Abstract
Women are underrepresented in groups of patients seeking hypertension care in India. The present paper reports trends in office and ambulatory blood pressure measurement (OBPM, ABPM) and 24‐h heart rate (HR) with sex in 14,977 subjects untreated for hypertension (aged 47.3 ± 13.9 years, males 69.4%) visiting primary care physicians. Results showed that, for systolic blood pressure (SBP), females had lower daytime ABPM (131 ± 16 vs. 133 ± 14 mm Hg, P < .001) but higher nighttime ABPM (122 ± 18 vs. 121 ± 16 mm Hg, P < .001) than males. Females had higher HR than men at daytime (80 ± 11 vs 79 ± 11.5 bpm) and nighttime (71 ± 11 vs 69 ± 11), respectively (all P < .001). Dipping percentages for SBP (7.4 ± 7.3 vs 9.3 ± 7.4%), DBP (10.1 ± 8.6 vs. 12.3 ± 8.9%), and HR (10.7 ± 7.9 vs. 12.8 ± 9.2%) were lower (P < .001) for females than for males, respectively. Females more often had isolated nighttime hypertension as compared to males (14.9%, n = 684% vs 10.6%, n = 1105; P < .001). BP patterns and HR showed clear differences in sex, particularly at nighttime. As females were more often affected by non‐dipping and elevated nighttime SBP and HR than males, they should receive ABPM, at least, as frequently as men to document higher risk necessitating treatment.
Keywords: ambulatory blood pressure measurement, hypertension management, India, isolated nighttime hypertension, masked hypertension, office blood pressure measurement, white coat hypertension
1. INTRODUCTION
India seems to be affected by sex discrimination in access to health care in particular for visiting tertiary care centers. 1 The latter might be partly related to the fact that there is a general assumption that women are more protected for cardiovascular risk than men and that females may be less affected by high blood pressure (BP), which is not true. 2 This may lead to incorrect assumptions due to lack of data in the Indian population.
Since ambulatory BP measurement (ABPM) is rarely performed, there is not much known about differences in BP patterns related to sex in India. Recently, an initiative was taken to facilitate ABPM by primary care physicians supervised by a group of cardiologists of India.
ABPM has the additional advantage that the heart rate (HR) is also measured during the 24‐hour period. As (nighttime) heart rate is related to cardiovascular risk 3 and there are indications that South Asians have higher heart rate than Europeans, 4 this deserves further investigation.
The present study aims at investigating sex‐related differences in BP and HR pattern in an Indian all comers’ population visiting primary care physicians and who were assigned to undergo ABPM by their physician. Given that men were more often referred to ABPM than women, we hypothesized that, in the present study, men would have higher BP on ABPM and carry a higher cardiovascular risk than women.
Since antihypertensive treatment may significantly influence both subject's BP and HR values during the 24‐hour monitoring period, only subjects not treated for hypertension were selected for the analysis.
2. METHODS
Data from a total of 14 977 untreated subjects attending 574 primary care clinics spread throughout India were analyzed in the present study. All patients were included between January 2017 and November 2018. The study subjects were selected from an existing database because they did not receive antihypertensive treatment. The methods and selection criteria of that database have been explained previously. 5 , 6 In brief, office BP measurement (OBPM) in the physician's office was performed as usual with the BP instrument of the physician's choice (mercury, aneroid, or oscillometric). If the physician considered there was a need for ABPM, this was performed within 7 days after the clinic visit. ABPM was performed according to standard instructions using validated 24‐h ABPM devices (Meditech, Meditech Ltd., Hungary, 7 or WatchBP O3, Microlife, Corporation Taiwan 8 , 9 ). Measurement interval times were set at 20‐min intervals for 24 hours. Daytime and nighttime averages were based on patient's diaries. Patient characteristics and specific cardiovascular risk factors were registered. Both ABPM service and data collection were made available by the sponsor (Eris Lifesciences Ltd). Data were analyzed in an anonymized way after authorization was granted by the institutional ethics committee of the Batra Hospital and Medical Research Centre, New Delhi, India, from where the project was coordinated.
