Mediator or moderator? The role of obesity in the association between age at menarche and blood pressure in middle-aged and elderly Chinese: a population-based cross-sectional study

Objective We investigated the moderation/mediation between the age of menarche and obesity parameters in predicting blood pressure (BP) in middle-aged and elderly Chinese. Design Our study is a population-based cross-sectional study. Setting Participants in this study came from the China Health and Retirement Longitudinal Study (CHARLS). Participants The analytical sample included 4513 participants aged 45–96 years. Main outcome measurements Data were selected from the CHARLS, a cross-sectional study. Between-group differences were evaluated using χ2, t-test and one-way analysis of variance. The trend of related variables by characteristics was also tested using contrast analysis, as appropriate. Then, correlations between characteristics, moderator, mediator, and independent and dependent variables were used by Spearman’s correlation test and Pearson’s correlation test. Finally, the mediation analysis was performed by model 4 in PROCESS V3.3 macro for SSPSS, and moderation analysis was used by model 1 for assessment. All covariates were adjusted in the moderation or mediation models. Results In the correlation analysis, body mass index (BMI) and waist circle (WC) level were positively correlated with both systolic blood pressure (SBP) and diastolic blood pressure (DBP) in women (BMI and DBP: r=0.221, p<0.001; WC and DBP: r=0.183, p<0.001; BMI and SBP: r=0.129, p<0.001; WC and SBP: r=0.177, p<0.001). Age of menarche was negatively correlated with DBP (r=−0.060, p<0.001). However, the age of menarche was not significantly correlated with SBP (r=−0.014, p=0.335). In the moderator analysis, after controlling for the potential confounders, the interaction term of obesity parameters×age of menarche was not significant for predicting either DBP (BMI: B=0.0260, SE=0.0229, p=0.2556, 95% CI −0.0189 to 0.071; WC: B=0.0099, SE=0.0074, p=0.1833, 95% CI −0.0047 to 0.0244) or SBP (BMI: B=0.0091, SE=0.0504, p=0.8561, 95% CI −0.0897 to 0.108; WC: B=−0.0032, SE=0.0159, p=0.8427, 95% CI −0.0343 to 0.028). All correlations were significant correlation between age of menarche, obesity parameters and BP except the path of the menarche age→SBP (with the addition of the BMI indicator: β=−0.0004, B=−0.0046, p=0.9797, 95% CI −0.3619 to 0.3526; with the addition of the WC indicator: β=0.0004, B=0.0044, p=0.9804, 95% CI −0.3439 to 0.3526) in crude model. In general, after controlling for potential confounders, BMI (DBP: β=−0.0471, B= −0.2682, p=0.0021, 95% CI −0.4388 to –0.0976; SBP: β=−0.0515, B=−0.6314, p<0.001, 95% CI −0.9889 to –0.2739) and WC (DBP: β=−0.0474, B= −0.2689, p<0.001, 95% CI −0.4395 to –0.0984; SBP: β=−0.0524, B=−0.6320, p<0.001, 95% CI −0.9832 to –0.2807) partly mediated the relationship between age of menarche and BP. Conclusions The interaction term of obesity parameters×age of menarche was not significant for predicting either DBP or SBP in women. Moreover, obesity parameters partly mediated the relationship between the age of menarche and BP.

2. Ethical approval and Informed consent were not mentioned in the Method Section. 3. What was the measurement method of blood pressure, various measurement by various personnel? This can be discussed as a limitation of this study. 4. What was the method of height measurement, particularly in elderly women who might have kyphoscoliosis? Was the height measured or just self-reported? 5. There were wrong spelling words such as HCL-C (page 9), studier (page 17). 6. The descriptive legends of Tables 1, 2 and 3 were the same!!! The authors should be careful for these details VERSION 1 -AUTHOR RESPONSE Reviewer: 1

Dr. Basma Al-Ahmad, International Islamic University Malaysia
Comments to the Author: 1. To enhance the importance of the manuscript, the authors are advised to justify the merit of the study.
Response: thank you very much, we have revised the discussion, and added the strength to the study.
There were several limitations to the study. The main limitations of our research are related to the cross-sectional study and the self-reported method used for the assessment of age at menarche and most related confounders. Blood pressure in our study was measured at home by professionally trained volunteers, and the next step is the use of clinical blood pressure and ambulatory blood pressure. However, this is the first large population study to examine the moderation between the age of menarche and obesity parameters in predicting blood pressure (BP) in middle-aged and elderly Chinese, as well as the mediation effects of obesity parameters on the relationship between age of menarche and BP. Moreover, a significant strength of the study is a large sample of 4513 middleaged and older Chinese. The results provided baseline data that could be explored further in future prospective studies.
2. To improve the validity of the statistical analysis, the authors are requested to show how the sample size was determined.
Response: thank you very much, we have revised the sample size.

