Efficacy of Chinese Eye Exercises on Reducing Accommodative Lag in School-Aged Children: A Randomized Controlled Trial

Purpose

To evaluate the efficacy of Chinese eye exercises on reducing accommodative lag in children by a randomized, double-blinded controlled trial.

Methods

A total of 190 children aged 10 to 14 years with emmetropia to moderate myopia were included. They were randomly allocated to three groups: standard Chinese eye exercises group (trained for eye exercises by doctors of traditional Chinese medicine); sham point eye exercises group (instructed to massage on non-acupoints); and eyes closed group (asked to close their eyes without massage). Primary outcome was change in accommodative lag immediately after intervention. Secondary outcomes included changes in corrected near and distant visual acuity, and visual discomfort score.

Results

Children in the standard Chinese eye exercises group had significantly greater alleviation of accommodative lag (-0.10D) than those in sham point eye exercises group (-0.03D) and eyes closed group (0.07D) (P = 0.04). The proportion of children with alleviation of accommodative lag was significantly higher in the standard Chinese eye exercises group (54.0%) than in the sham point eye exercises group (32.8%) and the eyes closed group (34.9%) (P = 0.03). No significant differences were found in secondary outcomes.

Conclusion

Chinese eye exercises as performed daily in primary and middle schools in China have statistically but probably clinically insignificant effect in reducing accommodative lag of school-aged children in the short-term. Considering the higher amounts of near work load of Chinese children, the efficacy of eye exercises may be insufficient in preventing myopia progression in the long-term.

Trial Registration

ClinicalTrials.gov NCT01756287     

Prevalence and Associated Factors of Myopia in High-School Students in Beijing

Purpose

To evaluate prevalence and associated factors for myopia in high school students in Beijing.

Methods

Grade 10 and 11 high school students were randomly selected from nine randomly selected districts of Beijing. The students underwent non-cylcoplegic auto-refractometry and an interview.

Results

Out of 4798 eligible students, 4677 (93.4%) students (mean age:16.9±0.7years;range:16–18 years) participated. Mean refractive error of right eyes and left eyes was −2.78±2.29 diopters and −2.59±2.50 diopters, respectively. Prevalence of myopia (defined as ≤ −1.00 diopters in the worse eye) was 80.7% (95% Confidence Interval (CI): 79.6–81.8%). Out of 3773 students with myopia, 1525 (40.4%) wore glasses daily. In multiple logistic regression analysis, a higher prevalence of myopia was associated with female sex (odds ratio (OR) = 1.31;95%CI:1.11–1.55), Han ethnicity (OR = 1.64;95%CI:1.28–2.11), attending key schools (OR = 1.48;95%CI:1.24,1.77), higher family income (OR = 1.37;95%CI:1.09–1.71), longer time spent for near work (OR = 1.43;95%CI:1.06–1.93), shorter near work distance (OR = 1.87;95%CI:1.55–2.26), lower frequency of active rest during studying (OR = 1.40;95%CI:1.16–1.70), and parental myopia (OR = 2.28;95%CI:1.80–2.87). The interaction between distance from near work and time spent for near work was statistically (P = 0.03) significant. In multiple logistic regression analysis, higher prevalence of high myopia (≤-6.0 diopters) was associated with studying in key schools (OR = 1.38;95%CI:1.05,1.81), lower frequency of active rest during studying (OR = 1.40;95%CI:1.09,1.79), and a higher number of myopic parents (OR = 2.66;95%CI:2.08,3.40).

Conclusions

A prevalence of about 80% for myopia and a prevalence of about 10% for high myopia in students aged 16 to 18 years and attending classes of grade 10 and 11 in a Chinese metropolitan region is another example of the high prevalence of moderate and high myopia in metropolitan areas of China. With this young myopic generation getting older, myopia as cause for visual impairment and blindness may further increase in importance. Future studies may address whether active rests during studying with looking into the distance are preventive against myopia development or progression.     

