Strategies of prevention revisited: effects of imprecise measurement of risk factors on the evaluation of "high-risk" and "population-based" approaches to prevention of cardiovascular disease

Death burden of high systolic blood pressure in Sichuan Southwest China 1990-2030

BACKGROUND

Hypertension is highly prevalent and is the primary risk factor for cardiovascular disease (CVD) and chronic kidney disease (CKD). While declining in some developed countries, it is increasing rapidly in some developing countries. Sichuan province is the largest and underdeveloped region in southwest China, with 486 thousand square kilometers, more than 80 million residents, unbalanced economic development, and high prevalence, low awareness, low treatment and low control rate of hypertension. We forecasted the death burden due to high systolic blood pressure (SBP) in Sichuan from 1990 to 2030, to raise the awareness of public and government of the importance and benefits of hypertension control.

METHODS

We conducted secondary analysis based on data of Global Burden of Disease (GBD) 1990-2015, and predicted the population SBP level, population attributable fraction, and death burden for people aged 30-69 under different scenarios in 2030.

RESULTS

Comparing with natural trend, if the prevalence of high SBP can be reduced relatively by 25% by 2030, the deaths of non-communicable chronic diseases (NCDs), CVD and CKD would be reduced by 27.1 thousand, 26.2 thousand and 0.8 thousand for people aged 30-69; the mortality would be reduced by 10.8, 32.8 and 16.0%; and the premature mortality would be reduced by 9.9, 32.0 and 16.0%, respectively.

CONCLUSIONS

Controlling or decreasing the prevalence of high SBP can significantly reduce the deaths, death rate and premature mortality of NCDs, CVD and CKD for the 30-69 years old population in Sichuan. There would be huge benefits for the governments to take cost-effective measures to control or reduce the prevalence of hypertension.

Long-Term Exposure to Elevated Systolic Blood Pressure in Predicting Incident Cardiovascular Disease: Evidence From Large-Scale Routine Electronic Health Records

Background How measures of long-term exposure to elevated blood pressure might add to the performance of "current" blood pressure in predicting future cardiovascular disease is unclear. We compared incident cardiovascular disease risk prediction using past, current, and usual systolic blood pressure alone or in combination. Methods and Results Using data from UK primary care linked electronic health records, we applied a landmark cohort study design and identified 80 964 people, aged 50 years (derivation cohort=64 772; validation cohort=16 192), who, at study entry, had recorded blood pressure, no prior cardiovascular disease, and no previous antihypertensive or lipid-lowering prescriptions. We used systolic blood pressure recorded up to 10 years before baseline to estimate past systolic blood pressure (mean, time-weighted mean, and variability) and usual systolic blood pressure (correcting current values for past time-dependent blood pressure fluctuations) and examined their prospective relation with incident cardiovascular disease (first hospitalization for or death from coronary heart disease or stroke/transient ischemic attack). We used Cox regression to estimate hazard ratios and applied Bayesian analysis within a machine learning framework in model development and validation. Predictive performance of models was assessed using discrimination (area under the receiver operating characteristic curve) and calibration metrics. We found that elevated past, current, and usual systolic blood pressure values were separately and independently associated with increased incident cardiovascular disease risk. When used alone, the hazard ratio (95% credible interval) per 20-mm Hg increase in current systolic blood pressure was 1.22 (1.18-1.30), but associations were stronger for past systolic blood pressure (mean and time-weighted mean) and usual systolic blood pressure (hazard ratio ranging from 1.39-1.45). The area under the receiver operating characteristic curve for a model that included current systolic blood pressure, sex, smoking, deprivation, diabetes mellitus, and lipid profile was 0.747 (95% credible interval, 0.722-0.811). The addition of past systolic blood pressure mean, time-weighted mean, or variability to this model increased the area under the receiver operating characteristic curve (95% credible interval) to 0.750 (0.727-0.811), 0.750 (0.726-0.811), and 0.748 (0.723-0.811), respectively, with all models showing good calibration. Similar small improvements in area under the receiver operating characteristic curve were observed when testing models on the validation cohort, in sex-stratified analyses, or by using different landmark ages (40 or 60 years). Conclusions Using multiple blood pressure recordings from patients' electronic health records showed stronger associations with incident cardiovascular disease than a single blood pressure measurement, but their addition to multivariate risk prediction models had negligible effects on model performance.

