Sex differences in hypertension and other cardiovascular diseases

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In the years following the publication of major clinical trials, we commonly see additional articles related to the original study. These provide data on subgroup analyses, specific secondary outcomes, extended follow-up, analyses that were available at the time of publication of the original article but not included in the manuscript, and data generated in the years after the original publication such as genetic and biomarker studies in stored samples. Although such articles often provide important information, they are also often underpowered and only of subspecialist interest. Apart from their scientific value, they offer investigators who played less prominent roles in the original article, the opportunity to publish first-author articles and a wider range of journals the opportunity to get their piece of the cake where the original study has been published in a higher ranking journal.The Systolic Blood Pressure Intervention Trial (SPRINT) [1] is clearly a landmark trial that has already reshaped contemporary blood pressure guidelines [2,3]. Not surprisingly we have read over the last couple of years, a large number of additional analyses deriving from SPRINT, which addressed important issues including outcomes by race and ethnicity; outcomes by baseline DBP; visit-to-visit blood pressure variability; outcomes in people with and without chronic kidney disease; and comparisons with other landmark studies into intensive blood pressure-lowering strategies or treatment of patients at high cardiovascular risk. In the current issue of Journal of Hypertension, we find a particularly important analysis of SPRINT in an article by Foy et al.[4].Foy et al.[4] have studied whether the benefits of intensive SBP lowering extends to both men and women by separately analysing data from male and female SPRINT participants. The authors have shown that the primary composite endpoint was reduced by 16% in women and by 27% in men with no interaction between treatment and sex. The lack of statistical interaction indeed suggests that the overall SPRINT data are not grossly different between men and women.One may argue that a sex-specific subgroup analysis in SPRINT is not necessary. Even if SPRINT did not stratify treatment by sex, men and women were equally represented in the two treatment groups, and the analyses were statistically adjusted for sex. The randomization process and a sufficiently large sample size should indeed guarantee that there are no significant baseline differences between treatment arms. Following this line of argument, however, one would then not only query the importance of the present sex-specific analysis by Foy et al.[4] but also the need for adjustment for sex in the first place.Clearly, adjustment by statistical means cannot take biological variability fully into account. This is particularly true with regard to biological and other differences between men and women that cannot be represented by a binary ‘sex’ variable in statistical analysis. There are biological processes that are specific to women at different stages of their lives that are far more complex than a simple binary variable and include menarche, the contraceptive pill, pregnancy and menopause. Of course, there are also male-specific biological conditions, and features in both sexes that extend beyond the simplistic binary variable and include societal expectations, interaction with peers and other aspects covered by the wider term of gender. There is a growing body of evidence that all of these, affect cardiovascular health [5].In the field of hypertension, numerous differences between men and women have been recognized.

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