Assadi, Majid

Darabi, Hossein

Khajehian, Mohammad Mehdi

Nabipour, Iraj

Ostovar, Afshin

Purbehi, Mohammadreza

Raiesi, Alireza

Vahdat, Katayoun

Bushehr University of Medical Sciences Repository

Hypertension risk and conventional risk factors in a prospective cohortstudy in Iran: The Persian Gulf Healthy Heart Study☆Afshin Ostovar a,⁎, Katayoun Vahdat a, Alireza Raiesi a, Mohammadreza Purbehi a, Hossein Darabi a,Mohammad Mehdi Khajehian a, Majid Assadi b, Iraj Nabipour ca The Persian Gulf Tropical Medicine Research Center, Bushehr University of Medical Sciences, Bushehr, Iranb The Persian Gulf Nuclear Medicine Research Center, Bushehr University of Medical Sciences, Bushehr, Iranc The Persian Gulf Marine Biotechnology Research Center, Bushehr University of Medical Sciences, Bushehr, Irana r t i c l e i n f oArticle history:Received 14 January 2014Accepted 18 January 2014Available online 24 January 2014Keywords:HypertensionDiabetes MellitusObesityHyperlipidemiaSmokingIranAbout 50 percent of the burden of diseases in low and middleincome countries is attributable to non-communicable diseases (NCD)from which ischemic heart diseases and stroke are among main con-tributors. Hypertension is a leading well-known risk factor for bothconditions [1].Many risk factors have been investigated in association withhypertension as an outcome [2]. However, few prospective studies indeveloping countries have been done to investigate the associationbetween these risk factors and the development of hypertension.The objective of this population-based, prospective study was toinvestigate the association between conventional risk factors and the6-year risk of hypertension in a southern Iranian province, Bushehr.The design and rationale for the Persian Gulf Healthy Heart Project(PGHHP) have been described in detail elsewhere [3].Participants who had a systolic/diastolic blood pressure higherthan or equal to 140/90 mm Hg or took antihypertensive medicine atthe time of interview due to a previous diagnosis of hypertensionwereconsidered hypertensive.The 6-year risk of hypertensionwas calculated as the proportion ofparticipants who had hypertension in the second phase given thatthey were diagnosed as normotensive in the ﬁrst phase.The crude odds ratios were calculated as the cross-product of 2*2contingency tables between the risk of hypertension and the riskfactors. In addition, the associations between the risk of hypertensionand age, sex, education level, smoking, obesity, hyperlipidemia, andDM at the baseline were examined using a multivariable logisticregression model.A total of 3735 participants with a mean age of 40.4 ± 11.7 in theﬁrst phase and 1833 participants (49.1%) with a mean age of 47.2 ±10.6 were included in this analysis. The number and characteristics ofparticipants in the two phases are shown in Table 1.The 6-year risk of hypertension was 16.9% (95% CI 14.9%–19.0%).The association between the risk of hypertension and demographicand conventional risk factors is shown in Table 2. A statisticallysigniﬁcant linear trend for the risk of hypertension was seen as thenumberofmain risk factors (obesity, smoking, hyperlipidemia, andDM)increased (P b 0.001).The 6-year risk of hypertensionwas positively associated with age,overweight and obesity, and hyperlipidemia, but not with sex,education level (except for primary school), smoking, or DM afteradjusting for potential confounding factors.The 6-year hypertension risk was higher in overweight and obeseparticipants than in those with a normal BMI when controlling forpotential confounders. This ﬁnding is consistent with mostly cross-sectional studies carried out in Iran [4] and other parts of the world[5]. However, Juonala et al. reviewed four prospective studies andfound that the risk of hypertension in obese adults who were notobese in childhood was similar to that of non-obese adults [6].Although