Jun 18, 1981 - blood pressure appears an effective and critical public health service. However ... weight loss-offers special promise for decreasing blood.
The Experimental Evidence for Weight-Loss Treatment of Essential Hypertension: A Critical Review MELBOURNE F. HOVELL, PHD, MPH
Abstract: The empirical evidence concerning the therapeutic effects of weight loss for hypertension treatment was reviewed. Interventions were critically reviewed for strength of measures and experimental design. Six of 21 intervention studies proved to be methodologically strong. However, only one study was considered a randomized clinical trial, testing the combined effects of weight reduction and pharmacological treatment of hypertension. Average blood pressure decrease obtained from the methodologically
Introduction Blood pressure chronically above 140/90 mmHg predisposes individuals to cardiovascular disease and mortality.1-5 Veterans Administration Hospital Trials and the National Heart, Lung and Blood Institute's Hypertension Detection and Follow-Up Trial (HDFP) indicated that reducing blood pressure (including borderline hypertension) reduces disease and mortality rates.6-12 Thus, vigorous treatment of elevated blood pressure appears an effective and critical public health service. However, "treatment" may consist of components independently or jointly responsible for blood pressure reduction. The HDFP experimental group received stepped-care medication prescriptions in conjunction with counseling to change other risk factors (e.g., smoking, weight), and usualtreatment controls were referred to private physicians.'2 Although both groups were prescribed antihypertensive medication, not all in either group received medication (referred care=54.3 per cent to 70.3 per cent; stepped care=75.4 per cent to 86.3 per cent at five years). The blood pressure, morbidity and mortality differences between groups may have been due to nonpharmacological components of treatment. Investigators have reported therapeutic effects from relaxation, biofeedback, meditation, blood-pressure monitoring, and other nonpharmacologic treatments of hypertension. 13-18 These nonmedication-treatments shed light on possible behavioral factors involved in the etiology, and control of hypertension, and are less dangerous than antihypertenAddress reprint requests to Melbourne F. Hovell, PhD, MPH, Laboratory for the Study of Behavioral Medicine, Department of Psychiatry, Stanford University School of Medicine, Stanford, CA 94304. This paper, submitted to the Journal June 18, 1981, was revised and accepted for publication October 6, 1981.
AJPH April 1982, Vol. 72, No. 4
strongest studies was -21 mmHg and -13 mmHg, for systolic and diastolic measures, respectively. This magnitude change suggests that weight loss may be a clinically and statistically significant treatment. Confounding and bias variables, such as adherence to diet, medication, salt consumption, etc., were discussed and future areas of research were outlined. It was concluded that weight loss appears to be an effective and safe treatment of hypertension. (Am J Public Health 1982; 72:359-368.)
sive medication.19 One nonpharmacological procedureweight loss-offers special promise for decreasing blood pressure.20-22 This paper critically reviews empirical evidence that weight loss decreases blood pressure with special attention to experimentally controlled analyses. This paper does not detail various definitions of hypertension or excess weight, nor are micro level measurements of blood pressure or body weight/composition considered. These are discussed elsewhere.22-28 Prevalence of Hypertension and Overweight Using different standards and measures, researchers have estimated that a large portion of the adult US population is greater than "ideal" weight. The Metropolitan Life Insurance Group has estimated that, for adults over 30 years, 30 per cent of the men and 40 per cent of the women are 20 per cent or more above "desirable" weight.29 The Build and Blood Pressure Study' reported that 6 per cent of males and 11 per cent of females ages 15 to 69 years were 20 per cent or greater than a population standard mean weight for sex and height. Others have reported similar estimates.3033 Prevalence estimates for hypertension (140/90 or greater) range from 10 per cent to more than 30 per cent, depending on age, race and sex.3636 The National Health Survey found about 16 per cent of Whites and 33 of Blacks with blood pressure above 160/95 mmHg, after age adjustment.37 Prevalence of overweight hypertensive persons is most important. Screening of one million people showed 50 per cent higher prevalence of hypertension among selfreported overweight individuals than among those of normal weight.38 Overweight adults were more prevalent among hypertensive persons.3660 In a comprehensive review by Chiang, Perlman, and Epstein,20from 20 per cent to 33 per cent of all hypertensive adults were overweight.
