Author + information
- Panagiota Pietri, MD∗ (, )
- Charalambos Vlachopoulos, MD,
- Christina Chrysohoou, MD,
- George Lazaros, MD,
- Konstantina Masoura, MD,
- Nikolaos Ioakeimidis, MD,
- Dimitris Tousoulis, MD and
- Christodoulos Stefanadis, MD
- ↵∗1st Cardiology Department, Athens Medical School, Hippokration Hospital, Kythnou 15, 15231, Athens, Greece
Ikaria is among the 5 places in the world with the highest rates of longevity (1). Aortic stiffness, assessed by aortic pulse wave velocity (PWV), is an independent predictor of cardiovascular and all-cause mortality (2).
We evaluated aortic stiffness in 138 healthy inhabitants of Ikaria Island and investigated whether there is a differentiation between the measured and reference PWV. The population was divided into 4 age groups, each per decade: 40 to 49 years (n = 29); 50 to 59 years (n = 39); 60 to 69 years (n = 31); and ≥70 years (n = 39). Aortic stiffness was assessed by measuring carotid-femoral (aortic) PWV. Participants were non-diabetic, free from overt cardiovascular disease, and under no treatment for hypertension or dyslipidemia, corresponding to the European Reference Value Population for PWV (3). We calculated PWV using the formula PWV = 0.8(xdirect)/Δt (3). Reference values were calculated by regression equations for PWV according to blood pressure (BP) category (optimal BP: PWV = 0.000 × age + 0.83 × 10−3 × age2 + 5.55, normal BP: PWV = 0.000 × age + 0.99 × 10−3 × age2 + 5.69, high normal BP: PWV = 0.000 × age + 1.05 × 10−3 × age2 + 5.91, grade I hypertension: PWV = 0.000 × age + 1.18 × 10−3 × age2 + 6.17, grade II/III hypertension: PWV = 0.044 × age + 0.85 × 10−3 × age2 + 5.73) (3). The difference between the reference and measured PWV in each age group was studied with the paired Student t test.
The percentage of current smokers was reduced with advancing age decade (16% vs. 17% vs. 7% vs. 7%, respectively; p < 0.01). Systolic BP showed a gradual increase from younger to older inhabitants (from 131.1 ± 11.7 mm Hg to 136.7 ± 14.1 mm Hg to 142.9 ± 17.1 mm Hg to 152.1 ± 21.8 mm Hg, respectively; p < 0.01). Interestingly, no difference was observed in the values of diastolic BP across the age groups (from 81.7 ± 6.5 mm Hg to 83.9 ± 10.1 mm Hg to 80.8 ± 7.7 mm Hg to 81.7 ± 11.6 mm Hg, respectively; p = not significant). Regarding the metabolic profile, low-density lipoprotein cholesterol levels were significantly lower in the elderly group 4 compared with group 1, but no significant difference was observed between all other group comparisons (from 145.9 ± 35.1 mg/dl to 136.9 ± 35.4 mg/dl to 133.9 ± 42.5 mg/dl to 120.6 ± 35.5 mg/dl, respectively). Importantly, values of high-density lipoprotein cholesterol were similar among all groups (from 46.6 ± 10.4 mg/dl to 47.1 ± 9.7 mg/dl to 48.6 ± 8.8 mg/dl to 44.6 ± 11.3 mg/dl; p = NS), implying a constant favorable high-density lipoprotein cholesterol profile across all age groups. Plasma glucose levels did not significantly change among groups.
PWV showed a gradual increase from the fourth decade of life to the elderly (p = 0.05 for the comparison between groups 1 and 2; p < 0.01 for the comparison between all other groups). No difference between the measured and reference values was observed in subjects between 40 and 49 years old (7.98 ± 0.96 m/s vs. 7.92 ± 0.69 m/s, respectively; p = NS), but after the fifth decade of life, measured PWV was consistently and significantly lower than the reference values in all age groups (group 2: 8.71 ± 1.22 m/s vs. 9.22 ± 0.80 m/s; p < 0.01; group 3: 9.87 ± 1.17 m/s vs. 10.78 ± 0.92 m/s; p < 0.001; and group 4: 11.53 ± 2.22 m/s vs. 13.17 ± 1.54 m/s; p < 0.001) (Figure 1). In multivariate regression analysis, PWV was independently related to age group (b = 0.61; p < 0.001), mean BP (b = 0.29; p = 0.001), heart rate (b = 0.23; p = 0.006), and creatinine (b = 0.19; p = 0.01); (R2 of the model: 0.59).
In the present study, we assessed aortic stiffness in a population with high rates of longevity. Aortic stiffness increases gradually with age; however, at >50 years of age, aortic stiffening seems to be decelerated because the measured PWV was significantly lower than reference values. This finding may be attributed to either a favorable hemodynamic pattern (progressive increase in systolic BP with age, but stable diastolic BP at older ages—an excessive decrease of diastolic BP hampers coronary flow) or to beneficial genetic and metabolic backgrounds that are implicated in the process of both longevity and aortic stiffness. The favorable lipid profile and the relatively low percentage of smokers among the elderly may have contributed to the results (4). Moreover, previous results from the IKARIA study showed a favorable effect of physical activity on endothelial function, which may be related to attenuated aortic stiffening (1). Hereditary aspects of aortic elasticity may also play a role given the evidence that paternal longevity is associated with decreased PWV in offspring (5).
The cross-sectional nature of our study does not allow for conclusions regarding causality, and selection bias may have interfered. Whether this privilege of aortic mechanics can also be extended to the younger generations living in the particular island is a hypothesis that needs further investigation. Finally, aortic imaging modalities that provide structural information could have enhanced our results.
Whether aortic stiffness retains its established predictive value with increasing age is an intriguing issue, with most studies attesting to an incremental predictive ability even at older ages. Given the adverse prognostic impact of aortic stiffening on cardiovascular and total mortality, the present findings may imply a possible link between longevity and aortic stiffness.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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