Nondipping pattern and carotid atherosclerosis: a systematic review and meta-analysis

Evidence on the association of nondipping pattern with carotid atherosclerosis is scarce. We performed a meta-analysis in order to provide comprehensive information on subclinical carotid alterations in nondipping as compared with dipping individuals. A computerized search was performed using PubMed, OVID, EMBASE and Cochrane library databases from 1 January 1990 up to 31 March 2015. Full articles providing data on carotid intima-media thickness (IMT) and plaque in nondipping and dipping individuals, as assessed by ultrasonography, were analyzed. A total of 2753 adult individuals (1003 nondipping and 1750 dipping) included in 13 studies were considered. Common carotid IMT was higher in nondipping than in dipping individuals [807 ± 36  μm vs. 746 ± 28  μm, standard means difference, SMD: 0.37 ± 0.09, confidence interval (CI): 0.19-0.56, P < 0.01]. From data on plaque prevalence provided by five studies, the odds ratio for carotid plaques resulted 67% higher in nondipping (95% CI: 1.26-2.21, P < 0.01) than in dipping individuals. Our findings support an association between nondipping pattern and increased risk of subclinical carotid alterations. In a practical perspective, the present meta-analysis reinforces the view that an effective blood pressure control over the entire 24-h period, in particular at night, may prevent the progression of vascular damage associated with nondipping phenotype.