In total, 1221 studies through the initial searches in different datasets as potentially relevant literature reports and 1013 were left after duplicates removed. Majority of potentially relevant literatures were excluded by browsing title or abstract. After retrieving 30 full-length manuscripts,finally, 12 articles [7-9, 16, 17, 23-29] of 19 studieswere eligible for data extraction and meta-analysis. The flow chart of the studies recruited in the current study can be found in Figure 1.
19 studies met the inclusion criteria and a total of 21301 were included in the study.Eight studies [7-9, 17, 26-28] addressed the association between sarcopenia and hypertension, and 11 studies [16, 23-25, 29] focused on the association between handgrip strength and hypertension.The included studies were published between 2013 and 2019 and the sample size ranged from 72 to 4771. The study participants’ characteristics of the included studies can be found in Supplementary Table 1 and Supplementary Table 2.
Six studies were conducted in China[16, 17, 26, 29], two in Republic of Korea and Japan , andUnited States [9, 23, 30, 31], one in Turkey, Switzerland , Italy , and Spain . Most of the studies were cross-sectional studies except two cohort studies [7, 9]. The characteristics of the included studies and patients were summarized in Table 1 and Table 2.
Quality assessment of studies
Newcastle-Ottawa Scales for the eligible studies were presented in Supplementary Table 3 and all included studies were found to exhibit a higher quality. Four studies were evaluated as 6 stars, 6 studies were 7 stars, and 2 studies were 8 stars.
The association between sarcopenia and hypertension
All of theeight eligible studiesreported the ORs of hypertension, and the ORs ranged from 0.41 to 4.38. When pooled the ORs together, the summarized ORs was 1.29 (95% CI=1.00-1.67, P=0.04) with a moderate heterogeneity (I2 = 74%). The detailed information could be found in Figure 2 and Supplementary Figure 1.
To explore the sources of heterogeneity, subgroup analysis was performed by categorizing the studies according to the ethnicity of the participants and the Newcastle-Ottawa Scales than were equal to or more than 7 stars.The Asian group included 4 studies from China and Korea, the Caucasian group included four studies conducted in United States, Italy, Spain, and Turkey.The summarized ORs for the Asian group 1.50 (95% CI=1.35-1.67, P=0.00) was significantly higher than that of Caucasian group1.08 (95% CI=0.39-2.97, P=0.88).The heterogeneities for the two subgroups were significantly decreased to I2 = 34% and I2 =40%.When removed the studies that with lower quality (Newcastle-Ottawa Scales<6), the overall OR were 1.53 (95%CI=1.37-1.71, P=0.00) with lower heterogeneity (I2 =2.62%). More data was presented in Figure 3 and Figure 4.
The association between handgrip strength and hypertension
Eleven studies provided the data on association between handgrip strength and hypertension. Ten studies reported the odds ratios and 95% CI. The overall odds ratios and 95% CIwas 0.99 (95% CI=0.80-1.23, P=0.93) with a higher heterogeneity (I2 = 76%) and significant public bias (P<0.01). The detailed data can be found in Figure 5.
As shown in Figure 6 and Figure 7, to explore the sources of heterogeneity and public bias, the included studies were categorized into two groups by the gender of the participants. For the males, the pooled OR was 1.14 (95%CI=0.91-1.43, P=0.27) with an acceptable heterogeneity (I2 = 31%) and public bias (P>0.05). The fameless group had a slightly lower OR (0.81, 95%CI=0.52-1.26,P=0.34, I2 = 45%) without public bias (P>0.05).
Seven studies reported the β value and stand error of the linear regression on hypertension and the pooled β value was -1.57 with an SE equal to 1.03, and the heterogeneity was 99%. As two studies provided the data on different body mass indexes, two more subgroup analysis were done, underweight or normal body mass index group (OR=1.04, 95%CI=0.81-1.33, P=0.77), overweight or obese body mass index group (OR=1.18, 95%CI=0.94-1.41, P=0.16). The data was presented in Supplementary Figure 3 and Supplementary Figure 4.
Most of the analysis except one was found potential publication bias among the included trials according to Begg rank correlation analysis and Egger weighted regression analysis (P value of the analysis was more than 0.05). For the analysis with public bias, when grouped the studies by the gender of the participants, the public bias was disappeared (P>0.05, Figure 6 and Figure 7). The detailed potential publication bias of each analysis can be found in Supplementary Table 4