A Double-Blind Placebo-Controlled Crossover Study of the Effect of Beetroot Juice Containing Dietary Nitrate on Aortic and Brachial Blood Pressure Over 24 h

Dietary inorganic nitrate in beetroot can act as a source of nitric oxide and has been reported to lower brachial blood pressure (BP). This study examined the effect of inorganic nitrate in beetroot juice on aortic (central) BP acutely and over the subsequent 24-h period. A double blind, randomized, placebo-controlled crossover trial was performed in fifteen healthy, normotensive men and women (age 22–40 years). Participants were randomized to receive beetroot juice containing nitrate (6.5–7.3 mmol) or placebo beetroot juice from which nitrate had been removed (<0.06 mmol nitrate). Effects on aortic systolic BP were measured at 30 min (primary endpoint), 60 min and over a subsequent 24 h period using an ambulatory BP monitor. Carotid-femoral pulse wave velocity (cfPWV) was also measured at 30 min. Following a washout period, the procedure was repeated within 7 days with crossover to the opposite arm of the trial. Compared with placebo, ingestion of beetroot juice containing nitrate lowered aortic systolic BP at 30 min by 5.2 (1.9–8.5) mmHg [mean (95% confidence interval); p < 0.01]. A smaller effect on aortic systolic BP was observed at 60 min. There were minimal effects on brachial BP or cfPWV. Effects on aortic systolic BP were not sustained over the subsequent 24 h and there were no effects on other hemodynamic parameters during ambulatory monitoring. A single dose of beetroot juice containing nitrate lowers aortic BP more effectively than brachial BP in the short term, but the effects are comparatively short-lived and do not persist over the course of the same day.

Optimal strategies for monitoring lipid levels in patients at risk or with cardiovascular disease: a systematic review with statistical and cost-effectiveness modelling

BACKGROUND

Various lipid measurements in monitoring/screening programmes can be used, alone or in cardiovascular risk scores, to guide treatment for prevention of cardiovascular disease (CVD). Because some changes in lipids are due to variability rather than true change, the value of lipid-monitoring strategies needs evaluation.

OBJECTIVE

To determine clinical value and cost-effectiveness of different monitoring intervals and different lipid measures for primary and secondary prevention of CVD.

DATA SOURCES

We searched databases and clinical trials registers from 2007 (including the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, the Clinical Trials Register, the Current Controlled Trials register, and the Cumulative Index to Nursing and Allied Health Literature) to update and extend previous systematic reviews. Patient-level data from the Clinical Practice Research Datalink and St Luke's Hospital, Japan, were used in statistical modelling. Utilities and health-care costs were drawn from the literature.

METHODS

In two meta-analyses, we used prospective studies to examine associations of lipids with CVD and mortality, and randomised controlled trials to estimate lipid-lowering effects of atorvastatin doses. Patient-level data were used to estimate progression and variability of lipid measurements over time, and hence to model lipid-monitoring strategies. Results are expressed as rates of true-/false-positive and true-/false-negative tests for high lipid or high CVD risk. We estimated incremental costs per quality-adjusted life-year.