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Association between Blood Pressure and Body Weight Most studies of the relationship of elevated blood pressure to excess weight show that the higher the weight, the higher the blood pressure.61--6 Correlations between weight and blood pressure ranged from .21 to .42 for adults less than 75 years in a number of US studies, and similar findings were reported in Europe.36-38'69,70 An Australian investigation reported correlations of .21 to .35, depending on age and sex, for persons not under treatment for hypertension. For men under 49 years, the relatively high prevalence of systolic hypertension was independent of age after adjusting for weight.66 The authors concluded that weight gain contributed significantly to elevated blood pressure. However, this relationship is not universal. Boyle and coworkers48'64 found the expected positive relation for Whites, but not for Blacks in Charleston, South Carolina. Weisner, et al,6' found small statistically significant correlations (e.g., .18, .19) between weight and blood pressure when controlling for age. The authors concluded that obesity was only a minor determinant of blood pressure. Similarly, Ballantyne and coworkers62 found a positive association only for non-smoker males from an untreated hypertensive population. It also appears that selected societies and social groups which have a narrow range of body weight and/or few persons with high blood pressure show little or no association.39-527' These reports serve to temper conclusions concerning weight and blood pressure. Overall, observational studies argue that excess body weight is related to high blood pressure levels. However, as cross-sectional correlational studies, they do not establish that weight change produces blood pressure change.
Weight Change Association A few longitudinal analyses have reported data showing correspondence between weight change and subsequent blood pressure change.50,72-75 Kannel and associates69 presented information on over 5,000 participants followed for 12 years. Comparing individuals with greatest relative weight gains and those with greatest weight loss showed corresponding increases and decreases in blood pressure, respectively, for obese and nonobese men and women, although statistically significant only for males. For men over 25 years and gaining weight, an increased risk of developing hypertension (160/95 mmHg) was reported. In another Framingham report,72 a 16-year longitudinal assessment was made for weight and blood pressure change. Considering relative weight and weight change by sex and age groups, this study found statistically significant positive regression coefficients between relative weight change and blood pressure change. For each 10 unit change in relative weight, a 6.6 mmHg and 4.5 mmHg change in systolic pressure was observed for men and women, respectively. For each 10 per cent increase in relative weight, there was a 30 per cent increase in incidence of coronary disease for males. For each 10 per. cent decrease in relative weight, there was a 20 per cent decrease in incidence of coronary disease. Slightly smaller relationships were found for women. 360
Another study examined weight change and blood pressure change over six years, where a 10 Kg change in relative weight corresponded to a 3.9 mmHg and 2.7 mmHg change in systolic and diastolic pressures.76 Regression coefficients were roughly .41 and .73 for systolic and diastolic readings. However, in one age stratum, a nonsignificant negative relationship (B=-1.03) was obtained. Thus, this investigation found similar results, but a weaker and less consistent relationship between weight change and blood pressure change, perhaps because the study included only women. These studies provide valuable information concerning weight and blood pressure change. However, they continue to fall short of sufficient information to draw firm conclusionsrabout the effects of weight loss on blood pressure, especially for individuals with hypertension. The proportion of hypertensive persons was not reported and probably small, and, the proportion of persons losing weight tended to be small. In one study,76 each age stratum showed an overall average gain in weight after six years. Finally, these studies did not report the effect, if any, of weight loss on blood pressure for initially hypertensive persons. The relationships observed seem to reflect weight gain and change in normotensive blood pressure. Even if the positive relationship holds for weight loss among hypertensive persons, studies of a "correlational" design cannot rule out possible confounding unmeasured variables. Hypertensive persons may experience various illnesses and medical treatments, which may result in both decreased weight and blood pressure. For such patients it might be erroneous to attribute blood pressure change to weight change. Weight Loss Interventions The best evidence of possible benefits from weight loss must come from experimentally controlled interventions, with hypertensive persons. Only from results of a randomized clinical trial can one be confident that outcomes observed are representative.7 Twenty-one intervention studies were reviewed and rated for measurement and experimental design quality. From these assessments, studies closest to "ideal" were isolated from others as the primary basis for drawing conclusions about weight loss in the treatment of
hypertension.
