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Education level strong predictor of incident hypertension in women
5 June 2009
MedWire News: Women’s education level independently predicts their risk for developing hypertension, an analysis of the Women’s Health Study has shown.
The study provides insight generally into the relationship between socioeconomic status and cardiovascular disease, say the authors, “by demonstrating a strong relationship even in women with a relatively narrow range of income and education.”
Furthermore, they say the study suggests there is no threshold effect, as has previously been suggested. “Thus, even the small difference between a master’s degree and a doctorate may have a substantial impact on the future cardiovascular risk of an individual,” write David Conen and team from Brigham and Women’s Hospital in Boston, Massachusetts, USA.
The researchers studied 27,207 female health professionals participants of the Women’s Health Study who did not have hypertension at baseline in 1993. They grouped the women into five categories of education level beyond high school, namely, those with: 2 or less years of health professional education; 2-4 years of health professional education; a bachelor’s degree; a master’s degree; and a doctoral degree.
They also grouped the women into six annual household income categories, defined as under $20,000, $20,000-29,999, $30,000-39,999, $40-49,999, $50,000-99,999, or $100,000 or higher.
At 2 years of follow-up, 11,421 (48.1%) of the 23,752 participants with self-reported blood pressure had progressed to a higher of the three blood pressure (BP) categories: below 120/75 mmHg; 120-129/75-84 mmHg; and 130-139/85-89 mmHg.
Rates of BP progression fell across increasing education categories, at 52.6%, 49.8%, 46.4%, 44.5%, and 42.0%, respectively. Correspondingly, they fell across increasing income groups from 55.8% to 54.6%, 51.4%, 49.0%, 46.9%, and 41.4%.
Compared with those with the lowest education level, women had 4%, 8%, 10%, and 16% lower relative risks for BP progression across increasing education categories, respectively, after multivariable adjustment for classic cardiovascular risk factors, including, notably, body mass index (p for trend<0.0001). And compared with those with the lowest income, women’s risk for BP progression increased by 1% and then decreased by 1%, 3%, 4%, and 11% across increasing income category (p for trend=0.0001).
Over the median follow-up of 9.8 years, 8248 (0.30%) of the total 27,207 participants developed hypertension. As with BP progression, there was an inverse association between age-adjusted incidence rate and education level, at incidences of 47.8, 39.7, 35.0, 34.9, and 27.7 per 1000 person-years across the lowest to the highest category. Relative risks for hypertension, in comparison with the lowest level of education, were 8%, 15%, 13%, and 26% lower across increasing education level categories in multivariable analysis.
Although a similar association with incident hypertension was observed across income groups, the trend was attenuated and no longer significant after multivariable adjustment, Conen and team note.
The researchers suggest that the stronger influence of education versus income may relate to misclassification bias. “Income can fluctuate over time and thus is susceptible to bias,” they write. “Furthermore, income does not necessarily reflect an individual’s wealth, which may influence… health behavior. In contrast, education is typically determined relatively early in life, is less subject to fluctuation thereafter, and therefore much less susceptible to misclassification bias.”
“These negative patterns for provoking disease cannot be treated by drugs given to individuals,” commented Peter Nilsson (Lund University, Malmo, Sweden) in an accompanying editorial. “They should instead be the targets for public health efforts to increase the availability of education for all as well as counteracting social inequities.”
