Hematocrit value at early middle age predicts hypertension at late middle age: the Tampere adult population cardiovascular risk study, a 30-year follow-up

A 50-year-old cohort from the Tampere adult population cardiovascular risk study having hypertension and their controls were examined retrospectively at the age of 35 years, and followed up prospectively up to the age of 65 years to determine whether an early hematocrit (HCR) measurement predicts later hypertension or cardiovascular complications. A total of 307 subjects having hypertension and 579 non-hypertensive controls were chosen from the 50-year-old cohort and regrouped according to HCR values obtained when they were 35 years old, one with HCT < 45 % (n = 581), and the other, with HCT ≥ 45 % (n = 305). Hypertension and coronary artery disease (CAD) by the age of 60 years were determined by self-report and the National Hospital Discharge Registry. Outcomes for death up to the age of 65 years were collected from the National Statistics Centre. HCT ≥ 45 % at the age of 35 years associated with hypertension (p = 0.041) and CAD (P = 0.047) by the age of 60 years. When the subjects were followed up to the age of 65 years, HCT ≥ 45 % associated with premature cardiovascular death (P = 0.029), and death by any cause (P = 0.004). These results were obtained after adjusting for BMI-class recorded at 50 years of age. However, when outcome was also adjusted by gender, current smoking, vocational education, and state of one's health, association of the ≥ 45 % group with CAD and death was abolished. The association with hypertension remained (P = 0.007). In conclusion, there was a significant association of HCT ≥ 45 % at early middle age with subsequent hypertension.