Objective: To assess the influence of aging, blood pressure, and body mass index (BMI) on intraocular pressure (IOP) in a large Japanese population.
Design: Cross-sectional and longitudinal study.
Participants: The participants in this study were 69,643 Japanese men and women 20 to 79 years of age. They were office workers and their family members who had received annual health examinations from 1989 to 1997. The records of the participants who received health examinations were reviewed retrospectively. Each participant was examined according to a standard protocol, including tonometry with a noncontact tonometer, anthropometric measurements, and blood pressure measurements. The data from the subjects' most recent visit were analyzed cross-sectionally. The data from the 68,998 men and women of the total participants who were born between the 1920s and 1960s were used in longitudinal analysis.
Testing: Tonometric and anthropometric measurements.
Main outcome measures: Mean values of IOP, systolic blood pressure, diastolic blood pressure, and BMI were determined. The relationship among IOP, age, systolic blood pressure, diastolic blood pressure, and BMI was studied using the multiple linear regression model with cross-sectional analysis. In longitudinal analysis, regression coefficients of IOP against age, systolic blood pressure, diastolic blood pressure, and BMI were calculated using the mixed effect model.
Results: The mean (+/-standard deviation) IOP values for men and women were 11.9+/-2.5 and 11.5+/-2.4 mmHg, respectively. In cross-sectional analysis, IOP decreased significantly with age (P < 0.001). However, longitudinal analysis showed that IOP increased significantly with age in both men and women (P < 0.001). Systolic blood pressure and BMI were positively correlated to IOP in both the cross-sectional and longitudinal studies.
Conclusion: The authors found an inconsistency in the change in IOP against age between cross-sectional and longitudinal analysis. It is suspected that birth cohort differences in ocular characteristics influence IOP in the Japanese population.