than one kind. About 1% of participants (35) said that they had suffered many times from many forms of abuse and assaults. The prevalence of poor mental well-being and risk behaviour was much higher amongst those that had experienced sexual abuse or assault. CONCLUSION: Although the results show that the prevalence of sexual abuse and assault against Icelandic adolescents is similar to other Western countries, we find it to be higher than a previous study a decade ago. KEY WORDS: Sexual abuse, sexual assault, adolescents. Correspondence: Arsaell Mar Arnarsson, aarnarsson@unak.is.

Five-year refractive changes in an adult population: Reykjavik Eye Study.

PURPOSE: To study refractive changes over the course of 5 years in citizens of Reykjavik 50 years and older at baseline. METHODS: The cohort was a population-based random sample of citizens 50 years and older. Eight hundred forty-six of the 958 survivors (88.2%) underwent a 5-year follow-up examination. Refraction and keratometry were performed using a Nidek (Gamagori, Japan) ARK 900 autorefractor keratometer. Typing and grading of lens opacification was carried out using Scheimpflug slit-lamp and retroilluminated images (Nidek EAS 1000), and axial length was measured by Nidek Echoscan 800. RESULTS: Seven hundred fifty-seven right eyes were available for refraction analysis. In the 50- to 59-year age group and the 60- to 69-year age group at baseline, there was a hyperopic shift of 0.41 diopters (D) and 0.34 D, respectively, during the 5 years. There was a 0.02-D myopic shift for those 70 years of age and older at baseline during the same period. Considering all right eyes, there was a hyperopic shift of +0.29 D over the 5 years, whereas eyes with nuclear lens opacification grade II or more at baseline had a mean myopic shift of -0.65 D. There was a mean change of 0.13 D in the astigmatism against the rule during the 5 years. The data on axial length are available from the follow-up study only. The mean axial length for those 50 to 59 years of age at baseline was 23.56 mm (standard deviation [SD], 1.08 mm), as compared with 23.23 mm (SD, 1.27 mm) for those 70 years of age and older at baseline (P<0.04). CONCLUSIONS: We found a hyperopic shift for those younger than 70 years of age at baseline, although eyes with nuclear opacification grade of II or more at baseline were associated with a myopic shift. There was also an age-related shift against the rule for the axis of astigmatism during the 5-year period. Our results may be useful for predicting long-term outcome of refractive surgery.

5-year incidence of age-related maculopathy in the Reykjavik Eye Study.

PURPOSE: To examine the age- and gender-specific 5-year incidence of age-related maculopathy (ARM) and age-related macular degeneration (AMD) in citizens of Reykjavik. DESIGN: Population-based, prospective cohort study. PARTICIPANTS: The cohort was a population-based random sample of citizens 50 years and older. Of 1379 eligible subjects, 1045 had a baseline examination in 1996; 846 of the 958 survivors (88.2%) had a 5-year follow-up examination in 2001. METHODS: The incidence of various characteristics of drusen and pigmentary changes that are typical of ARM were determined using the international classification and grading system for ARM and AMD. MAIN OUTCOME MEASURES: Early ARM and AMD were assessed by masked grading of stereo fundus photographs. RESULTS: Hypopigmentation developed at 5 years in 10.7% of people 50 to 59 years of age (95% confidence interval [CI], 6.9-14.4) and in 25.7% those 70 to 79 years of age (95% CI, 18.4-33.0) at baseline. Age-related macular degeneration developed in no one who was 50 to 59 years of age at baseline. Geographic atrophy (GA) developed in 4.6% (95% CI, 1.2-7.9) and exudative AMD in none of those who were 70 years and older at baseline. CONCLUSIONS: Geographic atrophy is the predominant type of AMD in Iceland, and the ratio of GA to neovascular AMD is higher than in racially similar populations.

Cosmic radiation increases the risk of nuclear cataract in airline pilots: a population-based case-control study.

BACKGROUND: Aviation involves exposure to ionizing radiation of cosmic origin. The association between lesions of the ocular lens and ionizing radiation is well-known. OBJECTIVE: To investigate whether employment as a commercial airline pilot and the resulting exposure to cosmic radiation is associated with lens opacification. METHODS: This is a population-based case-control study of 445 men. Lens opacification was classified into 4 types using the World Health Organization simplified grading system. These 4 types, serving as cases, included 71 persons with nuclear cataracts, 102 with cortical lens opacification, 69 with central optical zone involvement, and 32 with posterior subcapsular lens opacification. Control subjects are those with a different type of lens opacification or without lens opacification. Exposure was assessed based on employment time as pilots, annual number of hours flown on each aircraft type, time tables, flight profiles, and individual cumulative radiation doses (in millisieverts) calculated by a software program. Odds ratios were calculated using logistic regression. RESULTS: The odds ratio for nuclear cataract risk among cases and controls was 3.02 (95% confidence interval, 1.44-6.35) for pilots compared with nonpilots, adjusted for age, smoking status, and sunbathing habits. The odds ratio for nuclear cataract associated with estimation of cumulative radiation dose (in millisieverts) to the age of 40 years was 1.06 (95% confidence interval, 1.02-1.10), adjusted for age, smoking status, and sunbathing habits. CONCLUSION: The association between the cosmic radiation exposure of pilots and the risk of nuclear cataracts, adjusted for age, smoking status, and sunbathing habits, indicates that cosmic radiation may be a causative factor in nuclear cataracts among commercial airline pilots.