2.1. Patient data
Information about the subject's age, sex, height, body weight, and family history for cardiovascular diseases was collected. Also recorded was personal clinical history for cardiovascular diseases (ischemic heart disease, myocardial infarction, heart failure, stroke, peripheral artery disease, or kidney disease), presence and treatment of arterial hypertension, diabetes mellitus, and dyslipidemia. Patients were included if OBPM was performed and ABPM contained 70% or more successful readings and had minimum numbers of 20 daytime measurements and 7 nighttime measurements.
2.2. Statistical analysis
For the present study, patients were separated for sex. Additionally, subjects were classified into 10‐year age categories (deciles): the youngest age‐groups contained subjects of 30 years and below and the oldest age‐group included those older than 80 years leading to 7 decile groups.
2.2.1. Blood pressure categories
BP categorization was based on OBPM and ABPM threshold values as recommended by the European Society of Hypertension guidelines. 10 BP categorization was based on the following threshold values for OBPM and ABPM: elevated (hypertension) OBPM: SBP ≥ 140 mm Hg and/or DBP ≥ 90 mm Hg; elevated 24‐hour ABPM: 24‐hour SBP ≥ 130 and/or DBP ≥ 80 mm Hg; elevated daytime ABPM: daytime SBP ≥ 135 and/or DBP ≥ 85 mm Hg; and elevated nighttime ABPM: SBP ≥ 120 and/or DBP ≥ 70 mm Hg. Subjects were categorized based on OBPM and ABPM in four categories: (a) sustained normotension ([SNT] normal OBPM + normal 24‐hour + normal daytime + nighttime BP), sustained hypertension ([SHT] elevated OBPM + elevated 24‐hour or elevated daytime or nighttime BP), white coat hypertension ([WCH] elevated OBPM + normal 24‐hour + normal daytime + normal nighttime BP), and masked hypertension ([MH] normal OBPM + elevated 24‐hour or elevated daytime or elevated nighttime BP). 11
The relationship with sex and dipping status was verified; dipping pattern (dipper) was determined as follows: When the reduction in the average nighttime SBP or DBP was 10% or more of the mean daytime SBP or DBP, the patient was classified as dipper. When the decrease was 20% or more, the patient was classified as an extreme dipper. When the reduction was <10% with respect to daytime BP, then the subject was a non‐dipper. When the mean nighttime BP was higher than the mean daytime BP, the patient was classified as a reverse dipper (or “riser”). Subjects were separated based on treatment (yes or no) for analysis. We also calculated the decrease in heart rate (HR) during nighttime as compared to daytime HR (HR dipping).
Given the observational nature of the study, no sample size estimation was done. All subjects included for the analysis provided valid data, and thus, no methodology for replacing missing data was implemented. Main demographic and clinical data were summarized by calculating the mean (±SD) in case of continuous variables and the absolute (n) and relative (%) frequency in case of categorical variables. Patient characteristics between sexs were compared using independent‐sample t test or analysis of variance for continuous variables, as appropriate, and chi‐square tests for categorical variables. The relationship between age and HR, age and BP dipping percentages, and HR dipping and BP dipping percentages was assessed using Pearson's correlation analysis. Indices were considered to be correlated if R> 0.3 or R < −0.3, using the “Rule of Thumb for Interpreting the Size of a Correlation Coefficient”. 12 Results were presented in P‐values. A P‐value of <.01 was considered significant. Data analysis was performed using IBM SPSS Statistics version 26 for Windows.
3. RESULTS
A total of 14 977 subjects aged 47.3 ± 13.9 years and untreated for hypertension were included. Characteristics of the 14 977 subjects in total and separated for sex are shown in Table 1. There were less females than males (30.6% vs 69.4%, P < .001). Females were older (49.2 vs 46.5 years), relatively more often severe obese (5.3% vs 3.6%), more often had diabetes mellitus (3.8% vs 3.0%) but were less often dippers (36.6% vs 48.3%; all P < .001). WCH prevalence was similar in both females and males (20.1% vs 19.3%, P = .3) but males more often had MH than females (15.3% vs 13.5%, P < .01). ABPM daytime SBP was lower (131 ± 16 vs. 133 ± 14 mm Hg, P < .001) for females than for males but nighttime SBP was higher (122 ± 18 vs. 121 ± 16 mm Hg, P < .001). At all BP measurements, females had lower diastolic BP values than males. Females had a lower dipping percentage than males for both SBP (7.4 ± 7.3 vs 9.3 ± 7.4%) and DBP (10.1 ± 8.6 vs 12.3 ± 8.9%).
