Body mass index and visual impairment in Israeli adolescents: A nationwide study.

BACKGROUND: Previous research on the association between body mass index (BMI) and visual impairment (VI) in youth has reported inconsistent findings. We aimed to investigate this association in a national cohort of Israeli adolescents. METHODS: This retrospective, population-based, cross-sectional study included 1 697 060 adolescents (56.4% men; mean age 17 years) who underwent mandatory pre-military service assessments from 1993 to 2017. BMI was classified based on the US age- and sex-matched percentiles. Unilateral or bilateral VI was classified as best-corrected visual acuity (BCVA) worse than 6/9 in either or both eyes, respectively. Sex-stratified regression models adjusted for sociodemographic variables were used to analyse the BMI-VI relationship. RESULTS: Overall, 17 871 (1.05%) and 5148 (0.30%) adolescents had unilateral and bilateral VI, respectively. Compared with high-normal BMI (50th to 85th percentile), adjusted odds ratios (ORs) for unilateral and bilateral VI gradually increased with higher BMI, reaching 1.33 (1.13-1.55) and 1.80 (1.37-2.35) in men with severe obesity, and 1.51 (1.24-1.84) and 1.52 (1.08-2.14) in women with severe obesity, respectively. Men with underweight also had increased ORs for unilateral and bilateral VI (1.23; 1.14-1.33 and 1.59; 1.37-1.84, respectively), a pattern not observed in women (0.96; 0.86-1.07 and 1.02; 0.83-1.25, respectively). Results were maintained when the outcome was restricted to mild VI, as well as in subgroups of adolescents with unimpaired health and those without moderate-to-severe myopia. CONCLUSIONS: Abnormal BMI, and particularly obesity, is associated with increased OR for VI in late adolescence.

Myopia and BMI: a nationwide study of 1.3 million adolescents.

OBJECTIVE: This study analyzed the association between adolescent BMI and myopia severity. METHODS: This cross-sectional study comprised 1,359,153 adolescents who were medically examined before mandatory military service. Mild-to-moderate and high myopia were defined based on right-eye refractive data. BMI was categorized based on the US age- and sex-matched percentiles. Logistic regression models were applied separately for women and men to estimate odds ratios (ORs) for myopia per BMI category. RESULTS: A total of 318,712 adolescents had mild-to-moderate myopia and 23,569 had high myopia. Compared with low-normal BMI (reference group), adjusted ORs for mild-to-moderate and high myopia increased with increasing BMI status, reaching 1.39 (95% CI: 1.23-1.57) and 1.73 (95% CI: 1.19-2.51) for men with severe obesity, respectively, and 1.19 (95% CI: 1.12-1.27) and 1.38 (95% CI: 1.14-1.65) for women with mild obesity, respectively. ORs for mild-to-moderate and high myopia were also higher in men with underweight (OR = 1.20; 95% CI: 1.18-1.23 and OR = 1.39; 95% CI: 1.30-1.47) and women with underweight (OR = 1.06; 95% CI: 1.03-1.09 and OR = 1.12; 95% CI: 1.04-1.22). The overall size effect was greater for men than women (pinteraction < 0.001), in whom the group with severe obesity did not reach statistical significance. CONCLUSIONS: BMI was associated with myopia in a J-shaped pattern, with the size effect being greater for adolescent men than women. This study indicates that both low BMI and high BMI are associated with mild-to-moderate and severe myopia.

Myopia and Early-Onset Type 2 Diabetes: A Nationwide Cohort Study.

CONTEXT: A correlation between myopia and insulin resistance has been suggested. OBJECTIVE: We investigated the association between myopia in adolescence and type 2 diabetes (T2D) incidence in young adulthood. METHODS: This population-based, retrospective, cohort study comprised 1 329 705 adolescents (579 543 women, 43.6%) aged 16 to 19 years, who were medically examined before mandatory military service during 1993 to 2012, and whose data were linked to the Israel National Diabetes Registry. Myopia was defined based on right-eye refractive data. Cox proportional models were applied, separately for women and men, to estimate hazard ratios (HRs) for T2D incidence per person-years of follow-up. RESULTS: There was an interaction between myopia and sex with T2D (P < .001). For women, T2D incidence rates (per 100 000 person-years) were 16.6, 19.2, and 25.1 for those without myopia, and with mild-to-moderate and high myopia, respectively. These corresponded to HRs of 1.29 (95% CI, 1.14-1.45) and 1.63 (1.21-2.18) for women with mild-to-moderate and high myopia, respectively, compared to those without myopia, after adjustment for age at study entry, birth year, adolescent body mass index, cognitive performance, socioeconomic status, and immigration status. Results persisted in extensive sensitivity and subgroup analyses. When managed as a continuous variable, every 1-diopter lower spherical equivalent yielded a 6.5% higher adjusted HR for T2D incidence (P = .003). There was no significant association among men. CONCLUSION: For women, myopia in adolescence was associated with a significantly increased risk for incident T2D in young adulthood, in a severity-dependent manner. This finding may support the role of insulin resistance in myopia pathogenesis.