RESULTS

A total of 115 publications reported strength of association between different lipid measures and CVD events in 138 data sets. The summary adjusted hazard ratio per standard deviation of total cholesterol (TC) to high-density lipoprotein (HDL) cholesterol ratio was 1.25 (95% confidence interval 1.15 to 1.35) for CVD in a primary prevention population but heterogeneity was high (I(2) = 98%); similar results were observed for non-HDL cholesterol, apolipoprotein B and other ratio measures. Associations were smaller for other single lipid measures. Across 10 trials, low-dose atorvastatin (10 and 20 mg) effects ranged from a TC reduction of 0.92 mmol/l to 2.07 mmol/l, and low-density lipoprotein reduction of between 0.88 mmol/l and 1.86 mmol/l. Effects of 40 mg and 80 mg were reported by one trial each. For primary prevention, over a 3-year period, we estimate annual monitoring would unnecessarily treat 9 per 1000 more men (28 vs. 19 per 1000) and 5 per 1000 more women (17 vs. 12 per 1000) than monitoring every 3 years. However, annual monitoring would also undertreat 9 per 1000 fewer men (7 vs. 16 per 1000) and 4 per 1000 fewer women (7 vs. 11 per 1000) than monitoring at 3-year intervals. For secondary prevention, over a 3-year period, annual monitoring would increase unnecessary treatment changes by 66 per 1000 men and 31 per 1000 women, and decrease undertreatment by 29 per 1000 men and 28 per 1000 men, compared with monitoring every 3 years. In cost-effectiveness, strategies with increased screening/monitoring dominate. Exploratory analyses found that any unknown harms of statins would need utility decrements as large as 0.08 (men) to 0.11 (women) per statin user to reverse this finding in primary prevention.

LIMITATION

Heterogeneity in meta-analyses.

CONCLUSIONS

While acknowledging known and potential unknown harms of statins, we find that more frequent monitoring strategies are cost-effective compared with others. Regular lipid monitoring in those with and without CVD is likely to be beneficial to patients and to the health service. Future research should include trials of the benefits and harms of atorvastatin 40 and 80 mg, large-scale surveillance of statin safety, and investigation of the effect of monitoring on medication adherence.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013003727.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

From exposures to population interventions: pregnancy and response to HIV therapy

Many epidemiologic studies identify contrasts between an "always-exposed" population and a "never-exposed" population. Such "exposure effects" are perhaps most valuable in discussing individual lifestyle changes, or in clinical care; they may be less valuable in estimating the potential effects of realistic public health interventions. Various methods, among them population attributable fractions and generalized impact fractions, attempt to obtain more policy-relevant estimates of "population intervention" effects, but such methods remain rare in the epidemiologic literature. Here, we describe the use of the parametric g-formula as a tool for the estimation of population intervention effects in longitudinal data. Our discussion is motivated by a previous study of the effect of incident pregnancy on time to virological failure among human immunodeficiency virus-positive women initiating antiretroviral therapy in South Africa between 2004 and 2011. We show that 1) interventional estimates of effect can be estimated in longitudinal data using the parametric g-formula and 2) exposure effects and population interventional effects can have dramatically different interpretations and magnitudes in real-world data. Epidemiologists should consider estimating interventional effects in addition to exposure effects; doing so would allow the results of epidemiologic studies to be more immediately relevant to policy-makers and to implementation science efforts.

A comparison of outcomes with coronary artery calcium scanning in unselected populations: the Multi-Ethnic Study of Atherosclerosis (MESA) and Heinz Nixdorf RECALL study (HNR)

BACKGROUND

The Multi-Ethnic Study of Atherosclerosis (MESA) and the Heinz Nixdorf RECALL (Risk factors, Evaluation of Coronary Calcium and Lifestyle Factors) study (HNR) differed in regard to informing physicians and patients of the results of their subclinical atherosclerosis.

OBJECTIVE

This study investigates whether the association of the presence of coronary calcium with incident nonfatal and fatal cardiovascular events is different among these 2 large, population-based observational studies.

METHODS

All white subjects aged 45 to 75 years, free of baseline cardiovascular disease were included (n = 2232 in MESA; n = 3119 HNR participants). We studied the association between coronary calcium and event rates at 5 years, including hard cardiac events (myocardial infarction, cardiac death, resuscitated cardiac arrest), and separately added revascularizations and strokes (fatal and nonfatal) to determine adjusted hazard ratios.