Table 1.
Demographic and clinical data of 14 977 untreated subjects included in the analysis stratified by sex
| Total | Male | Female | |
|---|---|---|---|
| n = 14 977 | n = 10 389 (69.4%) | n = 4,588 (30.6%) | |
| Age, y | 47.3 ± 13.9 | 46.5 ± 14 | 49.2* ± 13.6 |
| Height | 163.1 ± 8.3 | 164.9 ± 8 | 159.0* ± 7.2 |
| Weight | 71.6 ± 11.1 | 73.5 ± 10.5 | 67.3* ± 11.1 |
| BMI (kg/m2) | 27.0 ± 4.2 | 27.1 ± 4 | 26.7* ± 4.6 |
| Obesity (BMI ≥ 30 kg/m2 [n, %]) | 3025 (20.2) | 2096 (20.2) | 929 (20.2) |
| Severe obesity (BMI ≥ 35 kg/m2) | 619 (4.1) | 374 (3.6) | 245* (5.3) |
| Diabetes mellitus (n, %) | 489 (3.3) | 313 (3.0) | 176* (3.8) |
| Dyslipidemia (n, %) | 187 (1.2) | 137 (1.3) | 50 (1.1) |
| Chronic kidney disease | 122 (0.8) | 83 (0.8) | 39 (0.9) |
| Family CVE (n, %) | 516 (3.4) | 377 (3.6) | 139 (3) |
| Family hypertension (n, %) | 1484 (9.9) | 1048 (10.1) | 436 (9.5) |
| Normotension (n, %) a | 3849 (25.7) | 2474 (23.8) | 1375* (30) |
| Hypertension (n, %) a | 5984 (40) | 4314 (41.5) | 1670* (36.4) |
| WCH (n, %) | 2929 (19.6) | 2007 (19.3) | 922 (20.1) |
| MH (n, %) | 2215 (14.8) | 1594 (15.3) | 621* (13.5) |
| Isolated nighttime hypertension (n, %) | 1789 (11.9) | 1105 (10.6) | 684* (14.9) |
| Dipper (>10% based on SBP) | 6697 (44.7) | 5018 (48.3) | 1679 *(36.6) |
| OSBP (mm Hg) | 140 ± 17 | 140 ± 17 | 139 ± 18 |
| ODBP (mm Hg) | 86 ± 12 | 86 ± 12 | 84* ± 12 |
| OHR (bpm) | 82 ± 14 | 82 ± 14 | 84 ± 14 |
| 24‐h SBP (mm Hg) | 129 ± 15 | 129 ± 14 | 128* ± 16 |
| 24‐h DBP (mm Hg) | 78 ± 10 | 79 ± 10 | 76* ± 10 |
| 24‐h HR (bpm) | 76 ± 11 | 76 ± 11 | 77* ± 11 |
| Day SBP (mm Hg) | 132 ± 15 | 133 ± 14 | 131* ± 16 |
| Day DBP (mm Hg) | 81 ± 11 | 82 ± 11 | 79* ± 11 |
| Day HR (bpm) | 80 ± 11 | 79 ± 11 | 80* ± 11 |
| Night SBP (mm Hg) | 121 ± 16 | 121 ± 16 | 122* ± 18 |
| Night DBP (mm Hg) | 72 ± 11 | 72 ± 11 | 70* ± 11 |
| Night HR (bpm) | 70 ± 11 | 69 ± 11 | 71* ± 11 |
| Dip SBP (%) | 8.7 ± 7.4 | 9.3 ± 7.4 | 7.4* ± 7.3 |
| Dip DBP (%) | 11.6 ± 8.9 | 12.3 ± 8.9 | 10.1* ± 8.6 |
| Dip HR (%) | 12.2 ± 8.9 | 12.8 ± 9.2 | 10.7* ± 7.9 |
| WCE SBP (mm Hg) | 11 ± 16 | 11 ± 16 | 11 ± 16 |
| WCE DBP (mm Hg) | 8 ± 11 | 7 ± 11 | 8* ± 11 |
| Office PP (mm Hg) | 54 ± 14 | 54 ± 13 | 55* ± 14 |
| 24‐h PP (mm Hg) | 51 ± 11 | 50 ± 11 | 52* ± 12 |
| Day PP (mm Hg) | 51 ± 11 | 51 ± 11 | 53* ± 12 |
| Night PP (mm Hg) | 49 ± 12 | 49 ± 11 | 51* ± 13 |
| 24‐h SD SBP (mm Hg) | 14 ± 4 | 14 ± 4 | 14 ± 4 |
| 24‐h SD DBP (mm Hg) | 11 ± 3 | 11 ± 3 | 10* ± 3 |
| Daytime SD SBP (mm Hg) | 13 ± 4 | 13 ± 4 | 13 ± 4 |
| Daytime SD DBP (mm Hg) | 9 ± 3 | 9 ± 3 | 10* ± 3 |
| Nighttime SD SBP (mm Hg) | 13 ± 5 | 13 ± 4 | 13 ± 5 |