Socio-demographic disparities in amblyopia prevalence among 1.5 million adolescents.

BACKGROUND: Amblyopia, when not diagnosed at appropriate age, leads to uncorrectable visual impairment with considerable social and financial implications. The aim of this study was to assess socio-demographic disparities in amblyopia prevalence among Israeli adolescents, in order to identify susceptible groups in the population. METHODS: A nationwide, population-based, cross-sectional study of Israeli adolescents examined between 1993 and 2017. All study participants underwent visual acuity examination with socio-demographic data and previous medical history documented. Associations were analyzed using univariable and multivariable logistic regression models. RESULTS: Among 1 334 650 Israeli-born candidates aged 17.15±0.26 years, amblyopia was diagnosed in 1.07%. The overall prevalence of amblyopia has declined from 1.59% in 1993 to 0.87% in 2017. Being in the lowest socioeconomic status and below average cognitive function scores increased the odds of amblyopia in both males [odds ratio (OR) 1.64, 95% confidence interval (CI) 1.45-1.87; OR 1.27, 95% CI 1.19-1.35, respectively] and females (OR 1.61, 95% CI 1.30-1.98; OR 1.27, 95% CI 1.18-1.36, respectively). Among males, Orthodox and ultra-Orthodox educational systems were associated with increased odds of amblyopia (OR 1.16, 95% CI 1.09-1.25; OR 1.90, 95% CI 1.73-2.09). A significantly higher prevalence of amblyopia was recorded among 219 983 immigrants (1.51%, P<0.001). CONCLUSIONS: Although the overall prevalence of amblyopia has decreased during the observed years, we found substantial evidence of socio-demographic disparities in amblyopia prevalence among adolescents, suggesting disparities in the prevention of the disease and its treatment. Demonstration of inequities at a national level could aid future guidance of health policy and augment current vision screening programs.

Combat-related ocular injuries in the Israel Defense Forces during the years 2013 to 2019.

BACKGROUND: Ocular injuries account for up to 13% of battle injuries, despite the implementation of advanced protective eyewear (PE). The aim of this study was to describe the extent of ocular injuries over the last years among Israel Defense Forces soldiers and to examine the change in PE policy introduced in 2013 and the effect of a high-intensity conflict on ocular injury characteristics. METHODS: This retrospective registry-based analysis derived data from the Israel Defense Forces Trauma Registry and included soldiers who sustained combat-related ocular injuries between the years 2013 and 2019. Demographic data and injury characteristics of casualties, as well as information regarding the use of PE, were collected and analyzed. RESULTS: A total of 2,312 military casualties were available for this study; the incidence of combat-related ocular injuries was 8.9% (n = 113). Ocular injuries occurred among male soldiers (98.2%) with a mean ± SD age of 22.7 ± 4.6 years; mechanism of injury was penetrating in 59.3% of the casualties and blunt in 22.1% of the casualties, ocular injury was isolated in 51.3% of the casualties, and others sustained concomitant injuries including head (32.7%), upper extremity injury (17.7%), lower extremity (15.9%), torso (8.0%), neck (6.2%), and other (5.9%) injuries. Ocular injuries rate was similar among casualties who used PE (11.2%) and those who did not use PE (13.0%) while injured (p = 0.596). Rate of open globe injuries was 9.1% in casualties who used PE and 39.5% (p = 0.002) in casualties who did not. CONCLUSION: Eye protection may significantly reduce ocular injuries severity. Education of the combatants on the use of PE and guidance of medical teams on proper assessment, initial treatment, and rapid evacuation of casualties are needed to improve visual outcomes of the casualties further. LEVEL OF EVIDENCE: Epidemiological study, level IV.

Remote ischemic preconditioning improves tissue oxygenation in a porcine model of controlled hemorrhage without fluid resuscitation.