RESULTS

Both cohorts showed low coronary heart disease (including revascularization) rates with zero coronary calcium (1.13% and 1.16% over 5 years in MESA and HNR, respectively) and increasing significantly in both groups with Agatston score 100 to 399 (6.71% and 4.52% in MESA and HNR, respectively) and Agatston score > 400 (12.5% and 13.54% in MESA and HNR, respectively) and showing strong independent predictive values for Agatston scores of 100 to 399 and >400, despite multivariable adjustment for risk factors. Risk factor-adjusted 5-year revascularization rates were nearly identical for HNR and MESA and were generally low for both studies (1.4% [45 of 3119] for HNR and 1.9% [43 of 2232] for MESA) over 5 years.

CONCLUSIONS

Across 2 culturally diverse populations, Agatston score >400 is a strong predictor of events. High Agatston score did not statistically result in revascularization, and knowledge of the presence of coronary calcium did not increase revascularizations.

Effect of correcting for long-term variation in major coronary heart disease risk factors: relative hazard estimation and risk prediction in the Atherosclerosis Risk in Communities Study

PURPOSE

To examine the effect of correcting coronary heart disease (CHD) risk factors for long-term within-person variation on CHD risk.

METHODS

By using 5533 men and 7301 women from the Atherosclerosis Risk in Communities (ARIC) study, we compared models incorporating risk factors measured at a single visit and models incorporating additional measurements for systolic blood pressure, total cholesterol, and high-density lipoprotein cholesterol taken 3 years before baseline.

RESULTS

The largest change away from null was observed for systolic blood pressure, ie, hazard ratio (HR) 1.38 to 1.69 (+81%) in women and HR 1.26 to 1.41 (+56%) in men. HRs also decreased for age (-32% in women, -9% in men), race (-67% in women), the presence of diabetes (-13% in men and women), and medication use for hypertension (-27% in women, -26% in men) and cholesterol (-97% in women, HR 1.06-0.93 in men). The area under the ROC curve did not improve significantly in men or women, whereas reclassification was only significant in women (net reclassification improvement 5.4%, p = 0.016).

CONCLUSIONS

Modeling long-term variation in CHD risk factors had a substantial impact on HR estimates, with new effect estimates further from the null for some risk factors and closer for others including age and medication use, but only improved risk classification in women.

Effect of inter-reader variability on outcomes in studies using carotid intima media thickness quantified by carotid ultrasonography

Systematic differences between readers or equipment in imaging studies are not uncommon; failure to account for such differences when using Carotid Ultrasonography may introduce bias into associations between carotid intima media thickness (cIMT) and outcomes. We demonstrate the impact of this source of systematic measurement error (SME) using data on 5,521 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) and 661 participants from the Study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM). Participants were between 37 and 78 years old. Two outcomes were considered: (1) the effect of HIV infection on cIMT (between study) and (2) the association of cIMT with cardiovascular events (within study). All estimates were adjusted for demographics (age, gender, and ethnicity) and for traditional cardiovascular disease risk factors (smoking, blood pressure, diabetes and cholesterol). When comparing the FRAM and MESA cohorts to estimate the association of HIV infection on common cIMT, accounting for machine and reader variability (between study variability) reduced the difference associated with HIV infection from +0.080 mm (95% Confidence Interval (CI):0.065-0.095) to +0.037 mm (95% CI:0.003 to 0.072) while internal cIMT declined from +0.254 mm (95% CI:0.205-0.303) to +0.192 mm (95% CI:0.076-0.308). Attenuation of the association between cIMT and cardiovascular endpoints occurred when within study reader variability was not accounted for. The effect of SME due to use of multiple readers or machines is most important when comparisons are made between two different study populations. Within-cohort measurement error dilutes the association with events.