NO EVIDENCE OF ACCOMMODATION IN THE EYES OF THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS

Bottlenose dolphins ( Tursiops truncatus ) are aquatic mammals that must come to the surface to breathe. As a result, it might be expected that their eyes are adapted for both aerial and underwater vision. Earlier studies suggest that dolphins are emmetropic ( i. e. , focused at infinity) in water, and in some cases, emmetropic in air, although the mechanisms that permit these animals to see well in both media are not well understood. Nor is it known whether they can accommodate to focus sharply on objects at different distances. We employed video photoretinoscopy to investigate the possibility of an active accommodative mechanism in the eyes of the bottlenose dolphin in water. Measurements of the refractive state in water indicated near emmetropia for two individuals and slight myopia (nearsightedness) for the third individual. No clear cases of accommodation were observed underwater in any of the subjects examined. Vision underwater may be used to supplement echolocation. If so, such a role might not require an accommodative mechanism.     

Near Work Related Parameters and Myopia in Chinese Children: the Anyang Childhood Eye Study

Purpose

To examine the associations of near work related parameters with spherical equivalent refraction and axial length in Chinese children.

Methods

A total of 1770 grade 7 students with mean age of 12.7 years were examined with cycloplegic autorefraction and axial length. Questions were asked regarding time spent in near work and outdoors per day, and near work related parameters.

Results

Multivariate models revealed the following associations with greater odds of myopia: continuous reading (> 45min), odds ratio [OR], 1.4; 95% confidence interval [CI], 1.1-1.8; close television viewing distance (≤ 3m), OR, 1.7; 95% CI, 1.2-2.3; head tilt when writing, OR, 1.3; 95% CI, 1.1-1.7, and desk lighting using fluorescent vs. incandescent lamp, OR, 1.5; 95% CI, 1.2-2.0. These factors, together with close reading distance and close nib-to-fingertip distance were significantly associated with greater myopia (P<0.01). Among near work activities, only reading more books for pleasure was significantly associated with greater myopia (P=0.03). Television viewing distance (≤ 3 m), fluorescent desk light, close reading distance (≤20 cm) and close nib-to-fingertip distance (≤ 2 cm) were significantly associated with longer axial length (P<0.01). Reading distance, desk light, and reading books for pleasure had significant interaction effects with parental myopia.

Conclusions

Continuous reading, close distances of reading, television viewing and nib-to-fingertip, head tilt when writing, reading more books for pleasure and use of fluorescent desk light were significantly associated with myopia in 12-year-old Chinese children, which indicates that visual behaviors and environments may be important factors mediating the effects of near work on myopia.     

Effect of age on the efficacy of Zn-diethylenetriaminepentaacetic acid therapy for removal of Am and Pu from beagles

Decorporation of intravenously injected monomeric 241Am and 237+239Pu by the administration of 30 mumole Zn-diethylenetriaminepentaacetic acid (DTPA)/kg each day beginning 2 weeks after radionuclide injection was compared in beagles entered into the experiment when 3 months (juveniles). 1.9 years (young adults), or 10 years (mature adults) old and studied for about 5 months. DTPA therapy was most effective in the juvenile dogs and least effective in the mature adults. Retention of 241Am in the liver decreased from a pretreatment value for adults of about 50% of the injected activity to about 10% in the mature adults and less than 1% in the young adults at 140 days of treatment, while the liver retention of juveniles decreased from pretreatment values of about 16% to undetectable levels by 28 days of treatment. Plutonium retention in the liver decreased from adult pretreatment levels of about 30% of the injected activity (corrected for radioactive decay) to near 10% in the mature adults and 6% in the young adults at 140 days of treatment, while juvenile liver retention decreased from pretreatment values near 15% to undetectable levels by 56 days of treatment. Nonliver Am retention (mainly skeleton) decreased in mature adults from pretreatment values of about 45% of the injected activity to near 25%, in young adults from 35 to 20%, and in juveniles from roughly 70 to 9% by 140 days of DTPA administration. Nonliver Pu retention decreased from pretreatment values of about 50% of the injected activity (corrected for radioactive decay) for mature and young adults to about 30% by 140 days and from 75 to 16% in juveniles over the time period.     

