Abstract
To determine quantitative differences between weight loss and changes in clinic blood pressure (BP) and ambulatory BP in patients with obesity or overweight, the authors performed a meta-analysis. PubMed, Embase, and Scopus databases were searched up to June 2022. Studies that compared clinic or ambulatory BP with weight loss were included. A random effect model was applied to pool the differences between clinic BP and ambulatory BP. Thirty-five studies, for a total of 3219 patients were included in this meta-analysis. The clinic systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly reduced by 5.79 mmHg (95% CI, 3.54-8.05) and 3.36 mmHg (95% CI, 1.93-4.75) after a mean body mass index (BMI) reduction of 2.27 kg/m², and the SBP and DBP were significantly reduced by 6.65 mmHg (95% CI, 5.16-8.14) and 3.63 mmHg (95% CI, 2.03-5.24) after a mean BMI reduction of 4.12 kg/m². The BP reductions were much larger in patients with a BMI decrease ≥3 kg/m² than in patients with less BMI decrease, both for clinic SBP [8.54 mmHg (95% CI, 4.62-12.47)] versus [3.83 mmHg (95% CI, 1.22-6.45)] and clinic DBP [3.45 mmHg (95% CI, 1.59-5.30)] versus [3.15 mmHg (95% CI, 1.21–5.10)]. The significant reduction of the clinic and ambulatory BP followed the weight loss, and this phenomenon could be more notable after medical intervention and a larger weight loss.
Generated Summary
A systematic literature search was conducted to identify relevant studies in the PubMed, Embase, and Scopus databases up to June 2022 to determine quantitative differences between weight loss and changes in clinic blood pressure (BP) and ambulatory BP in patients with obesity or overweight. Only English-language studies were included. The specific keywords and search strategies were presented in the Supplementary Appendix. In addition, the reference lists of included studies were also checked to identify relevant studies. After identifying relevant articles, two reviewers extracted the data independently and the disagreements were resolved through discussion. The following data were extracted: study characteristics (authors, year of publication, journal, country/region, study design), baseline information of participants (sample size, mean age, sex, hypertensive status, weight, and BMI), BP measurement (methods and devices of BP measurement contain at clinic or mean 24-h ambulatory), mean values and SD of clinic and ambulatory BP measurement between weight loss before and after. A random-effect model was used and the results were reported as MDs of BP values. Heterogeneity was estimated by a Q test (p < .1) and I2 statistic, with I2 values of 25, 50, and 75% representing mild, moderate, and severe heterogeneity, respectively. Besides, a subgroup analysis was performed by the percent of BMI reduction, initial BMI values, intervention modalities, sex, and the percent of weight reduction. All statistical analyses were performed using Revman 5 (The Cochrane Collaboration, The Nordic Cochrane Centre, Copenhagen, Denmark) and Stata 12 (StataCorp, College Station, Texas).
Key Findings & Statistics
- The clinic SBP and DBP were significantly reduced by 5.79 mmHg (95% CI, 3.54-8.05) and 3.36 mmHg (95% CI, 1.93-4.75) after a mean body mass index (BMI) reduction of 2.27 kg/m², and the SBP and DBP were significantly reduced by 6.65 mmHg (95% CI, 5.16-8.14) and 3.63 mmHg (95% CI, 2.03-5.24) after a mean BMI reduction of 4.12 kg/m².
- The BP reductions were much larger in patients with a BMI decrease ≥3 kg/m² than in patients with less BMI decrease, both for clinic SBP [8.54 mmHg (95% CI, 4.62-12.47)] versus [3.83 mmHg (95% CI, 1.22-6.45)] and clinic DBP [3.45 mmHg (95% CI, 1.59-5.30)] versus [3.15 mmHg (95% CI, 1.21–5.10)].
- Nineteen studies, including a total of 2428 patients, compared clinic SBP before and after weight loss and eighteen studies included 2307 patients compared clinic DBP. The clinic SBP and DBP were significantly reduced by 5.79 mmHg (95% CI, 3.54-8.05) and 3.36 mmHg (95% CI, 1.93-4.75) after a mean BMI reduction of 2.27 kg/m².
- However, there were significant statistical heterogeneities among included studies (12 = 91%, p<.01 for SBP; I2 = 88%, p<.01 for DBP).
- Twenty-two studies, including a total of 1072 patients, compared ambulatory SBP and DBP with weight loss. The mean ambulatory SBP and DBP values were significantly reduced by 6.65 mmHg (95% CI, 5.16-8.14) and 3.63 mmHg (95% CI, 2.03-5.24).
- Studies including daytime and night-time BP indicate that the mean daytime and night-time ambulatory SBP values were reduced by 4.43 and 4.40 mmHg, meanwhile, the mean daytime and night-time ambulatory DBP values were reduced by 3.70 and 1.91 mmHg. The statistical heterogeneities were also significant (12 = 90%, p<.01 for SBP; 12 = 98%, p<.01 for DBP).