| Nighttime SD DBP (mm Hg) | 10 ± 3 | 10 ± 3 | 9* ± 3 |
Abbreviations: ABPM, ambulatory blood pressure measurement; BMI, body mass index; bpm, beats per minute; CVE, cardiovascular event; DBP, diastolic blood pressure; HR, heart rate; MH, masked hypertension; OBPM, office blood pressure measurement; OSBP, office systolic blood pressure; SBP, systolic blood pressure; SD, standard deviation; WCE, white coat effect; WCH, white coat hypertension.
Normotension and hypertension are based on both office and ambulatory blood pressure measurement.
Indicates that male and female values are significantly different from each other at P < .01.
3.1. BP values for age and sex
Figure 1 shows an increase in SBP and a decrease in DBP with increasing age in both males and females. Until the age of 50 years old, males had higher daytime SBP (P < .001) than females but this difference disappeared in the age‐group 51 to 60 years (134 ± 15 vs. 132 ± 17, P = .13 mm Hg for males and females, respectively) and remained similar, thereafter. For systolic nighttime values, there are no significant differences between males and females over the age‐groups.
Figure 1.
Graph showing age‐related systolic (A) and diastolic (B) daytime (open symbols) and nighttime (closed symbols) for males (triangles) and females (circles)
Among those younger than 30 years of age, females had higher nighttime DBP values than males (72 ± 14 vs. 68.5 ± 10 mm Hg, P < .001). From the age of 40 years until the age of 70 years, males had significant higher day and nighttime DBP than females; thereafter, the DBP values become similar for both males and females.
3.2. HR related to sex and age
Females had higher HR than men at daytime (80.3 ± 11.2 vs. 79.4 ± 11.5 bpm), nighttime (71.4 ± 10.6 vs. 68.9 ± 10.6 bpm), and over 24 hours (77.4 ± 10.6 vs. 75.9 ± 10.6 bpm), respectively (all P < .001). At nighttime, HR decreased as compared to daytime for both males and females, but this decrease at nighttime was larger for males than for females (−10.5 ± 8.0 vs −8.8 ± 6.8 bpm, P < .001).
Table 2 shows the correlation values of HR indices with ambulatory BP parameters and age, separated for sex. HR dip correlated (r > 0.3) to SBP and DBP dipping for both males and females. For both sexes, although slightly more for males than for females, daytime HR correlated to both daytime and 24‐hour diastolic BP and nighttime HR correlated to nighttime diastolic BP. Systolic ABPM values showed poor correlation to HR. Office HR showed poor correlation with ABPM indices. Age showed a poor but consistent negative correlation with HR dip and day and nighttime HR for both sexs.
Table 2.
