['Cerebrovascular reactivity (CVR) is a hemodynamic parameter representing the increase in normal cerebral artery blood flow in response to a vasodilatory stimulus such as hypercapnia.', 'The aim of the study was to assess CVR using transcranial Doppler ultrasound and the breath-holding test (BHT) in normotensive patients with non-insulin-dependent diabetes mellitus (NIDDM). The cerebrovascular response to hypercapnia was evaluated in relation to risk factors for cerebral microangiopathy.', 'The study was carried out in a group of 34 normotensive NIDDM patients and a group of 31 sex- and age-matched normal controls. The NIDDM group was subdivided into 21 patients with microangiopathic complications (Group A, 12 men, 9 women; mean age 58.77 +/- 8.91 years) and 13 patients with no such complications (Group B, 8 men, 5 women; mean age 56.34 +/- 9.83 years). The control group comprised 17 men and 14 women (Group C, mean age 58.43 +/- 6.31 years). Exclusion criteria were hypertension and past or present symptomatic cerebrovascular disease. The BHT consisted of spontaneous hypercapnia induced by holding the breath for 20 seconds. CVR was estimated in relation to the increase in the mean flow velocity (MFV) compared with the basal velocity in both middle cerebral arteries during hypercapnia.', 'In Group A, the CVR was significantly decreased in 71.42% of patients, whereas in Group B only 30.76% of patients presented with mildly to moderately impaired CVR. Predictors for impaired % increase in the MFV during the BHT demonstrated by univariate regression analysis were: duration of diabetes (r = 0.802; P < 0.0001), fibrinogen (r = 0.574; P < 0.0001), C-reactive protein (r = 0.525; P < 0.001), proteinuria (r = 0.924; P < 0.0001) and serum creatinine (r = 0.969; P < 0.0001). Multivariate regression analysis showed as predictors: duration of diabetes (P < 0.0001), proteinuria (P < 0.0001) and serum creatinine (P < 0.0001).'] Is cerebrovascular reactivity impaired in patients with non-insulin-dependent diabetes mellitus and microangiopathy?