J Clin Hypertens. 2018;20:613. wileyonlinelibrary.com/journal/jch
©2018 Wiley Periodicals, Inc.
LETTER TO THE EDITOR
Association between duration of oral contraceptive use and
risk of hypertension: A meta- analysis, methodological and
To the Editor
I read the study conducted by Liu et al
that was published in the
Journal of Clinical Hypertension. The authors tried to evaluate the
effect of oral contraceptive duration on hypertension risk, as well as
assess the possible dose- response relationship between oral contra-
ceptive duration and hypertension risk. I think some issues on meth-
odological pattern needs to be considered.
First, the study selection and characteristics has been reported by
Figure 1. Of total 6227 retrieved reported articles (6222: left box and
5: right box), 5922 articles were excluded. Therefore, 305 articles is
expected to be considered for abstract screening; however, this was
3266. Moreover, considering eligibility box, even if we accept 25 full
text articles remains for named section, after excluding 16 articles
(third exclusion box on right side), the number of eligible articles for
final meta- analysis reaches to 9. While 17 full articles were selected.
Second, Table 1 shows detailed characteristics of the included
studies, but unfortunately there are egregious errors. For example, for
the first study in the list, which was published by Chiu et al
lowing comments needs to be addressed:
• The total past oral contraceptive users sample size of the referenced
study was (25 780; 48-58 years = 10 647; 58-66 years = 9213; and
by Liu et al
• Authors abbreviate NA (not available) for “adjustment for covariate”
part, while in the referenced study, authors clearly mentioned “odds
ratios were adjusted for demographic and lifestyle factors that were
significantly associated with treatment for high blood pressure in
univariate analysis. Namely, income, country of origin, BMI, smok-
ing, alcohol, exercise, family history of high blood pressure, meno-
pausal hormone therapy use, number of children, whether they
breastfed, and age of menopause, with additional categories for
missing values (see page 5, methods).
• The reported adjusted OR (odds ratio) in the main article for
eachagecategorywas(48-58years,1.1;58-66years,0.9; and ≥
67 years, 0.9), which is different from the one in Liu et al
Third, the Homogenization methodology of reported OR, hazard
ratio (HR) or relative risks (RR) of different studies was not described. The
same errors were also detected in other reported studies.
Considering these points; which have direct effect on the final
conclusion, are important.
CONFLICT OF INTEREST
The author reports no conflicts of interest.
Samaneh Asgari http://orcid.org/0000-0002-7032-310X
Samaneh Asgari Msc
Prevention of Metabolic Disorders Research Center, Research Institute
for Endocrine Sciences (RIES), Shahid Beheshti University of Medical
Sciences, Tehran, Iran
1. Liu H, Yao J, Wang W, Zhang D. Association between duration of oral
contraceptive use and risk of hypertension: a meta- analysis. J Clin
2. Chiu CL, Lind JM. Past oral contraceptive use and self- reported
high blood pressure in postmenopausal women. BMC Public Health.