Climatic adaptation of Drosophila buzzatii populations in southeast Australia

Variation in 19 traits possibly relevant for thermal adaptation was studied in 11 populations of Drosophila buzzatii collected in southeast Australia. Using stepwise multiple regression, the variation was compared to variation in geographic coordinates and to a set of climatic variables estimated for each collection site. For 13 of the traits, a significant part of the variation was explained by climatic variables and/or geographic coordinates, suggesting directional selection for adaptation to the environment in the majority of traits studied. In 10 of the traits, both geographic coordinates and climatic variables explained significant proportions of the variation, with R2 ranging from 0.075 to 0.58. Although larvae, pupae and adults of D. buzzatii share a common habitat, the measured traits were not correlated across life stages and gender. Also, there seemed to be special conditions in marginal populations near species borders, giving rise to nonlinear relations with latitude. Climate apparently does influence the adaptive evolution of the traits studied, but they also are affected by other factors that vary with latitude, longitude and distance to coast. These results highlight the complex challenges imposed by the environment on the adaptive process.     

Adaptive Visual Re-Weighting in Children’s Postural Control

This study investigated how children’s postural control adapts to changes in the visual environment and whether they use previous experience to adjust postural responses to following expositions. Four-, eight-, and twelve-year-old children (10 in each group) and 10 young adults stood upright inside of a moving room during eight trials each lasting one-minute. In the first trial, the room was stationary. In the following seven trials, the room oscillated at 0.2 Hz, amplitude of 0.5 cm, with the exception of the fifth trial, in which the room oscillated with amplitude of 3.2 cm. Body sway responses of young adults and older children down-weighted more to the increased visual stimulus amplitude when compared to younger children. In addition, four- and eight-year-old children quickly up-weighted body responses to visual stimulus in the subsequent two trials after the high amplitude trial. Sway variability decreased with age and was greatest during the high-amplitude trial. These results indicate that four year olds have already developed the adaptive capability to quickly down-weight visual influences. However, the increased gain values and residual variability observed for the younger children suggest that they have not fully calibrated their adaptive response to that of the young adults tested. Moreover, younger children do not carry over their previous experience from the sensorial environment to adapt to future changes.     

人眼微光下夜近视机制的研究

本文利用激光散斑屈光测试系统详细探讨了夜近视(night myopia)的产生机制。夜近视在环境亮度降低到产生暗视觉时出现,并随亮度继续降低而增大,平均值为1.35D。实验证明眼睛球差和色差不是造成夜近视的主要因素。夜近视数值在暗适应过程中呈增大的趋势。在暗视觉时,由于视野中缺少适宜的刺激,眼睛处于暗焦(dark focus)休止状态,这是造成夜近视的主要原因。     

Size Estimates in Ebbinghaus Illusion in Adults and Children of Different Age

Psychophysical experiments were performed with the participation of 297 subjects (adults and 6- to 17-year-old children and adolescents). Perception of the size of a central stimulus surrounded by other stimuli was studied. Subjects had to estimate the size of a circle with a diameter of 22 angular min, which was surrounded by four similar figures with a diameter of either 11 or 44 angular min at a distance of either 11 or 33 angular min. The misperception of the stimulus size was dependent on the subject's age, the distance between the circles, and the size of the flanking circles. The smaller flanking circles located at any distance produced size underestimation in younger children; these circles led to size overestimation in case of their location at a short distance in most adults and adolescents. The larger flanking circles produced underestimation in all age groups, but, in adults, unlike children, this illusion decreased with increasing distance. The illusion mechanism and its possible connection with selective attention are discussed.     

Cytokine fibroblast growth factor 10 (FGF10) polymorphisms are associated with risk of myopia in young children