Methodology Table 1 lists the variables considered in judging the quality of blood pressure measurement and the arbitrary ratings assigned. In clinical research, many samples are limited to persons representing extremes within the population and so may be expected to "regress" toward the mean following initial measures.78 One method of reducing this bias is to use repeated measures. Employing trained personnel (ideally "blind" to the study purpose) strengthens the accuracy and consistency of observations. Thus, repeated measures, trained personnel, and similar measurement variables were examined. Similar standards were employed for weight measures, although rated somewhat differently (Table 2). AJPH April 1982, Vol. 72, No. 4
WEIGHT-LOSS/BLOOD PRESSURE TABLE 1-Blood Pressure Measurement Criteria and Point Ratings Criteria
Points
Repeated measures across calendar time Repeated measures within each visit Explicit observer reliability checks Consistent assessment procedures (e.g., same arm, place, conditions, etc.) Explicitly noted trained personnel Observers experimentally blind to the study purpose and/or group assignment Procedures to reduce expectation bias (e.g., random zero muddler sphygmomanometer)
4 2 3
2 1
3 2
Table 3 shows the standards used to judge the quality of each study's research design. Inclusion of a control group and random allocation were weighted relatively high, while fewer points were assigned for experimenters' being blind to groups or outcomes, adherence measures, and other variables. These ratings reflect only critical measurement and design features. Other procedures may strengthen a study, while idiosyncratic biases may weaken an otherwise strong analysis. Such details are discussed for selected studies.
Results Table 4 depicts overall scores assigned for measurement and design variables, and presence or absence of selected key procedures for each study. Most (67 per cent) of the interventions employed repeated measures of blood pressure and weight. Only two in some way blinded persons recording blood pressure, and only one for weight. No report noted explicit reliability checks for either blood pressure or weight. This is surprising for studies published recently, as blood pressure is subject to considerable variability increasing measurement difficulty78 and even trained observers are subject to measurement errors.100,101 Only four reports for blood pressure and five for weight measures achieved more than half the possible total scores for these ratings. TABLE 2-Body Weight Measurement Criteria and Point Rat-
ings Criteria
Points
Repeated measures across calendar time Explicit reliability checks* Consistent assessment procedures Observers experimentally blind to study purpose and/or group assignments Calculation of relative weight, considering height and sex
4 1 2
3 1
*Only one point, rather than three as for blood pressure, was assigned for explicit reliability checks of weight based on the assumption that weight is more accurately measured than blood pressure.
