A new study have shown that high nighttime blood pressure (BP) and/or non-dipping (lack of fall in blood pressure during nighttime) is a strong predictor for the risk of cardiovascular disease and mortality in patients with hypertension. Three factors seem to affect the night time blood pressure: chronic kidney disease, obstructive sleep apnea (OSA) or the way ambulatory blood pressure is monitored.

The aim of this study is to analyse the importance of these three factors on nighttime bloodpressure.

Hypothesis:

Central 24 hour blood pressure monitoring provides another measure of daily fluctuations in blood pressure than peripheral 24 hour blood pressure monitoring, because measurement is painless and does not interfere with activities during the daytime or night-time sleep

In chronic kidney disease and OSA the decrease in nocturnal BP is lower than in healthy subjects.

In chronic kidney disease the decrease in the nocturnal BP is inversely correlated to the severity of OSA, the severity of kidney disease, and blood pressure during daytime.

150 patients with chronic kidney disease (CKD III-IV) and 75 healthy subject is examined with both central and peripheral 24 hours blood pressure monitoring, 1 night home polygraphy to determine whether the subject has obstructive sleep apnea, and if so the degree (AHI), blood- and urine samples to determine levels of u-AQP2 og u-ENaCɣ, PRC, p-AngII, p-Aldosterone, p-Avp og p-Endothelin.

Patients, group 1:

Inclusion Criteria:

• eGFR 15-59 mL/min/1.73 m2 (estimated GFR)
• 18-80 years
• males and females

Exclusion Criteria:

• lack of desire to participate
• treatment for OSA
• malignant disease
• Abuse of drugs or alcohol
• pregnant and lactating
• incompensated heart failure
• atrial fibrillation
• liver disease (ALAT> 200)
• Severe chronic obstructive lung disease (forced expiratory volume in 1 second <50% predicted)

Healthy Subjects:

inclusion criteria

• Healthy volunteers men and women
• age 40 - 80 years
• BMI within the normal range, ie. between 18.5 to 25.0 kg/m2

exclusion Criteria

• Arterial hypertension, ie. ambulatory blood pressure> 130 mmHg systolic and / or 80 mmHg diastolic.
• a history or clinical signs of cardial, pulmonary, hepato, renal, endocrine, cerebral or neoplastic disorders
• Alcohol abuse, ie. > 14 drinks / week for women and> 21/uge for men
• Substance abuse
• Daily medicine intake/ treatment apart from oral contraceptives
• Smoking
• Pregnancy or breastfeeding
• Lack of desire to participate
• Clinically significant, discrepant results of blood or urine sample at inclusion study (ie B-hemoglobin and B-White blood cell count, p-Sodium, p-Potassium, p-creatinine, p-ALAT, p-bilirubin , p-alkaline phosphatase, p-cholesterol, p-albumin or b-glucose and urine for hematuria, albuminuria or glucosuria)
• Clinically significant differences in the electrocardiogram
• Blood Donation for the past month preceding the day on the first attempt sequence.

Group 1: Patients with chronic kidney disease, CKD stage III-IV. The patients is followed for their kidney disease at Holstebro Regional Hospital, Denmark, Medical clinic, and the are chosen to participate in the study because of this relation.

Group 2: Healthy subjects. They arerecruited through postings on public and private companies as well as advertising in local medier.