Myopia has become a major public health issue worldwide. Identification of genetic loci related to myopia in young children may advance our knowledge of the pathogenesis of myopia. Fibroblast growth factor 10 (FGF10) plays essential roles for the development of myopia through modulating extracellular matrix-associated genes. Studies revealed that genetic variants of FGF10 were associated with extreme myopia in adults. However, their associations with susceptibility of myopia in young children, which are less affected by confounding factors and more suitable for studying genetic factors of myopia, have not been explored. In the current study, we evaluated 13 tagSNPs that captured 100% of genetic variation in the FGF10 gene region for their associations with myopia in a large Chinese case-control study with 900 myopia children and 900 nonmyopia children. We found rs2973644 was significantly associated with increased risk of myopia (odds ratio [OR]: 1.26; 95% confidence intervals [CI]: 1.06-1.49; P = 0.009). furthermore, rs339501 (OR: 1.73; 95% CI: 1.18-2.53; P = 0.005), rs2973644 (OR: 1.57; 95% CI: 1.13-2.19; P = 0.007), and rs79002828 (OR: 1.83; 95% CI: 1.20-2.77; P = 0.005) were significantly associated with increased risk of high myopia in young children. Functional assessment of rs2973644 by luciferase assays revealed the risk G allele causes a higher expression level of FGF10 than the protective A allele. Our results do support that genetic variants of cytokine FGF10 are associated with susceptibility of myopia (as well as high myopia) in young children and further exploration are needed for myopia in children.     

Molt-related and size-dependent differences in the escape response and post-threat behavior of the American lobster, Homarus americanus

Videotaped recordings of adult lobsters of different molt stages were analyzed. The escape response of adults was compared with that of juveniles recorded in an earlier study. Juvenile lobsters always respond to a threat with escape behavior irrespective of their molt stage, but in adults the probability of eliciting a response was a function of molt stage: more hard-shelled (intermolt stage C) and (premolt stage D) animals tailflipped than did soft-shelled (postmolt stages A and B) animals. The number, frequency, and duration of tailflips, and the average distance swum by animals in each molt stage were measured for the entire escape response, for the initial power swim, and for the subsequent swims. These measurements were used to compute several parameters: velocity, acceleration, force, and work; average distance traveled in a tailflip for each kilogram of body weight (distance/kg/tailflip); and average distance traveled for each bodylength (distance/bodylength). Among adults, intermolt (stage C) lobsters traveled significantly farther and faster than postmolt animals (stages A and B). Among juveniles, late postmolt (stage B) animals traveled farther. Among adults, although the total number of tailflips and the duration of the response were not significantly different among molt stages, the number of tailflips/second (frequency) and distance traveled/kg/tailflip were greater for intermolt animals. In juvenile intermolts, however, frequency and distance/kg/tailflip were markedly lower than in the premolt stages. Although values were lower than intermolts and premolts, postmolt adults sustained their swimming frequency, distance/kg/tailflip, and distance/bodylength for the entire escape distance (as did postmolt juveniles). These parameters then dropped off sharply for both adult and juvenile intermolt and premolt animals in the second half of the escape distance. Post-threat behaviors reveal that stage D animals have the highest aggression index and often attack the presented stimulus, whereas stage A animals are the least likely to approach the stimulus and typically back away in a non-aggressive posture. Thus, although effects of the molt cycle on adult and juvenile escape behavior are similar in some ways, other physical characteristics of adults, such as weight, allometry, and physiology, seem to become important in determining the likelihood of escape behavior and the characteristics of the escape swim in each molt stage.     

利用Poincare 散点图法检测t 波交替的指标研究

目的:利用Poincare散点图进行t波交替检测,不仅从形态上找到检测标准,进一步研究散点中有效的定量指标。方法:以European ST-T Database标准心电数据库和MIT-BIH心律失常数据库的心电信号作为检测对象,以128个连续心拍的t波中的7个点为检测数据,相邻心拍t波差分后组成新序列,并由差分序列作出散点图,观察散点形态。根据形态区别和t波交替的幅值变化特点,利用个散点到x+y=0直线的距离均值作为定量检测指标D0,为避免不同心电信号幅值影响,D0除以RQ峰值差为最终指标D,找出合适阈值判定是否存在t波交替,并与谱分析法的检测结果比较分析。结果:①从Poincare散点图形态上,存在t波交替的散点图与正常t波存在明显区别,存在t波交替则散点集中在以x+y=0为轴线的附近,形成类似椭圆的狭长形状;而正常t波形成的散点会以原点为中心均匀分布,散点形态为圆形。②由t波交替的特点和散点图形态可知,定量检测指标D越小,就越有可能存在t波交替。经过大量仿真测试和谱分析法的比较,规定检测标准为,当D<=35uv时,存在t波交替;指标D与谱分析法的结论相吻合,并且两种方法的判定结果由kappa一致性检验,一致性程度好,进一步说明D指标具有优越的敏感性,是t波交替检测的有效指标。结论:Poincare散点图的散点分布形态和散点到x+y=0轴线的距离均值分别是是t波交替有效的定性和定量检测指标。     