The relative merits of population-based and targeted prevention strategies

CONTEXT

Preventive medicine has historically favored reducing a risk factor by a small amount in the entire population rather than by a large amount in high-risk individuals. The use of multivariable risk prediction tools, however, may affect the relative merits of this strategy.

METHODS

This study uses risk factor data from the National Health and Nutrition Examination Survey III to simulate a population of more than 100 million Americans aged thirty or older with no history of CV disease. Three strategies that could affect CV events, CV mortality, and quality-adjusted life years were examined: (1) a population-based strategy that treats all individuals with a low- or moderate-intensity intervention (in which the low-intensity intervention represents a public health campaign with no demonstrable adverse effects), (2) a targeted strategy that treats individuals in the top 25 percent based on a single risk factor (LDL), and (3) a risk-targeted strategy that treats individuals in the top 25 percent based on overall CV risk (as predicted by a multivariable prediction tool). The efficiency of each strategy was compared while varying the intervention's intensity and associated adverse effects, and the accuracy of the risk prediction tool.

FINDINGS

The LDL-targeted strategy and the low-intensity population-based strategy were comparable for CV events prevented over five years (0.79 million and 0.75 million, respectively), as were the risk-targeted strategy and moderate-intensity population-based strategy (1.56 million and 1.87 million, respectively). The risk-targeted strategy, however, was more efficient than the moderate-intensity population-based strategy (number needed to treat [NNT] 19 vs. 62). Incorporating a small degree of treatment-related adverse effects greatly magnified the relative advantages of the risk-targeted approach over other strategies. Reducing the accuracy of the prediction tool only modestly decreased this greater efficiency.

CONCLUSIONS

A population-based prevention strategy can be an excellent option if an intervention has almost no adverse effects. But if the intervention has even a small degree of disutility, a targeted approach using multivariable risk prediction can prevent more morbidity and mortality while treating many fewer people.

Effect of a 4-year workplace-based physical activity intervention program on the blood lipid profiles of participating employees: The high-risk and population strategy for occupational health promotion (HIPOP-OHP) study

Individuals who are physically fit or engage in regular physical activity have a lower incidence of cardiovascular disease and risk of mortality. We conducted a large-scale controlled trial of interventions to decrease cardiovascular risk factors, during which we assessed the effect of a workplace-based intervention program, which was part of a population strategy for promoting long-term increases in physical activity, on the blood lipid profiles of participating employees. Data were collected from 2929 participants and this report presents the results of a survey conducted in five factories for the intervention group and five factories for the control group at baseline and year 5. The absolute/proportional changes in HDL-cholesterol were 2.7 mg/dL (4.8%) in the intervention group and -0.6 mg/dL (-1.0%) in the control group. The differences between the two groups in the change in serum levels of HDL-cholesterol were highly significant (p<0.001) in each analysis of covariance, in which the number of cigarettes smoked was included or excluded. In the intervention group, the daily walking time increased significantly (p<0.001) when compared between baseline and year 5, whereas no significant difference was observed in daily walking time in the control group over the identical period. Our results show that an intervention program promoting physical activity raises serum HDL-cholesterol levels of middle-aged employees. Increased awareness of the benefits of physical activity, using environmental rearrangement and health promotion campaigns, which especially target walking, may have contributed to a beneficial change in serum HDL-cholesterol levels in the participants.

Blood pressure and the global burden of disease 2000. Part II: estimates of attributable burden

OBJECTIVES

To provide estimates of the global burden of disease attributable to non-optimal blood pressure by age and sex for adults aged > or = 30 years, by WHO subregion.

METHODS

Estimates of attributable burden were made using population impact fractions, which used data on mean systolic blood pressure levels, disease burden [in deaths and/or disability-adjusted life years (DALYs)] and relative risk corrected for regression dilution bias. Estimates were made of burden attributable to a population distribution of blood pressure with a mean systolic blood pressure of greater than 115 mmHg.

