Community Education for Cardiovascular Disease Prevention

Transcription

1 American Journal of Epidemiology Copyright O 996 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved Vol. 44, No. 4 Printed in U.S. A Community Education for Cardiovascular Disease Prevention Morbidity and Mortality Results from the Minnesota Heart Health Program Russell V. Luepker, Lennart Rastam, ' 2 Peter J. Hannan, David M. Murray, Clifton Gray, William L Baker, Richard Crow, David R. Jacobs, Jr., Phyllis L Pirie, Steven R. Mascioli, ' 3 Maurice B. Mittelmark, ' 4 and Henry Blackburn The Minnesota Heart Health Program was a community trial of cardiovascular disease prevention methods that was conducted from 980 to 990 in three Upper Midwestern communities with three matched comparison communities. A 5- to 6-year intervention program used community-wide and individual health education in an attempt to decrease population risk. A major hypothesis was that the incidence of validated fatal and nonfatal coronary heart disease and stroke in 30- to 4-year-old men and women would decline differentially in the education communities after the health promotion program was introduced. This hypothesis was investigated using mixed-model regression. The intervention effect was modeled as a series of annual departures from a linear secular trend after a 2-year lag from the start of the intervention program. In the education communities, 2,394 cases of coronary heart disease and 8 cases of stroke occurred, with 2,526 and 39 cases, respectively, being seen in the comparison communities. The overall decline in coronary heart disease incidence was.8 percent per year in men (p = 0.03) and 3.6 percent per year in women (p = 0.00). For stroke, there were no significant secular trends. The authors recently published findings showing minimal effects of sustained intervention on risk factor levels. In the current report, there was no evidence of a significant intervention effect on morbidity or mortality, either for coronary heart disease or for stroke. Am J Epidemiol 996;44: cardiovascular diseases; health education; health promotion; morbidity; mortality; primary prevention Atherosclerosis, clinically manifest as coronary heart disease and stroke, is the major cause of death and disability in many Western industrialized societies (, 2). Strong downward trends in heart disease mortality rates have been observed since the late 960s, and even longer for stroke (3,4). The improvements in heart disease mortality are associated with declining population levels of serum cholesterol, blood pressure, and cigarette smoking (5, 6), while for stroke, they are associated with declining blood pressure levels, achieved partly through better detection and treatment of hypertension (). Received for publication August 8, 995, and in final form January 2, 996. Abbreviations: MHHP, Minnesota Heart Health Program; ICD-9, International Classification of Diseases, Ninth Revision. Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis, MN. 2 Current address: Department of Community Medicine, School of Medicine, Lund University, Malmd, Sweden. 3 Current address: American Medical Systems, Minnetonka, MN. 4 Current address: Department of Psychosocial Sciences, School of Psychology, University of Bergen, Bergen, Norway. Reprint requests to Dr. Russell V. Luepker, Division of Epidemiology, School of Public Health, University of Minnesota, 300 South Second Street, Suite 300, Minneapolis, MN A number of community trials designed to enhance these salutary disease trends have been implemented in the United States and Europe, beginning in the early 90s (8-5). Their purpose has been to develop and test interventions designed to decrease the public health burden of cardiovascular disease. A common denominator has been the use of community-wide and individual health education to influence levels of risk factors, mainly by improving eating and activity patterns and reducing smoking. All of these projects have reported mixed results with regard to risk factor changes (8-0, 6-; C. Smith, Health Promotion Wales, personal communication, 994), with more favorable outcomes being seen in the earlier studies (8-0, 6). Only the North Karelia Project has published results for morbidity and mortality (, ) during 0 years of follow-up, reporting a favorable effect of intervention on ischemic heart disease mortality (). The Minnesota Heart Health Program (MHHP) was the largest of the studies completed, and it involved six communities in Minnesota, North Dakota, and South Dakota (2). The MHHP results regarding changes in risk factor levels were recently published (); the 35