New Stereoacuity Test Using a 3-Dimensional Display System in Children

The previously developed 3-dimensional (3D) display stereoacuity tests were validated only at distance. We developed a new stereoacuity test using a 3D display that works both at near and distance and evaluated its validity in children with and without strabismus. Sixty children (age range, 6 to 18 years) with variable ranges of stereoacuity were included. Side-by-side randot images of 4 different simple objects (star, circle, rectangle, and triangle) with a wide range of crossed horizontal disparities (3000 to 20 arcsec) were randomly displayed on a 3D monitor with MATLAB (Matworks, Inc., Natick, MA, USA) and were presented to subjects wearing shutter glasses at 0.5 m and 3 m. The 3D image was located in front of (conventional) or behind (proposed) the background image on the 3D monitor. The results with the new 3D stereotest (conventional and proposed) were compared with those of the near and distance Randot stereotests. At near, the Bland-Altman plots of the conventional and proposed 3D stereotest did not show significant difference, both of which were poorer than the Randot test. At distance, the results of the proposed 3D stereotest were similar to the Randot test, but the conventional 3D stereotest results were better than those of the other two tests. The results of the proposed 3D stereotest and Randot stereotest were identical in 83.3% at near and 88.3% at distance. More than 95% of subjects showed concordance within 2 grades between the 2 tests at both near and distance. In conclusion, the newly proposed 3D stereotest shows good concordance with the Randot stereotests in children with and without strabismus.     

Prevalence and Risk Factors for Refractive Errors: Korean National Health and Nutrition Examination Survey 2008-2011

Purpose

To examine the prevalence and risk factors of refractive errors in a representative Korean population aged 20 years old or older.

Methods

A total of 23,392 people aged 20+ years were selected for the Korean National Health and Nutrition Survey 2008–2011, using stratified, multistage, clustered sampling. Refractive error was measured by autorefraction without cycloplegia, and interviews were performed regarding associated risk factors including gender, age, height, education level, parent''s education level, economic status, light exposure time, and current smoking history.

Results

Of 23,392 participants, refractive errors were examined in 22,562 persons, including 21,356 subjects with phakic eyes. The overall prevalences of myopia (< -0.5 D), high myopia (< -6.0 D), and hyperopia (> 0.5 D) were 48.1% (95% confidence interval [CI], 47.4–48.8), 4.0% (CI, 3.7–4.3), and 24.2% (CI, 23.6–24.8), respectively. The prevalence of myopia sharply decreased from 78.9% (CI, 77.4–80.4) in 20–29 year olds to 16.1% (CI, 14.9–17.3) in 60–69 year olds. In multivariable logistic regression analyses restricted to subjects aged 40+ years, myopia was associated with younger age (odds ratio [OR], 0.94; 95% Confidence Interval [CI], 0.93-0.94, p < 0.001), education level of university or higher (OR, 2.31; CI, 1.97–2.71, p < 0.001), and shorter sunlight exposure time (OR, 0.84; CI, 0.76–0.93, p = 0.002).

Conclusions

This study provides the first representative population-based data on refractive error for Korean adults. The prevalence of myopia in Korean adults in 40+ years (34.7%) was comparable to that in other Asian countries. These results show that the younger generations in Korea are much more myopic than previous generations, and that important factors associated with this increase are increased education levels and reduced sunlight exposures.     

Night myopia studied with an adaptive optics visual analyzer

Purpose

Eyes with distant objects in focus in daylight are thought to become myopic in dim light. This phenomenon, often called “night myopia” has been studied extensively for several decades. However, despite its general acceptance, its magnitude and causes are still controversial. A series of experiments were performed to understand night myopia in greater detail.

