Temporal changes in cardiorespiratory fitness and the incidence of hypertension in initially normotensive subjects

Objectives: Low-cardiorespiratory fitness (CRF) has been associated with incident hypertension, but whether temporal changes in CRF are associated with incident hypertension in initially normotensive subjects are not known. We investigated the relationship of baseline CRF and longitudinal changes in CRF with incident hypertension in initially normotensive subjects. Methods: Subjects were 3,831 men who participated in two health examinations during 1998-2009. All subjects were free of cardiovascular diseases and hypertension at baseline. CRF was directly measured by peak oxygen uptake using expired gas analysis during a standard treadmill test. Results: During an average of 5 years of follow-up, 373 (9.7%) subjects developed hypertension. The incidence of hypertension was inversely associated with baseline CRF quartiles [Q1 (lowest) 11.8%, Q2 10.4%, Q3 9.1%, and Q4 (highest) 7.5%; P < 0.05 for trend]. The relative risk (RR) of incident hypertension in the lowest CRF quartile versus the highest CRF quartile was 1.69 (95% CI: 1.22-2.34) after adjustment for risk factors. Each metabolic equivalent increment higher peak oxygen uptake at baseline examination was associated with 10% (RR 0.90, 95% CI: 0.83-0.98) lower incidence of hypertension in multivariate adjusted model. Subjects whose CRF decreased (<-1.18 ml/kg/min per year) over time had a 72% increased risk in developing hypertension (RR 1.72, 95% CI: 1.20-2.49) compared to subjects with increased CRF (>0.13 ml/kg/min per year) after adjustment for risk factors. Conclusion: These results demonstrate that both baseline CRF levels and changes in CRF over time were associated with the incidence of hypertension independent of risk factors.