2 352 Luepker et al. changes were modest and usually within levels attributable to chance. The present paper is the final report on the main outcomes of the MHHP. It presents the results of the intervention program on morbidity and mortality from coronary heart disease and stroke in intervention communities relative to trends observed in the comparison communities. MATERIALS AND METHODS The Minnesota Heart Health Program The MHHP was a research and demonstration project conducted during the 980s ( ) and intended for primary prevention of coronary heart disease and stroke. The intervention program involved three communities in Minnesota and North Dakota with a total of approximately 0,000 inhabitants (2, ). It operated on both the individual level and the community level and was based on several theories of behavior change (-28). It developed and implemented a number of community-wide intervention approaches, including mass media campaigns (), systematic risk factor screening and education (30), changes in the environment to encourage "hearthealthy" behavior (3), and direct education of young people (), adults, and health professionals (33). The program aimed specifically at lowering population levels of blood cholesterol, blood pressure, and smoking and increasing the level of physical activity. Research design The research design of the MHHP has been described in detail elsewhere (). Briefly, the MHHP was a nonrandomized community trial with three community pairs (table ). For each pair, two communities were selected that were similar in terms of size, structure, and distance from Minneapolis. Within each pair, one community was chosen, not randomized, for intervention and the other for comparison. As figure shows, the intervention program began on November, 98, in, Minnesota. Twenty-two and 28 months later, respectively, it began in Fargo- Moorhead (North Dakota-Minnesota) and in, Minnesota. The program continued for 5-6 years in each community, with a transition of program coordination to local advisory boards toward the end of that period. Study endpoints Population-wide data on first events of definite coronary heart disease and stroke were used for this study, with restriction to men and women aged 30-4 years and resident in one of the six communities at the time of their event. Hospital discharge register codes (International Classification of Diseases, Ninth Revision (ICD-9) (35)) from 39 hospitals in the six communities (one small hospital declined participation) were used to identify candidate events. The candidate events were then validated with medical records by a standard protocol, summarized below. For out-of-hospital coronary heart disease, candidate events were identified from computerized mortality tapes obtained from the three state Departments of Health and then validated. Out-of-hospital stroke deaths, a small fraction of cases in the age group 30-4 years, were not systematically sought and thus were not included in the analyses. As figure shows, surveillance started in 980 or 98 in all cities and continued for 9 years in and, Minnesota; for 0 years in Fargo- Moorhead and in, South Dakota; and for years in and, Minnesota. TABLE. Characteristics of the paired Intervention and comparison communities in the Minnesota Heart Health Program, Characteristic and community pair* Small rural Large rural Fargo/Moorhead Metropolitan suburban Total populatlont 3,809,053 04,63 8,484 8,95 4,83 Population aged 30-4 yaarsf 3,5 9,53 3,35,054 38,948,5 * All communities are located in Minnesota, except Fargo (North Dakota) and (South Dakota), t 980 US Census data. Validation of definite coronary heart disease The diagnosis of definite coronary heart disease included both fatal and nonfatal cases and both inhospital and out-of-hospital events. It comprised four distinct categories: ) definite in-hospital myocardial infarction (fatal or nonfatal); 2) definite out-ofhospital myocardial infarction; 3) sudden cardiac death; and 4) definite fatal out-of-hospital coronary heart disease. Thus, all nonfatal cases were hospital admissions. Definite in-hospital myocardial infarction. The first category was based on abstraction of records for casepatients residing in one of the MHHP communities and discharged alive or dead from one of the participating hospitals with any of the ICD-9 codes or Events were validated on the basis of a