Unadjusted correlation of heart rate (HR) indices with ambulatory blood pressure (BP) monitoring measures in the untreated population separated for males (n = 10 389) and females (n = 4588)
| HR dip (%) | Daytime HR (bpm) | Nighttime HR (bpm) | 24‐h HR (bpm) | OBPM HR (bpm) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Male | Female | Male | Female | Male | Female | Male | Female | Male | Female | |
| Dip SBP (%) | 0.42 a | 0.34 a | 0.15 | 0.12 | −0.14 | −0.09 | 0.06 | 0.05 | 0.04 | 0.02 |
| Dip DBP (%) | 0.45 a | 0.37 a | 0.16 | 0.15 | −0.16 | −0.08 | 0.06 | 0.08 | 0.04 | 0.03 |
| SBP daytime (mm Hg) | −0.02 | −0.07 | 0.10 | 0.04 | 0.11 | 0.07 | 0.11 | 0.05 | 0.08 | 0.03 |
| DBP daytime (mm Hg) | 0.18 | 0.16 | 0.36 a | 0.33 a | 0.22 | 0.23 | 0.34 a | 0.31 a | 0.19 | 0.16 |
| SBP nighttime (mm Hg) | −0.27 | −0.24 | −0.01 | −0.03 | 0.18 | 0.11 | 0.05 | 0.02 | 0.04 | 0.01 |
| DBP nighttime (mm Hg) | −0.14 | −0.08 | 0.22 | 0.22 | 0.31 a | 0.26 | 0.26 | 0.24 | 0.15 | 0.13 |
| SBP 24‐h (mm Hg) | −0.12 | −0.13 | 0.07 | 0.01 | 0.14 | 0.09 | 0.10 | 0.04 | 0.07 | 0.02 |
| DBP 24‐h (mm Hg) | 0.08 | 0.09 | 0.33 a | 0.31 a | 0.27 | 0.25 | 0.34 a | 0.30 a | 0.19 | 0.15 |
| Age (years) | −0.28 | −0.18 | −0.22 | −0.28 | −0.03 | −0.16 | −0.17 | −0.26 | −0.15 | −0.15 |
Considered to be correlated (R > 0.3 or R < −0.3) according to the “Rule of Thumb for Interpreting the Size of a Correlation Coefficient”. 12
3.3. Blood pressure and HR dipping related to sex and age
Figure 2 shows the HR dip for groups classified based on dipping percentage for systolic BP. HR dip was higher for males than for females, except in the group of reverse dippers (all P < .001). In all groups, the average HR decreased at night as compared to daytime HR. In both sexs, the nocturnal HR fall was lowest in the group of reverse dippers (4.2 ± 11.1 and 6.0 ± 8.7% for males and females, respectively) and highest in extreme dippers (18.6 ± 8.9 and 14.7 ± 8.7% for males and females, respectively).
Figure 2.
Graph showing the percent of nocturnal heart rate fall as compared to daytime heart rate (heart rate dip) for subjects classified based on systolic blood pressure dip
Overall, males had a higher dipping percentage than females for both SBP (9.3 ± 7.4 vs 7.4 ± 7.3%) and DBP (12.3 ± 8.9 vs 10.1 ± 8.6%) and HR (12.8 ± 9.2 vs 10.7 ± 7.9%), respectively (all P < .001).
As shown in Table 2, dipping percentages decreased with increasing age for both systolic and diastolic BP and heart rate for males (r = −0.17, r = −0.22 and r = −0.28, respectively) and for females (r = −0.14, r =− 0.16 and r = −0.19, respectively).
Figure 3 shows that in the youngest age‐group, males have significantly higher dipping values than females for SBP (9.8 ± 6.8 vs 7.9 ± 6.7%), DBP (14.4 ± 9.1 vs 11.4 ± 8.9%), and HR (16.2 ± 9.7 vs 12.4 ± 8.5%; all P < .001). Both the dipping values and the difference between males and females linearly decline with increasing age. The lowest dipping values are in the oldest age‐group > 80 years with systolic (3.4 ± 8.3 vs 2.7 ± 8.3%; P = 1.0), diastolic (6.1 ± 9.3 vs 2.1 ± 9.6%; P = .27), and HR (6.9 ± 8.0 vs 4.3 ± 11.0%; P = .9) dipping values for males and females, respectively.
Figure 3.
