Circadian And Overall Relationships Between Intraocular Pressure, Blood Pressure, Heart Rate And Nitric Oxide In Men

Abstract

Abstract: : Purpose:To look for relationships between circadian patterns and overall 24h means between intraocular pressure (IOP), systolic [S] & diastolic [D] blood pressure [BP], pulse pressure [PP], mean arterial pressure [MAP], & heart rate [HR] in men studied over a 34y span. Also to compare circadian patterns in these variables with circulating nitric oxide (NO) measured in year 34. Methods:22 males participated in one to six 24h studies in May 1969 (n=13), 1979 (n=14), 1988 (n=11), 1993 (n=11), 1998 (n=11) & 2003 (n=10) (age range = 22–81y) for an ongoing study of biological rhythms. Each man was clinically healthy with no history of eye disease. Sampling every 3h began at 19:00h. Bedrest was between 22:30 & 06:30h. Each 24h profile for IOP & BP (n=63), HR (n=61) and NO (n=10) was analyzed for circadian rhythm by the least–squares fit of a 24h cosine. Grouped data were analyzed for rhythm after normalizing individual series to percent of mean. 24h means were compared by simple linear regression. Results:Rhythm detection was highly significant (p<0.001) for each variable. Acrophases (peak of 24h cosine) were as follows: IOP R & L eye = 11:54h & 12:14h; MAP = 15:29h; PP = 16:18h; HR = 16:29h; PPP = 17:09h; SBP = 19:06h; DBP = 23:12h; NO = 23:44h. Age correlated positively with 24h means for IOP (r=0.32, p=0.11), HR (r=0.32, p=0.012) and DBP (r=0.30, p=0.018), while IOP correlated positively with PP (r=0.52, p<0.001), SBP (r=0.49, p<0.001), DBP (r=0.45, p<0.001), MAP, r=0.34, p=0.007) and HR (r=0.28, p=0.031), but not DBP (r=0.20, p=0.115). IOP tended to be slightly greater in the right eye vs left. Conclusions:A predictable circadian variation was found in each variable, with IOP peaking near midday, HR and BP in the afternoon or evening, and NO peaking near midnight. 24h means for IOP and each cardiovascular variable (except DBP) also showed a positive overall correlation. Relationships between IOP and other variables determined at only a single timepoint may be misleading due to differences in the timing of their highs and lows throughout the day. 24h or optimally–timed IOP measurements might increase the accuracy of patient management, as well as guide in selection of time(s) to optimize responses to pharmacological treatments.

Keywords: circadian rhythms • intraocular pressure • nitric oxide