3 Community Education for Cardiovascular Disease Prevention Project Year Calendar Year (Education) Education Program (Comparison) Surveillance(Both Towns) Fargo-Moorhead (Education) J Education Program (Comparison) Surveillance(Both Towns) (Education) Education Program (Comparison) SurveillancefBoth Towns) " Surveillance Data Includ^n Analysis ^ 3 Surveillance Data Excluded From Analysis H ^ " n ( e n s e Educa^ : : i Transittona, Period i : : g l^j H ] C o m m u n i t y Ownership ' ' FIGURE. Outline of the 2-month periods defining the baseline and education years in the Minnesota Heart Health Program communities, E-3, E-2, E-, and E0 are the baseline years, and E-E6 are the education years. Hatched areas Indicate periods with data collection and event validation that was used for definition of first events but not for the final analyses. standard approach to data on enzyme patterns and electrocardiographic recordings obtained from the medical records. The records were abstracted by trained nurse abstractors under the supervision of a physician. A prerequisite for validation as definite myocardial infarction was the availability of data on the enzymes creatinine phosphokinase or creatinine phosphokinase-myocardial band. In the absence of enzymes or the presence of a normal enzyme pattern, the case could not be classified as definite. Table 2 shows the algorithm for classification of an enzyme pattern as abnormal or equivocal for the two enzyme measures. All events with abnormal enzyme patterns were classified as definite. With an equivocal enzyme pattern, the case was classified as definite when electrocardiograms showed "evolving evidence" of myocardial infarction: a minimum of two recorded electrocardiograms with an evolving Q-wave pattern, or ST-segment depression or elevation or T-wave inversion, in the setting of equivocal Q waves. This method, which uses a special Minnesota electrocardiographic code (36), is described in detail elsewhere (3). Out-of-hospital myocardial infarction. The second TABLE 2. Algorithm used for classification of enzyme patterns in coronary heart disease cases for which data were abstracted from medical records for validation, Minnesota Heart Health Survey, CPK-MB* data missing CPK-MB <00%f or negative CPK-MB 00-99% or positive CPK-MB 0% CPK'data missing CPK <0O%t CPK 00-99% CPK io% Normal Equivocal Normal Normal Equivocal Equivocal Equivocal Equivocal * CPK, creatinine phosphokinase; CPK-MB, creatinine phosphokinase-myocardial band. t Percentage of the reference value at each hospital. Negative/positive refers to cases in which the actual CPK-MB value was not provided. Am J Epidemiol Vol. 44, No. 4, 996

4 354 Luepker et al. category comprised only fatal cases and was based on computerized information from the mortality registers of the three state health departments. Cases were abstracted for residents in the MHHP communities aged 30-4 years with ICD-9-code(s) 40-44, 42.5, 428, or given as the underlying cause of death on the death certificate. The diagnosis was regarded as definite either when myocardial infarction was verified by autopsy records or when informant interviews, performed 2-4 years after the death, gave evidence of hospitalization due to acute myocardial infarction during the 4 weeks before death. These interviews were performed via telephone by trained interviewers according to a strict protocol. Sudden cardiac death. The third category was also based on computerized information from the death registers. All records on age-eligible MHHP resident cases with ICD-9-code(s) 40-44, 42.5, 428, or given as the underlying cause of death were abstracted. The diagnosis was regarded as valid when the informant interview indicated that death had occurred within hour of acute cardiac symptoms or within hour of the last observation with no symptoms. Definite fatal out-of-hospital coronary heart disease. The fourth category included age-eligible MHHP resident fatal cases occurring out-of-hospital, with ICD-9 code(s) given as the underlying cause of death and an informant interview or autopsy indicating a history of myocardial infarction or severe coronary artery disease or death within - hours after the onset of symptoms. Validation of definite acute stroke For stroke, patients residing in one of the MHHP communities who were discharged from any of the participating hospitals (alive or dead) with any of the ICD-9 codes 40, 4, 430-4, 4, 436, or 43 were selected, and data were validated using information abstracted from the medical records. A case was excluded when physician findings, computerized tomography, or autopsy gave evidence of brain tumor or metastasis, epidural or subdural hematoma, subarachnoid hemorrhage, systemic embolism, or a comatose state of any other origin (e.g., hepatic, diabetic, hypoglycemic, uremic, or epileptic). Following these exclusions, a case was labeled "definite" if an autopsy demonstrated evidence of cerebral infarction or cerebral hemorrhage. When an autopsy was not performed, all three of the following criteria were required: ) a localizing neurologic deficit and/or a change in the patient's state of consciousness, with a history of rapid onset (less than 48 hours from onset to time of admission or to maximum acute neurologic deficit or death); 2) documentation of the localizing neurologic deficit by unequivocal physical