obesity has been known to be a major cause of hypertensionin many prospective studies, the mechanism for this association isvery complex, and many questions remain to be answered.In the present study, hyperlipidemia was also associated with therisk of hypertension. Hyperlipidemia, both alone and accompanied byhypertension, has been recognized as a risk factor for cardiovasculardiseases, but there is not much evidence indicating that hyperlipide-mia is a risk factor for hypertension. However, the mechanismsthrough which hyperlipidemia affects cardiovascular outcomes andhypertension may be similar.Smoking was not positively associated with the risk of hyperten-sion in the present study. Although smoking has been recognized as apotent risk factor for major advanced cardiovascular events, few largelongitudinal reports are available on the association between smokingand the resulting development of hypertension. Moreover, theliterature on this association is controversial, and at times, evenconﬂicting. Although some studies have shown that smoking is anindependent risk factor for hypertension [7], others have failed toconﬁrm this relationship [8]. In a prospective cohort study in Turkey,Onat et al. reported that smoking plays a protective role in loweringone's hypertension risk. They concluded that smoking plays this roleby modifying the effect of weight on hypertension [2]. Further studiesare needed to unveil the nature and mechanism of the associationbetween smoking and hypertension.DM and hypertension are known to be closely associated, but in thisstudy, diabetic and non-diabetic participants' 6-year risk of hypertensiondid not differ after controlling for potential confounders, particularly forobesity as the most powerful confounder of the relationship. DM andhypertension have been shown to cross-predict each other [9], indicating☆ All authors take responsibility for all aspects of the reliability and freedom from biasof the data presented and their discussed interpretation.⁎ Corresponding author at: The Persian Gulf Tropical Medicine Research Center, No.19, Boostan Alley, Imam St., Bushehr, Iran. Tel.: +98 912 4986083 (mobile).E-mail address: a.ostovar@bpums.ac.ir (A. Ostovar).Table 1Baseline characteristics of participants; the Persian Gulf Healthy Heart study.Phase I Phase IIParticipants (n) Bushehr 2092 1092Deilam 594 351Genaveh 1049 390Total 3735 1833Age (Mean (SD)) 40.4 (11.7) 47.2 (10.6)Sex (M/F) 1752/1983 823/1010Married (%) 85.8 88.7Crude hypertension rate (%) 26.2 29.9620 Letters to the Editorcommon metabolic pathways [10]. However, one explanation for theﬁnding in the present study is the relatively short follow-up period.As shown in Table 2, the coexistence of obesity, DM, andhyperlipidemia was accompanied by an increased risk of hyperten-sion. The highest risk was seen for the simultaneous presence of allthree risk factors. However, smoking is an exception. The presence ofsmoking modiﬁed the effects of other risk factors toward noassociation. As discussed earlier, despite substantive research in thisarea, the mechanisms through which these risk factors affecthypertension and interact with each other remain unclear andcontroversial.Substantial attrition from phase 1 to phase 2 and a relativelyshort study period for investigating long-term effects of some riskfactors such as smoking and DM are two important limitations ofthis study.In summary, this prospective study is a step forward towardunderstanding the risk factors of hypertension in a developingcountry where few prospective studies have been conducted.We are indebted to the staff of the Persian Gulf BiomedicalResearch Institute who gathered information and performed labora-tory tests. This study is a part of The Persian Gulf Healthy Heart Study.References[1] Alwan A, Armstrong T, Bettcher D, et al. Global status report on noncommunicablediseases 2010. World Health Organization; 2010.