Remote ischemic preconditioning (RIPC) involves deliberate, brief interruptions of blood flow to increase the tolerance of distant critical organs to ischemia. This study tests the effects of limb RIPC in a porcine model of controlled hemorrhage without replacement therapy simulating an extreme field situation of delayed evacuation to definitive care. Twenty-eight pigs (47 ± 6 kg) were assigned to: (1) control, no procedure (n = 7); (2) HS = hemorrhagic shock (n = 13); and (3) RIPC + HS = remote ischemic preconditioning followed by hemorrhage (n = 8). The animals were observed for 7 h after bleeding without fluid replacement. Survival rate between animals of the RIPC + HS group and those of the HS group were similar (HS, 6 of 13[46%]-vs-RIPC + HS, 4 of 8[50%], p = 0.86 by Chi-square). Animals of the RIPC + HS group had faster recovery of mean arterial pressure and developed higher heart rates without complications. They also had less decrease in pH and bicarbonate, and the increase in lactate began later. Global oxygen delivery was higher, and tissue oxygen extraction ratio lower, in RIPC + HS animals. These improvements after RIPC in hemodynamic and metabolic status provide essential substrates for improved cellular response after hemorrhage and reduction of the likelihood of potentially catastrophic consequences of the accompanying ischemia.

The Association Between Keratoconus and Body Mass Index: A Population-Based Cross-Sectional Study Among Half a Million Adolescents.

PURPOSE: To analyze the association between keratoconus and body mass index (BMI) among adolescents. DESIGN: Cross sectional study. METHODS: This was a nationwide, population-based study of candidates for military service in Israel attending the draft board in 2006 to 2014 who underwent an ophthalmologic examination. The study population included 579,946 males and females between 16 and 19.9 years of age. Subjects were divided into 4 groups based on adjusted BMI percentiles: underweight (8.3%), normal weight (73.9%), overweight (10.7%), and obese (7.1%). The odds for having keratoconus were compared with the normal weight group. The primary outcome measure was the odds ratio (OR) for the association between BMI groups and keratoconus. RESULTS: The prevalence of keratoconus in the general population was 164 cases per 100,000, increasing over time (P < .05). There was a greater prevalence of keratoconus among obese adolescents (270/100,000) than of overweight (179/100,000), normal weight (154/100,000), and underweight (141/100,000) adolescents. Compared with the normal weight group, the OR for obese adolescents was 1.50 (95% confidence interval [CI] 1.22-1.83; P < .05), the OR for overweight adolescents was 1.42 (95% CI 1.08-1.92; P < .05), and the OR for underweight adolescents was 0.84 (95% CI 0.65-1.09; P = .18) after adjustment for gender, age, height, country of origin, and socioeconomic status. CONCLUSIONS: This study provides strong evidence regarding the independent association between BMI and keratoconus. Overweight and obese adolescents have higher odds of having keratoconus compared with normal weight adolescents. BMI should be considered a risk factor for keratoconus and further research should elucidate how obesity is involved in the progress of keratoconus.

Association of Myopia with cognitive function among one million adolescents.

BACKGROUND: Myopia is a leading cause of visual impairment worldwide, and its increasing incidence is of public health concern. Cognitive function was associated with myopia among children, but evidence for adolescents is scarce. The purpose of this study was to determine whether myopia is associated with cognitive function, and which cognitive ability, verbal or non-verbal, is involved. METHODS: We conducted a population-based cross-sectional study of 1,022,425 Israeli candidates for military service aged 16.5-18 years. Participants underwent a comprehensive battery of tests assessing verbal and non-verbal intelligence, which yields a summarized cognitive function score (CFS). In addition, subjective visual acuity examination followed by objective non-cycloplegic refraction was carried out for each participant. Association between myopia and cognitive function was evaluated by multivariable logistic regression models adjusted for gender, age, country of origin, socioeconomic status, years of education, body mass index, height and year of examination. RESULTS: Compared to the intermediate CFS of the entire cohort, participants who had the highest CFS had 1.85-fold (95% CI, 1.81 to 1.89; P < .001) higher odds of having myopia and 2.73-fold (95% CI, 2.58 to 2.88; P < .001) higher odds of high myopia, while participants with the lowest CFS had 0.59-fold (95% CI, 0.57 to 0.61, P < .001) lower odds of having myopia. The verbal components of the cognitive function assessment had stronger associations with myopia than the non-verbal components (P < .001, for all). CONCLUSIONS: Cognitive function, especially verbal intelligence, is strongly and consistently associated with myopia among adolescents.