or laboratory findings (computerized tomography showing evidence of either cerebral hemorrhage or cerebral infarction) within 6 weeks of the onset of symptoms; and 3) more than hours' duration of unequivocal physical findings, or findings leading to death, or death within hours after onset of symptoms. Definition of fatality Irrespective of whether a hospitalized patient was discharged ah've or dead, an event was defined as fatal if death occurred within 28 days of admission to hospital. This classification was obtained by record linkage between the MHHP case register and the state health department mortality registers. Elimination of repeat events The present study included the first event in the study period for each subject. In the case of multiple events, definite in-hospital myocardial infarction took priority over definite out-of-hospital coronary heart disease or sudden cardiac death. If, in one subject, there remained more than one in-hospital myocardial infarction, the first of those events was selected. However, one subject could contribute to both the register of definite coronary heart disease and the register of definite stroke on separate occasions for example, by having a definite stroke followed by a fatal definite coronary heart disease event. Assignment of events to baseline and education years Each validated event was assigned to a specific 2-month period based on the date of hospital admission for hospitalized cases and the date of death for nonhospitalized cases. For each pair of communities, the annual start of a new year was defined as the month in which the intervention program began in the intervention community of the pair (figure ). This gave one complete baseline year (E0) and one incomplete baseline year (0 months during E-l) in and. In Fargo-Moorhead and Sioux Falls, there were three complete baseline years (E-2, E-l, and E0) and one incomplete baseline year (8 months during E-3). Events that occurred during all of these months were used in the analyses, together with those of the four complete baseline years in and. However, the first 2 months of 980 in and were not included in the analysis.

5 Community Education for Cardiovascular Disease Prevention 355 For education years, only those years having complete data from all six communities were used. Therefore, events that occurred after November, 98, in and ; after September, 989, in Fargo-Moorhead and ; and after March, 990, in and were not used. This left six complete education years for each community pair (E-E6). Thus, E-3, E-2, E-l, and E0 were the consecutive 2-month periods before intervention began, and E-E6 were the 2-month periods of intervention. Statistical methods Rates specific to sex, community intervention, year, and 5-year age stratum were calculated as events per person-year of exposure. Population sizes in each community were taken from the US Censuses for 980 and 990, by sex and 5-year age group. Person-years of exposure by sex, age group, and community were estimated by linear interpolation of the census figures, allowing for the time offsets between baseline/education year and calendar year. Rates were standardized to the 985 age structure of all MHHP communities. Weights were assigned to each rate, reflecting the number of person-years involved. The analysis method was the same as that used with MHHP cross-sectional risk factors, and it is described in detail elsewhere (38). The mixed-model regression analysis was carried out using the MIXED procedure of the Statistical Analysis System (SAS Institute, Inc., Cary, North Carolina; version 6.09). The unit of analysis was the city-year mean, each weighted by personyears of exposure. Year and the MHHP intervention were treated as fixed effects, and community was treated as a nested random effect. A common linear secular trend was estimated from all years (including E-3 and E-2) in comparison communities and from years prior to E3 in the education communities. The MHHP intervention was represented by a series of year-specific departures from that secular trend, beginning in E3, to allow for an a priori 2-year lag postulated between any risk factor effect and an impact on morbidity and mortality. Men and women were analyzed separately. and had no data for the years E-3 and E-2. This was not a problem in the mixed-model regression analysis, but it prevented calculation of pooled education and comparison mean rates for those years without assumptions about the missing rates. For presentation of those pooled rates, shown in the lefthand panels of figures 2 and 3, we avoided assumptions and calculated weighted mean rates for only the years E-l through E6; however, to aid interpretation, we shifted the rate in each community in each year by a constant community-specific amount to equalize