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TABLE 3-Research Design Criteria and Point Ratings Criteria
Points
Inclusion of control group or condition Random allocation of participants to groups Measurement of controls concurrent in time Equal "treatment" of experimental and control participants, except for the experimental variable under study Consistent procedure (adherence to protocol) Inclusion of adherence masures Inclusion of follow-up assessment Unbiased representative sample from a known population Specification of sample characteristics (e.g., race, sex, age, SES, etc.) Experimenters blind to group assignment and/or measures
4 3 2
2 1 1 1 1 1 2
Only seven reports included comparison groups or other control procedures, and only three included random allocation (Table 5). Most studies were pre-post measures of treatment procedures for clinic patients. Of the seven including "control" groups, one89 controlled only for weight loss and not blood pressure, the major outcome to be controlled. Only four studies earned a score greater than half the possible total score for research design. Nonrandom control procedures are subject to selection bias, where confounding variables (e.g., age, sex, treatment sensitivity) may not be equally distributed among groups. Literature controls suffer from the additional weakness that measures are not obtained at the same time, thus failing to control for the effects of unknown events which occur simultaneously with treatment as explanations for blood pressure change. Linder and Blackburn89 employed a literature control procedure for their weight loss intervention. In behavioral science small sample expefimental designs have been well developed,'02 where an individual or group serves as its own control. Keys and associates88 conducted premeasures, repeated measures during a diet intervention, and finally measures during a partial return toward baseline diet. Weight and blood pressure decreased and increased coincident with intervention and return to baseline, respectively. Master and Oppenheimer described the same sequence for one patient.9' These studies do not provide adequate evidence to warrant generalization to the population at large. However, they do present strong cases for believing that weight loss for their patients was responsible for the blood pressure observed For an adequate test, not only must one group receive treatment while the control does not but, in addition, all other relevant interventions and experiences should be balanced among groups. This is especially difficult with patients reporting to a clinic for "help". Hypertensive patients are no exception. One of the most carefully designed and experimentally controlled studies reviewed93 found nonsignificant differences between groups' changes in blood pressure, probably due to differential adjunctive treatment. Experimental participants received diets for weight loss, while control patients were referred to private physicians. The experimental group lost significantly more weight than the control, and blood pressure decreased in both groups. How361
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TABLE 4-Methodological Ratings Design
Measurement Total Score
Sample Variable Repeat. Meas.
BP
WT
Reference
BP
WT
78 79 80
+
+
-
-
-
-
-
-
-
-
-
-
+
+
-
-
-
-
+ -
-
-
-
+ -
-
+
+ -
-
-
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
-+
+ + + + + + + + +
+
+ + +
+ +
+ + +
Total Score
Control Proc.
(18 poss)
Reliab. Ck.
Observ. Blind
BP
Sample Variable
WT
-
+
+
-
-
-
-
-
-
-
-
-
+
+
-
-
-
-
-
-
-
-
-
ever, only the control group enjoyed an increase in hypotensive prescriptions. Similarly, Tyroler, et al, reported a decrease in hypotensive medications for the experimental group and an increase in prescription for their control
WT
BP (17 poss)
(11 poss)
4 0 0 4 0 9 4 0 10 4 4 4 4 0 10 10 6 5 0 7 1
4 0 0 4 0 7 4 0 7 4 5 4 4 0 8 7 5 5 0 7 1
-
-
+
+
+ + (wt) + + -
+ -
1 0 6 0 0 7 0 0 0 11 6 0 0 0 11 11 0 0 0 13 0
group.98 In this instance, blood pressure differences remained statistically significant for the systolic measure. Failure to adhere to treatment regimens and unequal distribution among experimental groups for participants not
TABLE 5-Summary Results of "Controlled" Studies Random Allocation
Control
Intervention
Reference
Change mm Hg
WT Change kgs
BP Change mm Hg
WT Change kgs
92 93 97
-11.2/-5.3 -6.9/-2.5 -12.0/-8.0
-2.2 -0.7 -1.8
-11.9/-6.9 -37.4/-23.3 -18.0/-13.0
-5.1 -9.5 -8.16
BP
Nonrandom Allocation
83 87 88
0.5/1.3 NA NA
-1.8 NA -10.0
-33.0/-16.0 -5.5/-2.0 -18.2/-14.9
- 15.0
-12.7 -19.5
Overall Crude Mean Change Control
362
Intervention
BP mm Hg
WT kgs.
BP mm Hg
WT kgs.