Dipping percentage of systolic and diastolic blood pressure and heart rate per age‐group separated for males (M) and females (F)
3.4. Isolated nighttime hypertension
In total, 1,789 subjects (11.9%) had isolated nighttime hypertension (INH). Overall, females had relatively more often INH than males (14.9%, n = 684% vs 10.6%, n = 1105; P < .001). Of those with INH, 978 (54.7%) had normal OBPM (male: n = 599, 54.2% and female n = 379, 55.4%). Figure 4 shows the INH prevalence categorized in age‐groups and separated for sex; the overall prevalence within each sex is highest (>20%) after the age of 70 years for males and after the age of 60 years for females. However, it is at the age between 30 and 70 years that females significantly more often show INH than males. The lowest INH prevalence for males and females was seen in the age‐groups of 31 to 40 and 41 to 50 years; 7.1% vs 11.4% and 7.4% vs 11.3%, respectively (all P < .001).
Figure 4.
Prevalence values of isolated nighttime hypertension categorized for age‐groups and separated for sex. A significant difference between males and females within each age‐group is presented by ** for P < .001, * for P < .01
4. DISCUSSION
The present paper showed that overall nighttime SBP was higher in females than in males but daytime SBP was higher in males. Therefore, females had lower dipping percentages for SBP and DBP, were less often qualified as dippers, and more often had INH than males (15% vs 11%). Although INH prevalence was lowest between the age of 30 until 50 years, it was still over 10% in females. The average HR in females was higher than in males at both day and nighttime. In addition, the decrease of nighttime HR was lower for females than for males. Until the age of 50 years, males had higher daytime but not nighttime SBP than females. Except for the youngest and oldest age‐groups, DBP was lower for females than for males in all age‐groups. In both sexes, HR decreased at night as compared to daytime HR but this dip was larger in males than in females. The HR dip correlated to both SBP dip and DBP dip. Both day and nighttime HR correlated to DBP but not to SBP values as obtained with ABPM.
The findings of the present study confirm earlier studies of BP related to sex that men have higher BP values at younger age but that this difference decreases at older age (around the age of 60‐70 years). 13 Hypertension prevalence in early adulthood is less in women than in men. After the fifth decade of life, hypertension incidence increases more with age in women than in men so that the hypertension prevalence for women is equal to or greater than for men at the sixth decade. 14 It has been suggested that with the loss of estrogens at menopause, the unopposed effect of androgens in postmenopausal women may contribute to their elevated BP. 15 Estrogen stimulates nitric oxide (NO) production. Thus, loss of estrogen with menopause could play a role in the increased BP in women after menopause. However, estrogen replacement therapy does not decrease BP so that this probably is not the (only) cause that BP is lower in premenopausal women. 15 Unfortunately, the present study does not provide any information about menopause and estrogen replacement therapy so that this could not be investigated. Another reason that women are catching up their BP level with men may be because of increased sympathetic activity, 16 as suggested by the higher HR in females at nighttime.
4.1. Sleep quality
Another explanation for the fact that women more often had INH showed a lower BP dip and HR dip than males might be related to sleep quality. A recent meta‐analysis found a higher risk of insomnia in women compared with men (risk ratio, 1.41; 95% confidence interval, 1.28‐1.55), and this risk increases with increasing age, with women older than 65 years having the highest risk of insomnia. 17 Wearing the ABPM monitor at night might have disturbed sleep more in females than in males. The present study did not evaluate the sleep quality during BP measurement.
4.2. Heart rate
Several studies showed that HR dip and nighttime HR were related to all‐cause mortality and cardiac events. 18 , 19 , 20 The present study showed that females had higher nighttime HR values (71.4 vs. 69.1 bpm) and a lower HR dip (8.2 vs 9.5 bpm) than males, suggesting that females have higher cardiovascular risk than males, although it must be mentioned that some studies showed that this relationship between HR and mortality generally is stronger in men than in women. 21 , 22
Overall, it must be considered that HR as obtained in the office may not be as reliable as HR obtained from 24‐hour ABPM. In the present study, there was poor correlation between ABPM HR and OBPM HR, especially for subjects with WCH (r = 0.2).
