Intraocular pressure in samples of elderly Finnish and Swedish men and women

Plasma phospholipid PUFAs are associated with greater muscle and knee extension strength but not with changes in muscle parameters in older adults

BACKGROUND

Muscle mass, intermuscular adipose tissue, and strength are important indicators of physical function. Dietary fatty acids (FAs) have been associated with muscle parameters such as larger size and higher strength, but large, population-based longitudinal data in older adults who are at risk of functional decline are lacking.

OBJECTIVE

The objective of this study was to investigate associations between plasma phospholipid polyunsaturated fatty acids (PUFAs) and measures of muscle size, intermuscular adipose tissue, and muscle strength cross-sectionally and after 5 y of follow-up.

METHODS

Data are from the Age, Gene/Environment Susceptibility-Reykjavik Study, a prospective cohort aged 66-96 y at baseline. The analytic sample included 836 participants with cross-sectional measures of muscle parameters and 459 participants with data on change in muscle parameters. PUFAs were assessed at study baseline through use of GC. Muscle parameters were assessed at baseline and after a median of 5.2 y. Muscle area and intermuscular adipose tissue were assessed with computed tomography. Maximal grip strength and knee extension strength were assessed with dynometers. Relative changes in muscle parameters (%) were calculated. Multivariate linear regression was performed to calculate unstandardized regression coefficients and P values for trends across tertiles of FAs are reported.

RESULTS

Higher concentrations of total PUFAs were cross-sectionally associated with larger muscle size (P-trend: 0.002) and with greater knee extension strength (P-trend: 0.038). Higher concentrations of arachidonic acid were associated with smaller muscle size (P-trend: 0.015). Greater linoleic acid was associated with less intermuscular adipose tissue (P-trend: 0.004), whereas eicosapentaenoic acid (20:5n-3) was positively associated (P-trend: 0.047). Longitudinal analyses showed positive associations for α-linolenic acid with increased knee extension strength (P-trend: 0.014). No other associations were observed.

CONCLUSIONS

These data illustrate the complex relation between plasma phospholipid PUFAs and muscle parameters; inconsistent cross-sectional relations with muscle size, intermuscular adipose tissue, and strength, and little evidence of a role in changes in muscle parameters.

Age-related changes in the human visual system and prevalence of refractive conditions in patients attending an eye clinic

PURPOSE

To retrospectively report the trends of change in several parameters of the human visual system over a wide age range in patients attending an eye clinic.

SETTING

University of Valencia, Valencia, Spain.

METHODS

The clinical records of 2654 patients were retrospectively reviewed, and the age, sex, spherocylindrical refraction, visual acuity, keratometry, and intraocular pressure were obtained. Descriptive values for each parameter and the correlations with age and between different parameters were calculated. Vectorial components of refraction, including blur, were also derived from clinical refractive data and then analyzed.

RESULTS

Several parameters changed significantly with age, particularly in patients in their sixties and older. An increase in the blur component was mainly associated with astigmatic progression and a trend toward against-the-rule orientation and had the highest correlation with total astigmatism (r= -0.319; P<.001) and visual acuity (r= -0.442; P<.001). Refractive conditions had the most homogeneous distribution in the first decade of life and the most heterogeneous distribution in the group between 61 years and 70 years.

CONCLUSIONS

Best corrected visual acuity began to decrease after the 50s, while changes in the blur component were not patent until the 60s to 70s. This could be explained by the poorer optical quality of the human eye in adulthood and elderly persons. Clinically, these changes could be attributed to changes in ocular astigmatism and have an impact on the best visual acuity achievable with optical compensation.

Heritability of intraocular pressure in older female twins

PURPOSE

To examine the heritability of intraocular pressure (IOP) among older women not diagnosed as having glaucoma.

DESIGN

Cross-sectional twin study.

PARTICIPANTS

94 monozygotic (MZ) and 96 dizygotic (DZ) female twin pairs aged 63-76 years and not diagnosed as having glaucoma.

METHODS

Intraocular pressure was measured using a noncontact tonometer. The contributions of genetic and environmental factors to individual differences in IOP were estimated by applying an independent pathway model to twin data.

MAIN OUTCOME MEASURES

Contribution of genetic and environmental effects to the variation in IOP among MZ and DZ twins.

RESULTS

Mean IOP of the study population was 14.1 mmHg (+/- standard deviation 3.1) with no differences observed neither between the MZ and the DZ individuals, nor between the left and the right eyes. The pair-wise correlations for IOP of the right eye were .61 in MZ and .25 in DZ and for the left eye .63 and .42. The phenotypic correlation between the left and the right eye IOP was high (r = 0.81), suggesting that they were indices of a single trait. Quantitative genetic modeling revealed that for both eyes 64% (95% confidence interval [CI], 53-71) of the variance in IOP was explained by additive genetic effects and 18% (95% CI, 11-27) by nonshared environmental factors in common. In addition, 18% (95% CI, 15-23) of the variance in IOP was explained by nonshared environmental factors specific to each eye.

CONCLUSIONS

Additive genetic influences explained most of the individual differences in IOP among older women not diagnosed as having glaucoma. Because elevated IOP is an important risk factor for glaucoma, genetic factors underlying IOP may have a significant role in determining the risk for glaucoma, a complex progressive disease leading to death of ganglion cells.