RESULTS

Globally, approximately two-thirds of stroke and one-half of ischaemic heart disease were attributable to non-optimal blood pressure. These proportions were highest in the more developed parts of the world. Worldwide, 7.1 million deaths (approximately 12.8% of the global total) and 64.3 million DALYs (4.4% of the global total) were estimated to be due to non-optimal blood pressure. Overall approximately, two-thirds of the attributable burden of disease occurred in the developing world, approximately two-thirds in the middle age groups (45-69 years) and approximately one-half occurred in those with systolic blood pressure levels between 130 and 150 mmHg.

CONCLUSIONS

The burden of non-optimal blood pressure is almost double that of the only previous global estimates, which is largely explained by the correction for regression dilution adopted in these analyses. High blood pressure is a leading cause of global burden of disease, and most of it occurs in the developing world.

Screening for chronic kidney disease: unresolved issues

End-stage renal disease is epidemic in the United States. As a measure to control this epidemic, it has been recommended that individuals who are at risk for CKD be tested for undetected kidney disease during routine health care encounters. There are generally accepted criteria against which screening recommendations for CKD control and prevention programs should be judged. If detection strategies are to be adopted for the screening of kidney disease, then CKD must represent a significant public health problem, be characterized by a clear natural history with a detectable asymptomatic period, outcomes should be improved by early treatment, and acceptable screening tests should be available. Health systems must provide adequate and appropriate follow-up medical care for individuals with newly detected CKD. Finally, the cost-effectiveness of screening needs to be demonstrated and the effectiveness of screening as a means of achieving reductions in CKD should be proven in randomized trials.

Estimating the prevalence of hypertension corrected for the effect of within-person variability in blood pressure

The objective of our study was to assess the applicability of using estimates of within-person variance (WPV) from reproducibility studies for a correction of blood pressure values in another study to improve the accuracy of the prevalence estimation of hypertension. Data were collected from two cross-sectional population-based studies on cardiovascular disease risk factors conducted from 1987 to 1995 among 55,026 subjects aged 20-59 years. Correction factors were calculated from a reproducibility study among 924 subjects who were examined in 1989 and 1990. All other studies with repeated measurements of blood pressure were searched in MEDLINE from 1966 onward. Six studies satisfied the inclusion criteria. The prevalence of hypertension, uncorrected and corrected with factors from other studies, were compared with the prevalence of hypertension corrected with the factor from our study. The uncorrected prevalence of hypertension was 17.3% [95%CI:17.0-17.7]. The prevalence of hypertension after correction for WPV with the factor from our study was 13.5% [95%CI:13.2-13.8]. Correction for WPV with factors from the appropriate studies (depending on factors such as number of measurements taken per visit, and time interval between visits) resulted in prevalences ranging from 13.9% to 14.7%. The bias that occurs when no correction for WPV is performed is much larger (29% overestimation) than the bias that occurs when correction factors are derived from other studies (3.1-8.4% overestimation). When repeated measurements of blood pressure are not available in a population study for a sample of that same study, it is advisable to use data from another study to correct for WPV.

Blood pressure and the global burden of cardiovascular disease

Cardiovascular disease is responsible for a large and increasing proportion of death and disability worldwide. Half of this burden occurs in Asia. This study assessed the possible effects of population-wide (2% lower DBP for all) and targeted (7% lower DBP for those with usual DBP > or = 95 mmHg) BP interventions in Asia, using data from surveys of blood pressure levels, the Global Burden of Disease Project, Eastern Asian cohort studies and randomised trials of blood pressure lowering. Overall each of the two interventions would be expected to avert about one million deaths per year throughout Asia in 2020. These benefits would be approximately additive. About half a million deaths might be averted annually by each intervention in China alone, with about four-fifths of this benefit due to averted stroke. The relative benefits of these two strategies are similar to estimates made for US and UK populations. However, the absolute benefits are many times greater due to the size of the predicted CVD burden in Asia.