-7.4/-3.6
-3.3
-20.7/-12.7
-11.7
AJPH April 1982, Vol. 72, No. 4
WEIGHT-LOSS/BLOOD PRESSURE
fully adhering are serious flaws in clinical trials. 10-105 Efforts to assess adherence, as well as sustain it, strengthen intervention studies. The Linder and Blackburn study89 attempted to assess adherence. Blood acetone concentrations from expired air and laboratory physical fitness measures were obtained as indications of diet and exercise compliance. These measures provided only a "some-versus-none" estimate; the degree of adherence was not assessed. It is not clear that such measures were sufficiently sensitive to diet and physical activity behavior. Without validation, it is not known to what degree an individual might adhere to the behavioral prescriptions and fail these tests (false negatives) or vice versa (false positives). The use of these data also raised concern about possible reactivity in this analysis. Patients were threatened with discharge for poor compliance. Such a contingency may have increased dropouts and raises an ethical question for persons receiving treatment. Despite these reservations, this study served as a model for attempting to assess adherence. Can Weight Loss "Cause" Decreased Blood Pressure? Inspection of results reported by the six methodologically strongest analyses84,88,89,93,94,98 provides the best estimate of effects of weight loss on blood pressure. Table 5 illustrates mean weight and blood pressure changes for each study and overall mean changes for all six studies. For the studies using nonrandom allocation, substantial weight loss (-12.7 to -19.5 kgs) was achieved; more modest decreases were observed in controls (-1.8 to -10.0 kgs). Each intervention group concurrently enjoyed mean decreases in blood pressure (-5.5/-2.0 to -331-16 mmHg), but the one control group obtained a small increase in blood pressure (0.5/1.3 mmHg). Weight changes among the studies employing random allocations939498 followed the same pattern, with greatest decreases for intervention groups (-5.1 to -9.5 kgs) and relatively small decreases in control groups (-0.7 to -2.2 kgs). The same trend was observed for blood pressure changes. Intervention groups' blood pressures decreased from -1 1.9/-6.9 to -37.4/-23.3 mmHg, while control's decreased only from -6.9/-2.5 to -12.0/-8.0 mmHg. Collapsing these changes into crude means shows about -21 mmHg systolic and -13 mmHg diastolic change corresponding to about -12 kgs decrease in weight for intervention groups. Similarly, about -7 mmHg systolic and -4 mmHg diastolic blood pressure changes corresponded to approximately -3 kgs of weight in controls. Most studies found statistically significant differences for all or some comparisons. It is interesting that weight loss was achieved by controls and, here too, blood pressure decreased. These results seem to indicate that decreased weight results in decreased blood pressure. However, inspection of individual studies shows some as equivocal. Fletcher" analyzed 155 obese women attending a medical clinic. Of these, 38 had systolic hypertension and 30 had diastolic hypertension. All were prescribed weight reducing diets (600-1000 cal). Analyses were conducted only for women completing four months of treatment, and only for women who lost 6.3 kgs or more compared to those who lost AJPH April 1982, Vol. 72, No. 4
less than 6.3 kgs. Thus, not only were groups not allocated at random, but considerable self-selection probably occurred. This left group equivalence for diet adherence, as well as other variables, questionable. Dropouts were ignored and, if "treatment failures" (those not losing weight or decreasing in blood pressure) were more prevalent among dropouts, results could have been biased, making weight loss seem to lower blood pressure. Defending this analysis, groups had similar age, weight, and initial blood pressures. Moreover, the majority of the dropouts occurred in persons within normal blood pressure categories, which may indicate that obese hypertensive persons are more likely to remain in weight loss treatment than obese normotensive persons. Perhaps all research is removed from the usual or in vivo environment. However, its value depends, in part, on the degree to which analyses are conducted under situations approximating the community at large. The report by Keys, et al,88 may be questioned as an unusual laboratory test. Thirty-two normotensive young men, ages 20-33 years, underwent semistarvation under laboratory conditions. Changes from baseline, starvation diet, and return toward baseline were compared. Not surprisingly, with a mean decrease of 14.95 kgs for normal weight men, other changes including modest decreases in blood pressure were observed. To their credit, the authors reported no serious side effects. Nevertheless, it is unclear to what extent these results relate to weight loss in a "free living" situation or for blood pressure change in overweight hypertensive persons. Their results do point out that weight loss in nonobese persons may reduce blood pressure, raising a question about therapeutic benefits of moderate weight loss in normal weight hypertensive volunteers. No study is perfect, but the analysis reported by Reisen and associates94 comes the closest among the interventions reviewed. One hundred twenty-one obese hypertensive patients participated in two analyses: a pre-post test of weight reduction in patients not receiving hypotensive medications, and random allocation of patients prescribed antihypertensive medication to a weight loss strategy or control group. Control and weight loss plus medication-treatment groups were reported receiving the same medication and dosage. A dietitian regularly interviewed all patients concerning diet and encouraged patients to adhere to their respective treatments. Blood pressure was measured using an automatic machine, thereby reducing observer bias and drift. Repeated measures for each clinic visit yielded individual means provided reasonable estimates of true blood pressures. Weight and blood pressure analyses were adjusted for age, sex, initial levels, and initial per cent overweight. Moreover, the level of sodium excretion was measured for the two diet groups and the medication control. Three relatively modest criticisms for this study are: 1) the 14 dropouts (relatively few) were not included in the analysis; 2) no experimenter blinding procedures were used; and 3) subjects were recruited from a patients population, thereby potentially limiting