Individuals
The Individuals of the study were selected from the China Health and Retirement Longitudinal Study (CHARLS), Wave 1 (2011). At baseline, 6883 women were recruited for a longitudinal study, 1875 individuals were excluded because the absence of metabolic measures, a group of 41 participants did not have medication history, and 65 individuals did not have their blood pressure, 389 individuals used antihypertension drugs. Finally, 4513 individuals were included in the analyses. Figure 1 summarized the selection of participants. Our study involved 4513 individuals aged 45 years were total women [mean ± standard deviation age=58.59 ± 9.31years, ranged from 45 to 96years]. The mean and standard deviation of menarche age were 16.27±2.18 years (ranged from 10 to 30 years).
3. The research methods were appropriately conducted. However, some parts of the methodology are not fully described and need further explanation.( like the lipid profile measurement , did you measure the ratio of LDL to HDL ? if you did please add it to the results ) Response: thank you very much, we have added the LDL-C/HDL-C to the result, thanks again.  Response: thank you very much, it was typo. It is HDL-C, and we have corrected the error. Thanks again.
5. page 19,20 Discussion : please add further discussion and explanation about the relation between woman with higher age of menarche with the changes in the lipid and blood pressure that you already highlight in the results page 11 line 25,26.
Response: thank you very much, we have revised the discussion, and added further discussion and explanation about the relation.
We also found a significantly negative relationship between age at menarche and BP in mid-aged and elderly Chinese women. However, this association did not exist between the age of menarche and SBP before adjusting the related confounders. This result consistent with previous findings regarding the age of menarche as a cardiovascular risk factor. The weak association between age at menarche and BP in adulthood could, in part, be explained by the fact that early matures were younger than women with late menarche. This result could be an expression of the fact that BP is an outcome with a higher latency period than obesity. Moreover, among women who already entered menopause in our study, the effects of menarche could be even weaker, as results suggest, and obesity could have more effect on BP. We also found that women with a higher age of menarche had higher HDL-C level but had lower DBP levels. were potential mediators to target when interventions for BP control and management.

Comments to the Author:
This cross-sectional study included 4513 Chinese women, aged 45-96, recruited from the Chinese Health and Retirement longitudinal Study. The objective of this study was to determine the correlation/interaction of the age at menarche, BMI and hypertension in elderly age group, using moderator analysis and mediator analysis. The results showed that obesity parameters and age at menarche were not significant to predict hypertension, but obesity was partly related to the age at menarche and diastolic hypertension.  Figure 1 summarized the selection of participants. Our study involved 4513 individuals aged45 years were total women [mean ± standard deviation age=58.59 ± 9.31years, ranged from 45 to 96years]. The mean and standard deviation of menarche age were 16.27±2.18 years (ranged from 10 to 30 years).

2.
Ethical approval and Informed consent were not mentioned in the Method Section.
Response: thank you very much, we have revised the related content in the method section, thanks again.

individuals used antihypertension drugs
Response: thank you very much. Blood pressure in our study was measured at home by professionally trained volunteers. The average value of blood pressure was measured by the mean of the 3-time measurements. Performance measurements available in order to help decision makers choose the right ones for their specific purposes. There are usually three ways to measure blood pressure, Family self-test blood pressure, clinical blood pressure, and ambulatory blood pressure.
And ambulatory blood pressure is the most accurate. However, the blood pressure measurement in our study is suitable for large-scale epidemiological investigation, and we add the limitation in our study.

4.
What was the method of height measurement, particularly in elderly women who might have? Was the height measured or just self-reported?
Response: thank you very much, we have detailed the method of height measurement. The method was used in our previous study [23]. Thanks again.
Height was measured using a height measurement instrument (Omron hem-7200 sphygmomanometer). Participants were asked to stand barefoot on the base plate of the height meter in the upright position, with the back against the vertical back plate of the measuring instrument, with eyes open, arms alongside the body and heels were closed and the toes were separated by 60 degrees. Anyone who appeared to unable to complete measurement in time due to health reasons such as hunchback and inability to stand was excluded from our study. The method was used in our previous study [23].
Response: thank you very much, it was typo. It is HDL-C, and we have corrected the error. Thanks again.
6. The descriptive legends of Tables 1, 2 and 3 were the same!!! The authors should be careful for these details Response: thank you very much, we have revised the legends of Tables, thanks again.

Al-Ahmad, Basma
International Islamic University Malaysia, fundamental dental and medical basic medical science REVIEW RETURNED 20-Dec-2021

GENERAL COMMENTS
The author already follow all the instructions and did all the requested changes that have been send to him previously, changes have been done accordingly REVIEWER Jaruratanasirikul, Somchit Prince Songkla Univ, Pediatrics REVIEW RETURNED 09-Dec-2021

GENERAL COMMENTS
The revised version of this manuscript is now much improved. There are still some minor mistakes on Page 8. , 6883 women were recruited for a longitudinal study, 2370 individuals were excluded (i.e., absence of metabolic measures, and/or absence of medication history, and/or having no blood pressure, and/or using antihypertension drugs). Finally, 4513 individuals were included in the analyses. Figure 1 summarized the selection of participants. Our study involved 4513 participants aged 45 years were total women [mean ± standard deviation age=58.59 ± 9.31years, ranged from 45 to 96years]. The mean and standard deviation of menarche age were 16.27±2.18 years (ranged from 10 to 30 years).
2. Measurement, Omron hem-7200 is the instrument for BP measurement, not height measurement. This instrument should be moved to For height measurement, should it be Stadiometer? Response: thank you very much, we have revised the mistakes. The average value of BP was measured by the mean of the 3-time measurements using Omron hem-7200 sphygmomanometer. Height was measured by height measurement instrument. Participants were asked to stand barefoot on the base plate of the height meter in the upright position, with the back against the vertical backplate of the measuring instrument, with eyes open, arms alongside the body and heels were closed and the toes were separated by 60 degrees. Anyone who appeared to unable to complete measurement in time due to health reasons such as hunchback and inability to stand was excluded from our study. The method was used in our previous study [29].