Evaluation of the associations between changes in intraocular pressure and metabolic syndrome parameters: a retrospective cohort study in Japan

OBJECTIVE: The contributions of highly correlated cardiovascular risk factors to intraocular pressure (IOP) are not clear due to underlying confounding problems. The present study aimed to determine which metabolic syndrome parameters contribute to elevating IOP and to what extent. DESIGN: Retrospective cohort study. SETTING: A private healthcare centre in Japan. PARTICIPANTS: Individuals who visited a private healthcare centre and underwent comprehensive medical check-ups between April 1999 and March 2009 were included (20 007 in the cross-sectional study and 15 747 in the longitudinal study). PRIMARY AND SECONDARY OUTCOME MEASURES: Changes in IOP were evaluated in terms of ageing and changes in metabolic syndrome parameters. Pearson's correlation coefficients and mixed-effects models were used to examine the relationship of changes in IOP with ageing and changes in metabolic syndrome parameters in cross-sectional and longitudinal studies, respectively. RESULTS: In the cross-sectional study, IOP was negatively correlated with age and positively correlated with waist circumference, high-density lipoprotein cholesterol (HDL-C) levels, triglyceride levels, systolic blood pressure (SBP), diastolic blood pressure (DBP) and fasting plasma glucose (FPG) levels. In the longitudinal multivariate analysis, the associated IOP changes were −0.12 (p<0.0001) mm Hg with male sex; −0.59 (p<0.0001) mm Hg with 10 years of ageing; +0.42 (p<0.0001) mm Hg with 1 mmol/L increase in HDL-C levels; +0.092 (p<0.0001) mm Hg with 1 mmol/L increase in triglyceride levels; +0.090 (p<0.0001) mm Hg with 10 mm Hg increase in SBP; +0.085 (p<0.0001) mm Hg with 10 mm Hg increase in DBP; and+0.091 (p<0.0001) mm Hg with 1 mmol/L increase in FPG levels. CONCLUSIONS: Elevation of IOP was related to longitudinal worsening of serum triglyceride levels, blood pressure and FPG and improvement in serum HDL-C levels.