Recently, some research seems to indicate that being born too early (preterm birth) presents an increased risk for the development of both high blood pressure (hypertension) and cardiovascular disease (CVD) in adult life.
It is not clear how much of the CVD risk can be attributed to hypertension, however. A recent paper explored this association, showing that both these outcomes are independently linked to preterm birth.
CVD is a killer among women, accounting for more deaths yearly than cancer. The major risk factor for CVD is hypertension, which is estimated to reduce life expectancy among women by almost five years. But there is interesting evidence suggesting that hypertension is more prevalent among adults born before 37 completed weeks of pregnancy.
The current study, published in The American Journal of Cardiology, discusses the risk of hypertension and CVD in adult women concerning their birth history. Such a study has not been reported yet in America.
The study used data from the Women’s Health Initiative, a longitudinal cohort study with a prospective design. It included ~2,300 women with self-reported preterm birth between the ages of 50 and 79 years.
What did the study show?
Women who reported a preterm birth history were more often White and had a higher body mass index (BMI). They were also more likely to be poorer, to have diabetes mellitus and hypertension, and to be on more antihypertensive medications.
The results showed that the risk of developing hypertension of new onset, of coronary heart disease (CHD) and of CVD, were all higher by a quarter in those who had been born preterm. In the latter cohort, the odds for hypertension were >25% higher in the preterm cohort, at a prevalence of 37% vs. 33% in those adults who had been born at term.
Similarly, early-onset hypertension (developing before the age of 50 years) was identified in ~15% vs. ~12% of preterm and term-born individuals, respectively, showing an increase in the risk by a third. New-onset hypertension was observed to be more likely by 10% in the preterm cohort, at 53% vs. 51% in the term-born.
More women in the preterm-born cohort were on antihypertensive medication. There was no significant association between the risk of CVD and the time of birth,
Conversely, women in the preterm cohort who did not have hypertension had a higher CVD risk by 20% than normotensive term-born women. Similarly, their risk for CHD was a quarter higher than for the latter cohort. This difference was not observable among those with hypertension, with both groups showing ~70% to 80% increased risk for CVD.
What are the implications?
Preterm birth increases the risk of hypertension and coronary heart disease. With 10% of the population born preterm, birth history should be assessed as a CVD risk factor.”
Earlier research showed increased systolic blood pressure by 2-8 mm Hg in those with a history of preterm birth, beginning at six years of age. This was notable in females. Moreover, adults with a history of being born preterm had more difficulty controlling their hypertension.
Even a small elevation in blood pressure produces a significant clinical impact that can affect lifelong health. The lack of significant difference between the risks for CHD in both cohorts when hypertension was already present could be explained by the strength of association of the latter with this event, hiding the effects of preterm birth. Alternatively, the women born preterm in this cohort might have been treated with suboptimal protocols at birth since neonatal intensive care units were not yet in existence at the time.
It has also been shown that preterm-born women have a higher risk of heart disease and death due to CVD and the chances of a stroke are increased by 25% and 32%, respectively, in preterm- and term-born women with uncontrolled hypertension. Both of these are also partially attributable to the low birth weight of many women in the preterm cohort, which is itself associated with hypertension and CVD. Nonetheless, the fact of preterm birth appears to be an independent risk factor, as other term-born women with low birth weight have a lower association with these outcomes.
This is the first analysis of hypertension and hypertension-related incidents of CHD and CVD in the largest known US preterm cohort of women aged 50 to 79 years.”
While the management of preterm birth has changed in recent decades, the need to recognize this event as a risk factor for CVD must be acknowledged to allow for proper and timely intervention.