Reviewer's report
Title:Educational level, prevalence of hysterectomy, and age at amenorrhoea: a
cross-sectional analysis of 9536 women from six population-based cohort studies
in Germany.
Version:2Date:1 November 2013
Reviewer: Rachel Cooper
Reviewer's report:
This well written paper examines the association between educational level and
hysterectomy in a large sample of German women drawn together from six
population based cohort studies.
The authors are to be commended for drawing together data from different
sources and performing comparable analyses across each of these studies.
Socioeconomic differences in hysterectomy have previously been described in a
number of other studies, some of which have been able to explore time to event,
and so the findings presented are largely confirmatory.
Overall assessment
The question posed by the authors is well defined (although please see
comments below about the need to justify the investigation of differences
between East and West Germany and the value of including an investigation of
differences in age at amenorrhea).
The methods appear to be appropriate and are well described and the data
appear to be sound.
The discussion and conclusions are well balanced and adequately supported by
the data and most of the main limitations of the work are clearly stated. The
authors clearly acknowledge the work upon which they are building in their
discussion of existing literature. The title and abstract accurately convey what
has been found and the paper is well written.
Major compulsory revisions:
1) The authors provide a nice description in their discussion of why differences
between East and West Germany may be expected. However, please could the
justification for examining differences between West and East Germany be
introduced in the background section.
2) The authors appear to have included only age and study as covariates in their
analyses. Was there any possibility to include other potentially important
covariates such as parity and to investigate some of the pathways that are
proposed as potential explanations of the findings? If not, please consider the
limitations of this in the discussion.
3) Without data on time to event it is not possible for the authors to establish
whether among the older women (among whom an association between
education and hysterectomy was not found) an association between educational
level and hysterectomy did exist at younger ages but has been diluted by the lack
of an association between education and hysterectomy performed at older ages.
Changes in association with age at hysterectomy have been shown in a previous
study; in one of our British studies cited, lower educational level was strongly
associated with higher rates of hysterectomy up to age 44 years but not with
hysterectomies between ages 44 and 57 years (the end of follow-up) (Cooper et
al. BJOG 2005;112:1126-33) – the association of education with early
hysterectomy may not have been detected in this study if all hysterectomies had
been grouped together. The authors should consider mentioning in their
discussion the possibility that the lack of association between education and
hysterectomy in the oldest age group could be explained by changes in
association with age, alongside their suggestion that it could be explained by a
cohort effect. Changes with age (within a specific cohort) in the types of
gynaecological disorders experienced and the desire to preserve fertility, and the
educational gradients in these factors, may explain differences in association
between education and hysterectomy by age of procedure.
4) The authors have considered a number of possible explanations of the
associations found between education and hysterectomy. Related to points 2 and
3, the potentially important role of parity and age at completing desired family
size should be considered as possible explanations of the associations found.
For example, women with lower educational level tend to have higher parity and
so be at greater risk of those gynaecological disorders that may occur as a
consequence of child bearing. Further, women with higher educational levels
tend to have children at older ages than women of lower educational level and so
may not achieve their desired family size until later ages whereby even if
experiencing gynaecological problems they may be more likely to choose (or be
offered) less invasive treatments which preserve their fertility for longer than
women with lower educational levels.
5) It is already well documented that average age at hysterectomy is lower than
average age at natural menopause. It is therefore unclear why the authors have
chosen to make the study of age at amenorrhoea one of the objectives of this
study especially as it could not be examined across all of the included studies.
This may distract readers from the main focus of the paper and I would suggest
removing it.
Minor essential revisions:
1) Please indicate in the abstract, the footnote to figure 3 and the appropriate
column in table 1 that the range of educational level 1-8 goes from lowest to
highest.
Discretionary revisions:
1) The authors need to consider the possibility that higher rates of hysterectomy
in some areas than others, which have similar expected rates of gynaecological
morbidity, could indicate that there is a need for surgery that is not being met in
some areas (due to under-utilisation of surgery) as well as the converse.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a statistician.
Declaration of competing interests:
I declare that I have no competing interests.