Methods

We used an adaptive optics instrument operating in invisible infrared light to elucidate the actual magnitude of night myopia and its main causes. The experimental setup allowed the manipulation of the eye''s aberrations (and particularly spherical aberration) as well as the use of monochromatic and polychromatic stimuli. Eight subjects with normal vision monocularly determined their best focus position subjectively for a Maltese cross stimulus at different levels of luminance, from the baseline condition of 20 cd/m² to the lowest luminance of 22×10⁻⁶ cd/m². While subjects performed the focusing tasks, their eye''s defocus and aberrations were continuously measured with the 1050-nm Hartmann-Shack sensor incorporated in the adaptive optics instrument. The experiment was repeated for a variety of controlled conditions incorporating specific aberrations of the eye and chromatic content of the stimuli.

Results

We found large inter-subject variability and an average of −0.8 D myopic shift for low light conditions. The main cause responsible for night myopia was the accommodation shift occurring at low light levels. Other factors, traditionally suggested to explain night myopia, such as chromatic and spherical aberrations, have a much smaller effect in this mechanism.

Conclusions

An adaptive optics visual analyzer was applied to study the phenomenon of night myopia. We found that the defocus shift occurring in dim light is mainly due to accommodation errors.     

Effect of induced high myopia on functional MRI signal changes

PurposeThe current study evaluated the effect of lens-induced high myopia (IHM) on the activity of the occipital visual cortex during two visual stimuli presentations to the subjects. This was done by measuring the Blood Oxygenation Level Dependent (BOLD) signal using functional MRI (fMRI).MethodsBOLD contrast fMRI was performed with a 1.5T MRI scanner on 12 emmetropic subjects (refractive error <±0.25Diopter) with no history of neurologic disorder. IHM conditions were applied to subjects by three convex lenses of +5D, +7D and +10D. Visual stimuli with 0.34 cpd and 1.84 cpd spatial frequencies (SF) were presented as a block paradigm to the participants in three IHM states and normal vision state during fMRI data acquisition. Resultant fMRI data were compared among different refractive states.ResultsData analysis showed that IHM did not cause a significant change in the visual cortex activity throughout the presentation of 0.34 cpd SF visual stimulus and BOLD signal intensity remained approximately constant (p = 0.17). Although, fMRI responses to visual stimuli with spatial frequency of 1.84 cpd demonstrated that visual cortex activity was significantly reduced in IHM states compared to normal vision (p = 0.01), the results showed no significant differences between three different values of IHM.ConclusionsThis study shows severe blurring caused by lens induced high myopia can decrease BOLD signal intensity depending on the visual stimulus pattern details. However in the low and moderate range of spatial frequencies, blur increment from +5D up to +10D is not associated with further reduction in the BOLD signal of the occipital visual cortex.     

Deletion of SA β‐Gal+ cells using senolytics improves muscle regeneration in old mice

Systemic deletion of senescent cells leads to robust improvements in cognitive, cardiovascular, and whole‐body metabolism, but their role in tissue reparative processes is incompletely understood. We hypothesized that senolytic drugs would enhance regeneration in aged skeletal muscle. Young (3 months) and old (20 months) male C57Bl/6J mice were administered the senolytics dasatinib (5 mg/kg) and quercetin (50 mg/kg) or vehicle bi‐weekly for 4 months. Tibialis anterior (TA) was then injected with 1.2% BaCl₂ or PBS 7‐ or 28 days prior to euthanization. Senescence‐associated β‐Galactosidase positive (SA β‐Gal+) cell abundance was low in muscle from both young and old mice and increased similarly 7 days following injury in both age groups, with no effect of D+Q. Most SA β‐Gal+ cells were also CD11b+ in young and old mice 7‐ and 14 days following injury, suggesting they are infiltrating immune cells. By 14 days, SA β‐Gal+/CD11b+ cells from old mice expressed senescence genes, whereas those from young mice expressed higher levels of genes characteristic of anti‐inflammatory macrophages. SA β‐Gal+ cells remained elevated in old compared to young mice 28 days following injury, which were reduced by D+Q only in the old mice. In D+Q‐treated old mice, muscle regenerated following injury to a greater extent compared to vehicle‐treated old mice, having larger fiber cross‐sectional area after 28 days. Conversely, D+Q blunted regeneration in young mice. In vitro experiments suggested D+Q directly improve myogenic progenitor cell proliferation. Enhanced physical function and improved muscle regeneration demonstrate that senolytics have beneficial effects only in old mice.     

