Age related changes in intraocular pressure in a large Japanese population- A cross-sectional and longitudinal study

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 w omen 20 to 79 years of age. They were office workers and their family membe rs who had received annual health examinations from 1989 to 1997. The recor ds of the participants who received health examinations were reviewed retro spectively. Each participant was examined according to a standard protocol, including tonometry with a noncontact tonometer, anthropometric measuremen ts, and blood pressure measurements. The data from the subjects' most recen t visit were analyzed cross-sectionally. The data from the 68,998 men and w omen of the total participants who were bom between the 1920s and 1960s wer e used in longitudinal analysis. Testing: Tonometric and anthropometric measurements. Main Outcome Measures: Mean values of IOP, systolic blood pressure, diastol ic blood pressure, and BMI were determined. The relationship among IOP, age , systolic blood pressure, diastolic blood pressure, and BMI was studied us ing 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 th e mixed effect model. Results: The mean (+/- standard deviation) IOP values for men and women wer e 11.9 +/- 2.5 and 11.5 +/- 2.4 mmHg, respectively. In cross-sectional anal ysis, IOP decreased significantly with age (P < 0.001). However, longitudin al analysis showed that IOP increased significantly with age in both men an d women (P < 0.001). Systolic blood pressure and BMI were positively correl ated 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 tha t birth cohort differences in ocular characteristics influence IOP in the J apanese population.