[2] Onat A, Ugur M, Hergenc G, Can G, Ordu S, Dursunoglu D. Lifestyle and metabolicdeterminants of incident hypertension, with special reference to cigarettesmoking: a longitudinal population-based study. Am J Hypertens Feb2009;22(2):156–62.[3] Nabipour I, Amiri M, Imami SR, et al. The metabolic syndrome and nonfatalischemic heart disease; a population-based study. Int J Cardiol May 162007;118(1):48–53.[4] Janghorbani M, Amini M, Gouya MM, Delavari A, Alikhani S, Mahdavi A.Nationwide survey of prevalence and risk factors of prehypertension andhypertension in Iranian adults. J Hypertens Mar 2008;26(3):419–26.[5] Feng RN, Zhao C, Wang C, et al. BMI is strongly associated with hypertension, andwaist circumference is strongly associated with type 2 diabetes and dyslipidemia,in northern Chinese adults. J Epidemiol 2012;22(4):317–23.[6] Juonala M, Magnussen CG, Berenson GS, et al. Childhood adiposity, adultadiposity, and cardiovascular risk factors. N Engl J Med Nov 172011;365(20):1876–85.[7] Dochi M, Sakata K, Oishi M, Tanaka K, Kobayashi E, Suwazono Y. Smoking as anindependent risk factor for hypertension: a 14-year longitudinal study in maleJapanese workers. Tohoku J Exp Med Jan 2009;217(1):37–43.[8] Narkiewicz K, Kjeldsen SE, Hedner T. Is smoking a causative factor of hyperten-sion? Blood Press 2005;14(2):69–71.[9] Ferrannini E, Cushman WC. Diabetes and hypertension: the bad companions.Lancet Aug 11 2012;380(9841):601–10.[10] Cheung BM, Li C. Diabetes and hypertension: is there a commonmetabolic pathway?Curr Atheroscler Rep Apr 2012;14(2):160–6.0167-5273/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved.http://dx.doi.org/10.1016/j.ijcard.2014.01.080Table 2Association of conventional risk factors and 6-year risk of hypertension, the Persian Gulf Healthy Heart Study, Bushehr.Risk factor Crude OR (CI) Adjusted OR (CI) Adjusted variablesAge (years) 25–34 1 N/A None35–44 2.26 (1.56–3.28) N/A None45–54 3.05 (2.04–4.56) N/A None55–64 3.94 (2.23–6.96) N/A None≥65 5.52 (2.67–18.35) N/A NoneSex (M/F) 1.25 (0.94–1.67) N/A NoneEducation level Academic 1 N/A N/AHigh school 0.67 (0.43–1.03) 0.74 (0.47–1.16) Age, sexGuidance school 0.64 (0.39–1.04) 0.68 (0.41–1.13) Age, sexPrimary school 0.62 (0.39–0.99) 0.49 (0.29–0.83) Age, sexIlliterate 1.77 (1.09–2.87) 1.43 (0.75–2.71) Age, sexObesity1 BMI b 25 1 N/A N/ABMI = 25–29 1.46 (1.03–2.07) 1.51 (1.06–2.16) Age, sex, education levelBMI ≥ 30 1.88 (1.28–2.75) 1.98 (1.31–3.06) Age, sex, education levelSmoking2 1.09 (0.76–1.58) 0.73 (0.49–1.09) Age, sex, education levelDiabetes mellitus3 2.11 (1.37–3.23) 1.34 (0.84–2.13) Age, sex, education level, obesity, hyperlipidemiaHyperlipidemia4 2.07 (1.44–2.98) 1.63 (1.11–2.37) Age, sex, education level, obesity, diabetes mellitusNone 1 N/A N/A1 AND 2 1.80 (1.11–2.91) 1.27 (0.75–2.15) Age, sex, education level1 AND 3 2.85 (1.66–4.89) 2.11 (1.18–3.79) Age, sex, education level1 AND 4 3.00 (1.73–5.22) 2.66 (1.50–4.69) Age, sex, education level2 AND 3 1.45 (0.55–3.80) 0.57 (0.18–1.80) Age, sex, education level2 AND 4 2.13 (1.31–3.47) 1.34 (0.75–2.39) Age, sex, education level3 AND 4 3.71 (2.15–6.43) 2.78 (1.51–5.12) Age, sex, education levelNone 1 N/A N/A1 AND 2 AND 3 1.92 (0.71–5.23) 0.76 (0.22–2.59) Age, sex, education level1 AND 2 AND 4 3.93 (1.28–12.19) 1.20 (0.28–5.11) Age, sex, education level1 AND 3 AND 4 6.00 (2.85–12.63) 4.29 (1.83–10.03) Age, sex, education level2 AND 3 AND 4 2.74 (0.98–7.70) 1.11 (0.30–4.08) Age, sex, education levelNone 1 N/A N/A1 AND 2 AND 3 AND 4 4.76 (1.38–16.68) 2.65 (0.52–13.65) Age, sex, education level621Letters to the Editor

Hypertensionriskandconventionalriskfactorsinaprospectivecohort

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Hypertensionriskandconventionalriskfactorsinaprospectivecohort studyinIran: ThePersianGulfHealthyHeartStudy

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