Early Maladaptive Cardiovascular Responses are Associated with Mortality in a Porcine Model of Hemorrhagic Shock.

BACKGROUND: Hemorrhage is a leading cause of death on the battlefield. Current methods for predicting hemodynamic deterioration during hemorrhage are of limited accuracy and practicality. During a study of the effects of remote ischemic preconditioning in pigs that underwent hemorrhage, we noticed arrhythmias among all pigs that died before the end of the experiment but not among surviving pigs. The present study was designed to identify and characterize the early maladaptive hemodynamic responses (tachycardia in the presence of hypotension without a corresponding increase in cardiac index or mean arterial blood pressure) and their predictive power for early mortality in this experimental model. METHODS: Controlled hemorrhagic shock was induced in 16 pigs. Hemodynamic parameters were monitored continuously for 7 h following bleeding. Changes in cardiovascular and laboratory parameters were analyzed and compared between those that had arrhythmia and those that did not. RESULTS: All animals had similar changes in parameters until the end of the bleeding phase. Six animals developed arrhythmias and died early, while 10 had no arrhythmias and survived longer than 6 h or until euthanasia. Unlike survivors, those that died did not compensate for cardiac output (CO), diastolic blood pressure (DBP), and stroke volume (SV). Oxygen delivery (DO2) and mixed venous saturation (SvO2) remained low in animals that had arrhythmia, while achieving certain measures of recuperation in animals that did not. Serum lactate increased earlier and continued to rise in all animals that developed arrhythmias. No significant differences in hemoglobin concentrations were observed between groups. CONCLUSIONS: Despite similar initial changes in variables, we found that low CO, DBP, SV, DO2, SvO2, and high lactate are predictive of death in this animal model. The results of this experimental study suggest that maladaptive responses across a range of cardiovascular parameters that begin early after hemorrhage may be predictive of impending death, particularly in situations where early resuscitative treatment may be delayed.

Association Between Type of Educational System and Prevalence and Severity of Myopia Among Male Adolescents in Israel.

IMPORTANCE: A substantial portion of the public is diagnosed with myopia, which increases the risk of potential sight-threatening complications. The association between study style and the development of myopia is unclear. OBJECTIVE: To analyze the association between studying in different educational systems and the prevalence and severity of myopia among Jewish male adolescents in Israel. DESIGN, SETTING, AND PARTICIPANTS: A nationwide, population-based study was conducted of 22 823 male candidates for military service in Israel aged 17 to 18 years attending the military draft board in 2013 who underwent a medical examination and a visual acuity assessment. Statistical analysis was performed from January 1 to March 31, 2018. EXPOSURES: The participants studied in 1 of 3 Israeli educational systems: secular, Orthodox, or ultra-Orthodox. The ultra-Orthodox system and, to a lesser extent, the Orthodox system involve intensive reading starting in early childhood compared with the secular system. MAIN OUTCOMES AND MEASURES: The odds ratio (OR) for the association between educational system and the prevalence and severity of myopia. RESULTS: Among the 22 823 participants (mean [SD] age, 17.7 [0.6] years), there was a higher proportion of adolescents in the ultra-Orthodox educational system with myopia (1871 of 2276 [82.2%]) compared with adolescents in the Orthodox educational system (1604 of 3189 [50.3%]) and those in the secular educational system (5155 of 17 358 [29.7%]). Compared with adolescents in the secular educational system, those in the Orthodox educational system were more likely to have myopia (OR, 2.3; 95% CI, 2.1-2.5; P < .001), as were those in the ultra-Orthodox educational system (OR, 9.3; 95% CI, 8.2-10.7; P < .001), after adjustment for age, country of origin, socioeconomic status, years of education, and body mass index. The multivariable adjusted OR for high myopia (refractive error of at least -6.0 diopters) was 4.6 (95% CI, 3.8-5.5; P < .001) for adolescents in the Orthodox educational system and 38.5 (95% CI, 30.7-48.2; P < .001) for adolescents in the ultra-Orthodox educational system compared with adolescents in the secular educational system. CONCLUSIONS AND RELEVANCE: This study provides evidence of the independent association between educational systems and the prevalence and severity of myopia. Male adolescents in the ultra-Orthodox educational system have higher odds of having myopia and high myopia. These findings suggest that study styles that involve intensive reading and other near-work activities (those done at a short working distance) play a role in the development of myopia and warrant consideration of prevention strategies.