the weighted mean rates in the education and comparison conditions in years E-l through E2. RESULTS Coronary heart disease A total of 4,9 cases of definite coronary heart disease occurred during follow-up, 3,66 (4.4 percent) in men and,9 (.6 percent) in women. As table 3 shows, the proportion of fatal cases did not differ between men (3.9 percent) and women (36.9 percent) (p = 0.6). Among fatal events, the most striking sex difference was a higher proportion of sudden cardiac death in men (3. percent; 54/,386) than in women (.4 percent; 09/465) (p < 0.000). Of the total number of cases, 2,394 (48. percent) occurred in the education communities and 2,526 (5.3 percent) in the comparison communities. Within each community, there was large year-to-year variation in the number of events (Appendix table ). This variability is reflected in the community-, year-, and sex-specific age-adjusted yearly event rates presented in table 4. For the years when data from all communities were available, adjusted event rates for the pooled education and comparison communities are presented in the left-hand panel of figure 2. In these aggregated data, there was also large variation, but striking symmetry was seen between the two sets of communities, especially for men. Application of the mixed-model regression analysis confirmed a downward linear trend in the event rate for both men and women. The event rate for coronary heart disease decreased by.8 percent per year for men (p for slope = 0.03) and 3.6 percent per year for women {p for slope = 0.00); these secular trends are TABLE 3. Distribution of the subclasses of definite coronary heart disease and stroke among men and women, Minnesota Heart Health Survey, No. Men No. Women Nonfatal acute myocardia) infarction 2, Fatal acute myocarcfial infarction, In-hospital fatal acute myocardal infarction Out-of-hospital acute myocardal infarction Sudden candfiac death Definite fatal coronary heart disease All definite coronary heart dsease 3, , All definite stroke (in-hospital only)

6 356 Luepker et al. TABLE 4. Age-standardized rates (per 00,000 person-years]) of definite coronary heart disease (fatal and nonfatal combined) in men and women aged 30-4 years when the event occurred, Mnnesota Heart Health Program, * Education year Community E-3 E-2 E- EO E E2 E3 E4 E5 E6 Men Fargo-Moo rhead Woman Fargo-Moo rhead * The standard population was the total population aged 30-4 years in the six study communities plotted in the right-hand panel of figure 2. Also shown in figure 2 are the annual deviations from the trend observed in the three education communities, along with 95 percent confidence intervals; all of these confidence intervals overlapped the fitted secular trend, and none of the annual deviations were statistically significant. Fitted linear trends for the education communities during years E3-E6, forced through the origin at E2 (the latest point prior to the hypothesized intervention effect), had slopes that were not different from those of the unconstrained secular trends among men and women. An age-stratified analysis showed similar results, with no significant MHHP effects for ages above and below 65 years. The same was true for a subgroup analysis restricted to fatal cases. Stroke A total of,55 patients had a definite stroke; 90 strokes (58.3 percent) occurred in men and 650 (4. percent) in women (table 3). Of the total number, 8 (52.5 percent) strokes occurred in the education communities and 39 (4.5 percent) in the comparison communities. Just as for coronary heart disease, there was considerable variation between the annual numbers of events (Appendix table 2). This variability was again reflected in the community-, year-, and sex-specific age-adjusted yearly event rates presented in table 5. For the years when data from all cities were available, adjusted event rates for the intervention and comparison areas are presented in the left-hand panel of figure 3. The mixed-model regression analysis revealed no significant linear secular trends for stroke. In men, the mean annual change was a decline of 0.5 percent per year relative to the level at El (p for slope = 0.8), and in women there was an increase of 2.3 percent per year (p for slope = 0.36). Also shown in figure 3 are the annual deviations from the trend for the intervention communities, with 95 percent confidence intervals. As for coronary heart disease, all confidence intervals for stroke overlapped the fitted trend, and none of the annual deviations were statistically significant. The fitted linear trend for stroke in years E3-E6, forced through the origin at E2, did not deviate significantly from the secular trend. None of the above results changed with stratification by age. DISCUSSION This paper reports the final results of one of the