The fact that Indians have a high HR in general indicates poor cardiovascular risk and bad physical conditioning. 23 The higher HR for females as compared to males, as shown in the present study, does not necessarily suggest that they perform less exercise but may be related to different responses to exercise. 24
4.3. Isolated nocturnal hypertension
In the present study, subjects with INH had lower BP values for OBPM and daytime ABPM than those without INH, which indicate that INH is also related to lower daytime ABPM which is related to lower cardiovascular risk. Nevertheless, INH is not an innocent phenotype of ABPM. Analysis with data of more than 8000 subjects from the IDACO database showed that INH predicts cardiovascular outcome. During a 10‐year follow‐up time, INH was associated with a higher risk of total mortality (hazard ratio 1.29, P = .045) and all cardiovascular events (hazard ratio 1.38, P = .037). 25
4.4. Strengths and limitations of the study
The strength of the present study lies in the large number of subjects with a wide age distribution so that both sexs and all age‐groups are represented in good numbers. Participating subjects were drug‐naïve so that their BP pattern was not influenced by antihypertensive drugs. Additionally, the participating subjects received both OBPM and ABPM in a short time frame. However, this study should also be seen within the context of its limitations; there were more males than females participating in the present study (68% vs 32%) as already highlighted. This higher male prevalence may have had some influence on the outcome since there were relatively less women in the younger age‐groups than in the older age‐groups. In addition, the study cohort represents a population that was selected by their treating physicians to undergo ABPM, which may have caused a selection bias. For example, ABPM may have been requested because the obtained OBPM values were close to threshold values or not what the physician expected. This could also have had its effect on the sex distribution. If the overall physician's perception is that women in general have lower cardiovascular risk, this may have led to selection bias because only women with a presumed higher risk, and therefore perhaps a higher BP, were selected. Nevertheless, it is a well‐known problem in India that women less often seek health care support than men.
The high number of study participants in the present study leads to the fact that minor differences in BP (eg, 0.9 mm Hg) can lead to significant differences. However, BP cannot be read with such a high level of accuracy so that the fact that it is significant may have low clinical value. Therefore, one should be careful in drawing conclusions from only minor differences in the large population. In order to prevent this interpretation bias in the present study, we, therefore, considered P < .01 as significant instead of the commonly used value of P < .05. Finally, as only drug‐naïve patients were selected, the present study population may not be representative of the elderly population, in particular, as over half the subjects older than 50 years of age have elevated BP or are treated for it. 26
5. CONCLUSIONS
The present study showed a sex‐specific ABPM pattern. Women had more often INH, a lower BP dip and HR dip than men. As nighttime BP is a significant cardiovascular risk predictor, 24‐h ABPM is especially important for women. At younger ages, males had higher BP than females but this changed after menopause. Women had higher HR during day and nighttime and a lower HR dip than men, suggesting a higher risk of all‐cause mortality and cardiovascular events. The finding of the present study showed that females, especially after menopause, had significant differences in ABPM parameters as compared to males suggesting a poorer cardiovascular prognosis. Therefore, we reject the hypothesis that males have higher BP and thus higher cardiovascular risk than females based on ABPM. The underrepresentation of females in the present study and general Indian health care is not justified by lower cardiovascular risk. Indian females must be encouraged to seek medical support earlier, and Indian physicians should be encouraged to assess ABPM equally among their male and female patients.
CONFLICT OF INTEREST
WJV is employed by Microlife.
AUTHOR CONTRIBUTIONS
Upendra Kaul PhD MD, Ajit Bhagwat PhD MD, A K Pancholia PhD MD, Suhas Hardas PhD MD, Neil Bardoloi PhD MD, Deepak Davidson PhD MD, P R Sivakadaksham PhD MD, J C Mohan PhD MD, P R Vaidyanathan PhD MD, S Natarajan PhD MD, L N P Kapardhi PhD MD, K S Reddy PhD MD, Dharmesh Solanki PhD MD, J S Makkar PhD MD, M Viswanathan PhD MD, Priyadarshini Arambam PhD, and Viraj Suvarna PhD MD contributed in the design of the study and collected data. Upendra Kaul PhD MD and Stefano Omboni PhD MD contributed in writing of the paper. Willem J. Verberk PhD contributed in the design of the study, performed the analysis, and wrote the manuscript.
Kaul U, Bhagwat A, Omboni S, et al. Blood pressure and heart rate related to sex in untreated subjects: the India ABPM study. J Clin Hypertens. 2020;22:1154–1162. 10.1111/jch.13894
Funding information
Eris Lifesciences Limited (Ahmedabad, India) provided an ABPM service without charge.
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