Title: The impact of sex on blood pressure and anthropometry trajectories from early adulthood
in a Nigerian population: insights into women’s cardiovascular disease risk across the lifespan.
Version: 1 Date: 31 Dec 2021
Reviewer:  Dexter Canoy
Reviewer's report:
This study compares the relationship of age and blood pressure between men and women in a
Nigerian population. The investigators examined within age groups differences in blood pressure
between the sexes across a wide range of ages, and described age-related patterns of blood
pressure phenotypes, as well as body size measures, in men and women.
Comments:
1. Introduction
It is very long. Whilst the first paragraph provides the wider context of the research, focusing
on the main thesis of this research should be preferred. I suggest to reduce the first paragraph to
around one to two sentences (something similar to the first paragraph in the discussion section).
Considering there are several studies looking into this topic, I’d rather that the authors focus on
describing why do this study in this population (Lack of data in African or Nigerian population?
Existing data are not contemporary? Other specific factors why it is worth revisiting this
question?). The authors need to convince readers why this specific research is worth conducting
(beyond answering questions broadly around  cardiovascular risk differences between men and
women).
2. Methods
There are many missing elements in the methods section. One needs to describe, even if briefly,
the study population (who are they, how were they identified and recruited, etc). The authors
refer to this work as a sub-analysis. But what was the main analysis? How were measurements
taken? The WHO STEPwise approach is a useful guideline for monitoring risk factors in the
population. But a description of how this approach was conducted in this specific study should be
provided. How were the blood pressure and body sizes measured? What about other covariables?
Why are they not assessed or considered in this study?
The study design does not say the type of study – one only encounters the fact that this is a
cross-sectional study in the limitation section. It would be better to make this clear early on
when describing the study in the methods section. Since this is a cross-sectional study, I do not
understand why the title (and in the text) implies that blood pressure and body size trajectories
will be described. I would have thought that ‘trajectory’ analyses involve using longitudinally
collected data. I suggest that the description of the study design should be very specific to help
avoid readers to misinterpret the findings.
The statistical approaches, whilst broadly appropriate for simple descriptive analysis, there are
better analytical approaches that could have been used, such as using regression models.
3. Results
The descriptive epidemiology looks broadly appropriate. However, when comparing sex
differences in the findings, one would expect that analyses will take into account other factors
or variables. Unfortunately, most of the key findings are based no crude analysis. Correlations
have limited use in this context. Regression models (or, to an extent, ANOVA) that include
terms for potential confounders are better analytical tools to compare, for example, differences
in blood pressure between men and women at different age categories. Regression can also be
used to describe the relationship of blood pressure and anthropometry  across the ages, and even
describe the non-linear association using regression splines.
4. Discussion
A large proportion in the discussion section is somewhat tangential from the main focus of this
manuscript. What might be more useful approach is to describe how these results compare to
other populations (Western populations, other African populations, or even previous data from
Nigerian population if they exist), considering potential differences in time periods when these
data are collected. Is the study population large enough? Some age groups are too small – for
example, in the older age group, mean systolic blood pressure are widely different between men
and women (ie, the magnitude is of clinical relevance), but the numbers are small and probably
lacking in statistical power.