most complex community trials yet conducted in cardiovascular disease prevention. To our knowledge, it is the first to provide controlled data on the possible impact of a community-wide intervention on fatal and nonfatal cardiovascular disease rates. The results are clear: There was no evidence of a significant intervention effect on morbidity or mortality, either for coronary heart disease or for stroke. This is not surprising, given the recently published risk factor findings from the MHHP () and given the strong and favorable secular trends in coronary heart disease risk with which the intervention program had to compete. We recently reported that the MHHP had only modest effects on population risk factor levels (). That report also documented the strong, 2-3 percent annual decline in a coronary heart disease risk

7 Community Education for Cardiovascular Disease Prevention 35 POOLED AND AGE-STANDARDIZED EVENT RATES FITTED SECULAR TREND AND MHHP EFFECT ESTIMATES 500" Male* " c^- 400" T ~~~ - =LJ EDUCATION YEAR o- i r EDUCATION YEAR EDUCATION COMMUNTTES COMPARISON COMMUNmES - EDUCATION EFFECT, I 95% CONFIDENCE BOUNDS SECULAR TREND FIGURE 2. Effect of a community education program on definite coronary heart disease rates among 30- to 4-year-old men and women in the Minnesota Heart Health Program (MHHP), All results are standardized to the mean population of subjects aged 30-4 years in the study communities. Left panel: Age-standardized event rates, pooled between communities using numbers of personyears In each community as weights. The rates were adjusted to provide a common mean level between educated and comparison communities during baseline and lag periods (E- through E2). Right panel: Fitted secular trend and annual MHHP effect estimates; bars, 95% confidence intervals. score for comparison communities (39, 40) during the MHHP intervention period. In the MHHP, the annual decline in coronary heart disease event rates in comparison communities was.8 percent in men and 3.6 percent in women. Both slopes were statistically significant. This corresponds to an accumulated decrease during the 4 years of observation (E2-E6) of.2 percent in men and 4.4 percent in women. It now seems unlikely that a project using local methods of public education would be able to augment this significant background trend over such a short period. Such trends were not anticipated when the MHHP was designed in the late 90s. In contrast, secular trends in stroke were less striking. While stroke mortality continued to decline nationally during the 980s, it plateaued in the Minnesota Heart Survey communities (Minneapolis-St. Paul) from 980 to 990 (). National data on stroke morbidity during the same interval are lacking, but the Minneapolis-St. Paul age-adjusted in-hospital event rate for stroke declined from 980 to 985, from,03 to 988 per 00,000 male inhabitants and from 926 to 804 in women (). Simultaneously, the proportion of in-hospital definite stroke (validated as in the MHHP) increased from 43 percent to 50 percent in men and from 4 percent to 5 percent in women (). Together, the Minnesota Heart Survey data indicate no trend in the definite stroke rate in men and an increase of about 2.5 percent per year in women. The pattern corresponds well with the observations of the MHHP. One possible reason for this break in the continuous decline in stroke incidence is ascertainment bias due to increasing use of computerized tomography (). Therefore, it is possible that the MHHP intervention was competing with downward population trends in stroke incidence as well. The fact that the MHHP was unable to demonstrate improved prevention of first stroke was also expected in view of the intervention's limited impact on average blood pressure levels in the education communities relative to the reference communities notably on the

8 358 Luepker et al. TABLE 5. Age-standardized rates (per 00,000 person-years) of definite in-hospital stroke (fatal and nonfatal combined) In men and women aged 30-4 years when the event occurred, Minnesota Heart Health Program, * Education year Community E-3 E-2 E- E0 E E2 E3 E4 E5 E6 Men Fargo-Moorhead Women Fargo-Moorhead * The standard population was the total population aged 30-4 years in the six study communities prevalence of treatment for hypertension and on blood pressure levels in treated patients (, 4). The North Karelia Project published morbidity data for the first 5 years of intervention (), but the design was not controlled, and in view of the strong secular trends in Finland, the findings are not conclusive of an intervention effect. The Finnish investigators have continued to compare coronary heart disease mortality rates in North Karelia with those in the reference community and in all of Finland. They demonstrated more