generalization. As noted earlier, Reisen, et al,94found decreased weight and blood pressure in the diet only and diet plus medication 363
HOVELL
groups, and relatively little weight loss and decrease in blood pressure for the medicated control group. These differences proved statistically significant, and neither salt consumption nor medication prescriptions appeared to differ among groups. Thus, weight loss, in conjunction with medication treatment, appears to be a more effective means of lowering blood pressure in overweight hypertensive patients than medication alone. Further, the decrease in blood pressure for unmedicated hypertensive patients suggests that weight loss may be an effective treatment alternative to medication.
Collateral Changes Blood pressure changes associated with weight loss may be a function of collateral changes in hypotensive medication consumption. The controlled studies, except for Keys, et al,88 either did not make clear whether participants were prescribed medication84 89 or explicitly noted that the majority were. Both Ramsay, et al,93 and Tyroler, et al,98 noted changes in medication prescriptions. This raises the possibility that weight loss intervention inadvertently results in increases prescriptions and lowered blood pressure. In absence of prescription data, this cannot be ruled out. Not only may prescriptions change, so may the amount of medication consumed, and consumption may increase or decrease. For interventions reviewed, too little information concerning medication adherence was reported to eliminate possible confoundings. The safest conclusion to draw is that weight loss in conjunction with pharmacological treatment seems to lower blood pressure. High salt intake has been associated with increased blood pressure'06 and salt restriction can decrease pressures.'107' 08Dahl and associates'07 suggest that weight loss may have its hypotensive effect via incidental salt restriction with reduced food intake. Studies reviewed do not fully rule out this possibility. However, contrary evidence was reported by Reisen, et al,94 were salt excretion did not change with weight loss. This also was supported in the review by Tobian. '08 Weight loss may be achieved by consuming fewer calories than needed for usual activity levels, by increasing physical activity, or both. These studies concentrated on calorie reduction for weight loss. With the exception of the Linder and Blackburn analysis,89 none reported measuring physical activity. It is possible that changes in physical activity my have accentuated (e.g., increased activity) or compromised the effects of the diet instruction. Changes in physical activity within control groups also could confound results. It seems unlikely that participants in weight loss programs greatly increase their activity level, but this cannot be ruled out. Future studies could provide valuable information by measuring and/or controlling activity levels. Incidental salt reduction with calorie restriction may be the mechanism of blood pressure control, as noted earlier. However, there may be other ways by which salt or other factors confound the possible effects of weight loss on blood pressure. Noppa76 reported that only about 1 per cent to 18 per cent of the blood pressure variance was determined by weight change, depending on age. Tyroler, et al,98 noted that only a small part of the blood pressure decrease seemed 364
attributable to weight loss. They suggested that psychotherapeutic benefits of treatment contributed to the hypotensive results. Given decreased blood pressure simply from monitoring,'4"'0 relaxation, and biofeedback procedures,16 it seems possible that weight loss intervention has effects for reasons over and above weight decreases. Perhaps social interaction between caretaker and patient has a direct effect on physiology,"' reducing "stress" and blood pressure. Future research should explore the effects of usual components of weight loss treatments. Although adherence to medication is a recognized concern,'09 it seems implausible that the blood pressure changes reported in studies reviewed were a function of collateral increases in medication; increased adherence does not appear to limit the practical value attributable to weight loss. However, the limited evidence showing blood pressure decrease with weight loss, in absence of salt restriction, is insufficient to determine separate effects of these variables. If lowered blood pressure is due to salt reduction, then patients may be subjected to possible emotional and financial expense from weight loss treatment, when simple salt restriction might be as effective. Additional studies are needed to tease out the separate and combined effects of weight and salt reduction. Replication and Generalization Replication determines reliability of an association. The generalizability of an association is demonstrated by replication under varying circumstances. Most of the 21 intervention studies reviewed showed a positive association between weight loss and blood pressure decrease. Table 6 reveals that these reports were distributed across four different age groups in both males and females. Although foreign research was not systematically sampled, this survey shows positive results in England, Israel and the US. These replications, uncontrolled and controlled, present a compelling argument for the generalization that weight loss reduces blood pressure. Failure to conduct analyses by socioeconomic status and the questionable function of weight change among Blacks tempers this conclusion.