Homing behaviour of the giant African snail,Achatina fulica (Ferussac) (Gastropoda; Pulmonata)

Homing ability ofAchatina fulica was studied in the field by mark-recapture experiments. Snails hid in resting sites in the day and crept out in the rain or at night. Young adults dispersed for longer distance than old adults. Old adults seldom changed resting sites, while young adults changed them left almost every day. It was only young adults that the study site or came in from other areas. In transfer experiments, old adults returned to the initial resting sites in 5 days. These results suggest that old adults have a homing ability, while young adults do not show it clearly. The homing ability ofA. fulica is age-dependent. These differences may be related to the maturation pattern of the reproductive organ.     

Evidence for reduced sympatholysis in leg resistance vasculature of healthy older women

Inhibition of a sympathetic stimulus (i.e., sympatholysis) during forearm exercise is reduced with age in women. This age-related alteration has not been characterized in the lower extremity vasculature of women, and the potential for blunting of the conduit artery dilatory response to a sudden increase in shear stress [flow-mediated dilation (FMD)] has not been examined in older adults of either sex. In the present study, we assessed popliteal artery diameter and velocity (Doppler ultrasound) in 16 young (23 +/- 1 yr) and 14 older (69 +/- 1 yr) women after 5 min of distal calf occlusion (FMD), 3 min of hand immersion in ice water [cold pressor test (CPT)], and 5 min of distal calf occlusion combined with hand immersion in ice water (FMD+CPT). Peak popliteal conductance after 5-min ischemia was not significantly different in young vs. older women. During the combined stimulus (FMD+CPT), the magnitude of vasoconstriction in the calf (reduction in peak popliteal artery conductance) was similar (5-8%), despite reduced resting adrenergic sensitivity to CPT [young (Y): -27.3 +/- 3.8%; older (O): -15.8 +/- 2.2%; P < 0.05] and blunted muscle sympathetic nerve activity responses to CPT (Y: 12.7 +/- 3.6 bursts/min; O: 7.8 +/- 2.5 bursts/min; P < 0.05) in older women. Popliteal FMD, normalized to the shear stimulus, was attenuated by 60-70% in older women. Peak popliteal diameter, measured during the combined stimulus (FMD+CPT), was blunted in young but not in older women (Y FMD: 5.5 +/- 0.1 mm; Y FMD+CPT: 5.4 +/- 0.1 mm; P = 0.03; O FMD: 5.8 +/- 0.2 mm; O FMD+CPT: 5.8 +/- 0.2 mm). These results confirm previous findings of diminished reactivity in the conduit arteries of older humans and provide the first evidence of reduced sympatholysis in the leg resistance vasculature of older women.     

Age Differences in the Neuroelectric Adaptation to Meaningful Sounds

Much of what we know regarding the effect of stimulus repetition on neuroelectric adaptation comes from studies using artificially produced pure tones or harmonic complex sounds. Little is known about the neural processes associated with the representation of everyday sounds and how these may be affected by aging. In this study, we used real life, meaningful sounds presented at various azimuth positions and found that auditory evoked responses peaking at about 100 and 180 ms after sound onset decreased in amplitude with stimulus repetition. This neural adaptation was greater in young than in older adults and was more pronounced when the same sound was repeated at the same location. Moreover, the P2 waves showed differential patterns of domain-specific adaptation when location and identity was repeated among young adults. Background noise decreased ERP amplitudes and modulated the magnitude of repetition effects on both the N1 and P2 amplitude, and the effects were comparable in young and older adults. These findings reveal an age-related difference in the neural processes associated with adaptation to meaningful sounds, which may relate to older adults’ difficulty in ignoring task-irrelevant stimuli.