rapidly declining rates during the first years in the intervention community than in these reference populations (). The North Karelia Project may have achieved some acceleration of a strong secular trend, but whether this should be attributed to the intervention program has been questioned (42). There were also fundamental differences in the circumstances in which the North Karelia Project and the MHHP were conducted. The Finnish project was instituted in 92 in a part of Europe that had some of the highest coronary heart disease rates in the world, with the levels of related risk factors being extremely high. The MHHP, on the other hand, involved populations at or below the average risk of populations in other industrialized countries. Thus, while there were downward secular trends in both areas, the rates moved from extremely high to high in North Karelia while staying within the medium range in Minnesota. The MHHP was started 0-2 years later than the Finnish study, when interest in coronary heart disease prevention in clinical medicine and the mass media was already high. In the United States, the National High Blood Pressure Education Program (43) was well along, and the National Cholesterol Education Campaign (44) had begun. For many years, Minnesota also had an integrated program of legislation regarding the control of smoking in public areas. Thus, Minnesota was already in an accelerated phase of risk reduction when the MHHP began. These differences may well be the most important reasons for the difference in outcome from the Finnish project. Neither the North Karelia Project nor the MHHP appeared to have any impact on stroke rates. This may be a consequence of the relatively lesser emphasis placed on a high-risk approach. An aggressive program for identification and treatment of hypertension can influence the incidence of stroke in the population, as was recently demonstrated in a Swedish trial (45). Other community trials have reported effects on risk factor levels. Favorable results were described by the Stanford Five-City Project (8) and the German Cardiovascular Prevention Study (4), while the Pawtucket Heart Health Program (2) and the Heartbeat Wales Programme (C. Smith, Health Promotion Wales, personal communication, 994) had ambiguous results similar to those of the MHHP. The cardiovascular event rates of these studies have not yet been reported at diis writing. Methodological considerations Several methodological issues warrant further consideration. First, hospital morbidity data and death certificate data became available annually, and this created a mismatch between those data and the MHHP education schedule, leaving incomplete years at the end of the MHHP (figure ). We considered using the rates from all partial years, weighting by person-years of exposure. However, in the presence of a measurable trend, this procedure would lead to bias in the full-year

9 Community Education for Cardiovascular Disease Prevention 359 POOLED AND AGE-STANDARDIZED EVENT RATES FITTED SECULAR TREND AND MHHP EFFECT ESTIMATES y - / 00- Mate 80-60" 40- Females T~ < -^ " EDUCATION YEAR o- I EDUCATION YEAR EDUCATION COUHUNTTES COMPARISON COMMUNITIES I EDUCATION EFFECT, 95% CONFIDENCE BOUNDS SECULAR TREND FIGURE 3. Effect of a community education program on definite in-hospital stroke rates among 30- to 4-year-old men and women in the Minnesota Heart Health Program (MHHP), All results are standardized to the mean population of subjects aged 30-4 years in the study communities. Left panel: Age-standardized event rates, pooled between communities using numbers of person-years in each community as weights. The rates were adjusted to provide a common mean level between educated and comparison communities during baseline and lag periods (E- through E2). Right panel: Fitted secular trend and annual MHHP effect estimates; bars, 95% confidence intervals. estimates, and further bias would arise from the shifting relative contribution of each pair in those partial years. We chose to use data weighted by person-years only if the partial year included at least 8 months of data for each of the two largest pairs. Second, only events validated as definite were used to calculate rates, although other events were recorded as possible events when they did not meet the full criteria for definite coronary heart disease or stroke. Because a combined analysis of definite plus possible events showed virtually the same results as those presented here, we limited this presentation to definite events. There are also two issues related to the regression analysis we used. We conducted analysis at the community level, fitting a regression model to the agestandardized annual rates from the six MHHP communities. Such an analysis is appropriate, given the allocation of