Potential Therapeutic Value of Weight Loss Estimated Incidence Reduction Tyroler and associates98 presented an enticing analysis of the seven-year incidence of diastolic hypertension and relative risk for weight change. Across initial weight groups, they obtained an incidence for diastolic hypertension of 16.8 per cent. Over half (58.3 per cent) of individuals gaining more than 4.5 kgs and initially overweight, were hypertensive (diastolic). Comparing the incidence of overweight persons who gained 4.5 kgs or more with normal weight persons who gained less than 4.5 kgs (including persons losing weight), the relative risk of diastolic blood pressures above 105 mmHg was 6.9. Comparing various initial weight and weight change groups showed relative risks of diastolic hypertension almost universally above 1.5. Thus, many AJPH April 1982, Vol. 72, No. 4
WEIGHT-LOSS/BLOOD PRESSURE TABLE 6-Distribution of Weight and Blood Pressure Outcomes by Age, Sex and Country Wt. Decrease
NR*
Total
Systolic Decrease
NR
Total
Diastolic Decrease
NR
Total
N= 18
3
21
N= 16
5
21
N= 15
6
21
Age (years)
20-30 31-40 41-50 51+ NR Sex M&F M F NR Country United States England Israel NR
3 4 6 3 2
3 4 6 2 1
2 4 6 2 1
11 3 3 1
8 3 4 1
3 4 1
14 3 1 0
11 4 1 0
10 4 1 0
7
*Some studies did not report (NR) weight change, blood pressure change, or the age or sex of participants.
people were becoming hypertensive, especially among weight gainers initially overweight. Assuming a causal relationship, these investigators estimated that a 41 per cent reduction in the incidence of diastolic hypertension could be achieved, providing at least one-third of their cohort received treatment, that treatment decreased weight in those initially overweight and prevented weight gain in those of normal weight. Two tentative conclusions might be drawn from these estimates: 1) almost half of expected hypertension cases may be prevented by weight loss and prevention of weight gain in normotensive persons; and 2) enormous effort and community resources are necessary to reduce weight gain in one-third of the adult population. Tyroler and associates" offer a tantilizing possibility and challenge. Expectations for Effective Weight Loss Intervention Within the weight loss literature, behavior modification is held as an effective weight loss intervention. 112,113 However, as noted by Wooley and associates,"4 these treatments offer no panacea. The degree of weight loss is about 4.5 to 6.8 kgs, with relatively poor maintenance beyond one year for behavioral treatments. Indeed Graham and coworkers"5 showed only a modest mean weight loss (3.32 kgs) 4.5 years after treatment. However, the weight changes reported for the 21 studies reviewed here hint at greater effectiveness among hypertensive patients (crude mean weight loss of 12.5 kgs). Perhaps overweight hypertensive persons are more responsive to weight loss treatment than are normotensive overweight, as suggested by the fewer dropouts among hypertensive patients reported by Fletcher.84 Reported weight loss of 4.5 kgs to 13.5 kgs justifies hope of achieving moderate weight loss. It should be noted that mean weight losses of 4.5 kgs approaches the more "effective" level reported by Tyroler and associates98 for which estimates of decreased risk of hypertension were made. AJPH April 1982, Vol. 72, No. 4
Future Research This review suggests a number of areas for further investigation. A randomized clinical trial of the effects of weight loss in overweight borderline hypertensive patients not taking hypotensive medication is needed to separate the effects of weight loss alone from weight loss plus medication. A controlled trial testing weight loss while salt consumption is held constant and analysis of salt reduction without weight loss in obese hypertensives could provide data illuminating the various diet treatment options. Based on Keys, et al,88 and other studies reviewed, where weight loss in