- The MDs between clinic and ambulatory SBP in patients with medical interventions were 7.72 mmHg (95% CI, 4.53-10.91) and 8.34 mmHg (95% CI, 5.56-11.12), respectively, which were much larger in subgroups with males more than 50% males than in subgroups with less than 50% males.
- Eight studies, including a total of 409 patients, compared ambulatory SBP before and after weight loss and 12 studies that included 620 patients compared ambulatory DBP showed that medical interventions were more efficient than lifestyle interventions.
- The clinic DBP reductions in patients with medical interventions [2.97 mmHg (95% CI, 0.13-5.81)] were lower than patients with lifestyle interventions [3.57 mmHg (95% CI, 1.66-5.48)] in this study, showed that lifestyle intervention may have potential benefits over medical intervention.
Other Important Findings
- In 2017, the Global Burden of Disease Obesity Collaborators revealed that more than 603.7 million adult individuals were obese and high BMI accounted for 4.0 million deaths worldwide.
- In China the prevalence of overweight (BMI 24.0-28.0 kg/m²) and obesity (BMI ≥28.0 kg/m²) might reach 65.3% in adults.
- Obesity is a risk factor for hypertension and several cardiovascular diseases.
- The Global Burden of Disease Obesity Collaborators also estimated that more than two-thirds of deaths related to high BMI were due to cardiovascular disease.
- The mean daytime and night-time ambulatory SBP values were reduced by 4.43 and 4.40 mmHg, meanwhile, the mean daytime and night-time ambulatory DBP values were reduced by 3.70 and 1.91 mmHg.
- In studies with both clinic BP and ambulatory BP, clinic BP decreased more than ambulatory BP, whether systolic or diastolic.
Limitations Noted in the Document
- The overall quality of the evidence of the analyzed data, based on the GRADE approach, is low to moderate, which is summarized in Table S2.
- We had to downgrade the quality of evidence for all outcomes because of the substantial and considerable heterogeneity of the results.
- For two outcomes (before weight loss vs. after weight loss), indirectness was identified because the mean BMI and BP values of the baseline population of several studies differed from those of all others.
- Serious imprecision was indicated by the wide Cls of various results.
- The published protocol did not include sufficiently detailed data reporting and statistical analysis methods.
- Sixteen studies have not illustrated whether they enrolled patients consecutively or randomly.
- The timing and blinding information of clinic and ambulatory BP measurements were also poorly reported.
Conclusion
The main findings of the present meta-analysis are that: (1) the mean clinic and ambulatory SBP differences between weight loss were 5.79 mmHg (95% CI, 3.54-8.05) and 6.65 mmHg (95% CI, 5.16-8.14), respectively, which were much larger in subgroups with males more than 50% males than in subgroups with less than 50% males; (2) the MDs between clinic and ambulatory SBP in patients with medical interventions were 7.72 mmHg (95% CI, 4.53-10.91) and 8.34 mmHg (95% CI, 5.56-11.12), respectively, which were much larger in subgroups with males more than 50% males than in subgroups with less than 50% males; (3) in studies with both clinic BP and ambulatory BP, clinic BP decreased more than ambulatory BP, whether systolic or diastolic. Based on office BP, the global prevalence of hypertension was estimated to be 1.13 billion in 2015. Hypertension is a major risk factor for stroke, atherosclerosis, and other cardiovascular diseases, and obesity is a major risk factor for hypertension. On the other hand, patients with hypertension are also frequently overweight or obese presenting a vicious circle, in which weight gain progressively increases as a consequence of hypertension and it also further aggravates the severity of the BP. Obesity is a known independent risk factor for hypertension. Excessive weight gain is associated with hypertension. However, the magnitude and the direction of the association tend to differ on the level of economic development, sex, and race. Women tend to have a higher proportion of body fat stored in subcutaneous rather than visceral adipose tissue because of the differences in body composition between men and women. At the same BMI, women will tend to have a considerably higher percentage of body fat than men, that may explain why the sex subtype has different outcomes. A meta-analysis showed that the mean SBP and DBP reductions were associated with an average weight loss, but weight ignores the effects of height, waistline, and body fat percentage, BMI has a more accurate predictive effect. Ambulatory BP monitoring provides the average of BP readings over a defined period and offers several advantages, such as stronger prognostic evidence and measurements in real-life settings, numerous studies have used ambulatory BP to improve the accuracy of BP measurements. Our results are especially important because we cite ambulatory BP data from related studies and compare them with the clinic BP data. In our study, clinic BP decreased more than ambulatory BP, whether for systolic or diastolic readings. The greater fall in office BP in patients with severely elevated pretreatment BP is caused to a large extent by the reduction of the white coat effect. Because 24-h ABP is void of white coat and the placebo effect, the changes in ABP are smaller and the pretreatment BP level lower thereby explaining at least in part why changes in office BP and ambulatory BP are not related to each other in a 1:1 fashion. There are many things in common between the treatment of obesity and hypertension, such as lifestyle and diet changes.