intact communities to the intervention and comparison groups, and has been widely recommended (46-50). However, a common concern with such analyses is their low statistical power. In planning the study, we had projected 85 percent power to detect net differences in coronary heart disease mortality of 5- percent over 6 years, based on an analysis of men and women pooled, comparing the three intervention communities with the entire states of Minnesota, North Dakota, and South Dakota. The detectable difference for stroke mortality had been estimated to be about 35 percent over a 6-year period. As the analysis progressed, it became clear that the effects were different in men and women, such that pooling no longer made sense. In addition, as the modest differences emerged, it also became clear that there was little point in comparing the intervention communities with the three states, particularly when that analysis would be restricted to deaths based on unvalidated state death tapes. We knew that statistical power would be reduced for sex-specific analyses comparing the education and comparison communities alone. Now we believe that these analyses are more informative than those origi-

10 360 Luepker et al. nally envisioned. Given 80 percent statistical power and based on observed variations in the data, the detectable net differences over 5 years for coronary heart disease and stroke in the analyses reported here were 28.3 percent and 58.3 percent, respectively, for men and 49.6 percent and 62. percent, respectively, for women. While the power to detect 5- percent net differences was well below 85 percent, we do not attribute the results reported here to low power. Rather, they appear to be due to a lack of substantial, lasting differences between the intervention and comparison communities in levels of coronary heart disease risk factors and subsequent morbidity and mortality. In addition, the regression analysis assumed a common linear secular trend. This is important, because the imposition of a linear trend influenced the MHHP intervention effect estimates computed as yearspecific departures from that trend. A comparison of the left- and right-hand panels in figures 2 and 3 confirms that the model fitted the data reasonably well for stroke but less well for coronary heart disease. A paired-difference model would have avoided this problem, but it would have provided considerably less power (only df), would not have estimated the secular trend, and would have substituted one set of assumptions for another. Because any model is an imperfect simplification of the underlying data, we have shown both the left- and right-hand panels in figures 2 and 3, as well as the age-standardized rates presented in tables 4 and 5, to assist the reader in interpreting these results. Finally, we acknowledge that randomization was not employed in the MHHP design. Given the few communities in the study, simple randomization had little likelihood of achieving comparability between the intervention and comparison areas. More recent trials have used a greater number of units (5); under these conditions, randomization has a greater Likelihood of achieving comparability between intervention and comparison areas. In the MHHP, adjustment was possible for some baseline characteristics that should have been balanced by randomization (sex and age distributions and disease incidence rates). Other characteristics of the communities that were potentially important to the outcome (e.g., educational level) could not be considered. Conclusions The Minnesota Heart Health Program was launched during a decade of strongly declining secular trends in cardiovascular disease risk in Minnesota and nationally. Although individual elements of the intervention programs had the effects intended (30-33), the program as a whole did not accelerate risk reduction beyond those trends. However, the MHHP, along with related programs in California () and Rhode Island (3), has influenced national programs and policies. 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12 362 Luepker et al. APPENDIX TABLE. Numbers of definite coronary heart disease event* (fatal and nonfatal combined) in men and women aged 30-4 years when the event occurred, Minnesota Heart Health Program, Education year Community E-3 E-2 E- EO E E2 E3 E4 E5 E6 Men Fargo-Moorhead 4f 3f * 9* Woman Fargo-Moorhead lit 2f * 2* * During a 0-month period, t During an 8-month period. APPENDIX TABLE 2. Numbers of definite stroke events (fatal and nonfatal combined) in men and women aged 30-4 years when the event occurred, Minnesota Heart Hearth Program, Education year Community E-3 E-2 E- EO E E2 E3 E4 E5 E6 Man Fargo-Moorhead 2f t 2 5* 9* Women Fargo-Moorhead * During a 0-month period, t During an 8-month period. lit 2f * 5*