nonobese persons resulted in blood pressure decreases, it may be useful to test the value of moderate weight reduction in normal weight hypertensive volunteers, especially those with borderline hypertension. Component analyses of weight loss intervention may be valuable as well. Such studies may be able to identify "caring" procedures and/or sensitizing effects which could aid nonobese hypertensives or obese hypertensives unable to lose weight. A tantilizing hypothesis, worthy of experimental test, concerns the possible behavioral-psychological differences for weight loss among hypertensive versus normotensive overweight persons. Obese hypertensive patients, concerned about high blood pressure, may be more "motivated" to follow weight loss instructions than the overweight, normotensive patients. The interventions reviewed provided no information concerning long-term efforts of weight loss intervention. Weight loss tends to be fragile, with limited maintenance. The long-term success of weight loss among hypertensive persons and the permanence of blood pressure reduction is another area of needed research. In conjunction with maintenance analyses, assessment of changes in morbidity and mortality would provide important estimates of the ultimate health benefits. Providing weight loss can be maintained, a 365
HOVELL
large scale community trail, including morbidity and mortality measures, may be appropriate. Finally, a primary prevention test of weight loss/maintenance, in persons at risk for development of hypertension, seems warranted.
Conclusions The National High Blood Pressure Education Program Coordinating Committee'"6 published formal recommendations concerning the dietary management of hypertension: ". ... For borderline hypertension in subjects with weight, or in those overweight subjects with drug intolerance, weight reduction has been suggested as a reasonable first step in treatment, with careful monitoring of progress by the patient's physician . . ." excess
This review of uncontrolled and controlled treatment studies supports the Committee's recommendations, with the best evidence provided by one methodologically well designed study.94 For practical purposes, weight loss appears an effective adjunctive therapy when combined with pharmacological treatment to reduce blood pressure in overweight hypertensive patients, and may offer similar benefits to nonmedicated patients.
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ACKNOWLEDGMENTS This paper was prepared while the author was serving as a postdoctoral scholar in epidemiology, School of Public Health, University of California, Berkeley. The advice and editorial assistance of L. Syme, B. Cann, F. Hovell, C. Cauchi, W. Winkelstein, W. Reeves and coworkers at Stanford are acknowledged and appreciated. Preparation of this manuscript was supported, in part, by grants (Behavioral Factors in Cardiovascular Disease Etiology No. HL7365, University of California, Berkeley; and Recruitment and Adherence contract No. 71-2161-L) from the National Heart, Lung, and Blood Institute, DHHS.
Study Tour on Water Pollution Control
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A study tour on the control of water pollution in the management of water resources in the United Kingdom will be held September 5-19, 1982 under sponsorship of the United Kingdom Committee of the International Association on Water Pollution Research. Stopovers include London, Cambridge (Stevenage), York, Edinburgh, Windermere, Chester, and Bristol. Research centers, water and wastewater treatment plants, and water resource facilities will be visited. Accompanying persons are welcome. Contact: D. H. Newsome, Department of the Environment, Water Data Unit, Reading Bridge House, Reading RG1 8PA, UK. Since the number of places on the Study Tour is strictly limited, early registration is strongly advised. 368
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