Undertreatment of hypertension in a population-based study in The Netherlands

OBJECTIVE

To estimate the level of undertreatment of hypertension in a population-based study by taking into account the co-existence of additional cardiovascular risk factors in untreated hypertensives, uncontrolled blood pressure among pharmacologically treated hypertensives and within-person variability in blood pressure and total cholesterol.

DESIGN

Cross-sectional.

SETTING

Two population-based surveys on cardiovascular disease risk factors conducted during 1987-1995 in The Netherlands.

PARTICIPANTS

56 026 men and women aged 20-59 years.

MAIN OUTCOME MEASURES

Prevalence of hypertension, of treatment and of undertreatment of hypertension. Undertreated hypertensives were those who were treated pharmacologically, but whose blood pressure was still elevated and those who inappropriately received no medication for the treatment of hypertension.

RESULTS

During the past decade in The Netherlands, 30% of the hypertensive women and 47% of the hypertensive men aged 20-59 years were undertreated for hypertension. In both men and women treated pharmacologically, 42 and 29%, respectively, still had elevated blood pressure levels. Of those hypertensive men and women not treated pharmacologically, 53 and 34%, respectively, should have been treated when additional cardiovascular risk factors were taken into account Among those diagnosed but untreated for hypertension, 58 and 31% of the men and women, respectively, should have been treated pharmacologically.

CONCLUSION

A considerable proportion of hypertensives were undertreated for hypertension. To decrease the undertreatment of hypertension, it is necessary to obtain better control of blood pressure in patients already being treated, increase the detection of hypertension and improve adherence to the current guidelines.

Economic evaluation of cholesterol-related interventions in general practice. An appraisal of the evidence

STUDY OBJECTIVE

To investigate and evaluate published data on cost effectiveness of cholesterol lowering interventions, and how this information could be interpreted in a rational approach of cholesterol management in general practice.

DESIGN

A systematic review of the literature.

SETTING

No restriction on setting.

MATERIALS

Papers reporting on the cost effectiveness or cost utility of prevention of (recurrent) coronary heart disease by reduction of hypercholesterolaemia in adults.

MAIN RESULTS

Thirty nine studies, most cost effectiveness analyses, were included. In 24 studies drug interventions only were analysed. Costs of screening to target cholesterol lowering interventions to persons with hypercholesterolaemia were considered in nine studies. Adjustments of the efficacy of the intervention for community effectiveness were described in seven studies. In four studies life years gained were adjusted for quality of life. Despite large variation in the outcomes, there is a constant tendency towards a less favourable cost effectiveness ratio for intervening in persons without coronary heart disease compared with persons with coronary heart disease and for women compared with men.

CONCLUSIONS

There is lack of data on cost effectiveness of cholesterol lowering interventions in the general practice setting. The cost effectiveness of cholesterol lowering in general practice deteriorates when all relevant costs are taken into account and when efficacy is corrected for community effectiveness. Cholesterol lowering intervention is more cost effective in men compared with women and in patients with coronary heart disease compared with persons without coronary heart disease. Considerations from cost effectiveness analyses should be incorporated into the development and implementation of national cholesterol guidelines for general practitioners. Standardisation of cost effectiveness studies is important for future economic evaluations.

Variation in reported prevalences of hypertension in The Netherlands: the impact of methodological variables

STUDY OBJECTIVE

To estimate the prevalence of hypertension in The Netherlands and to quantify the influence of methodological variables on the reported prevalences.

DESIGN

A pooled analysis was performed based on reported age specific prevalences of hypertension. A logistic model was used to estimate the probability of hypertension.

MAIN RESULTS

The age standardised prevalence of hypertension varies more than fivefold between studies carried out in The Netherlands. The probability of having hypertension was lower if blood pressure was measured at more than one point in time (Odds ratio 0.44 (OR) (95% confidence interval (95% CI) 0.38, 0.51) for men and 0.47 (0.41, 0.54) for women, and if the study was carried out more recently (OR 0.92 (0.91, 0.93) per year). The probability was higher if the study was carried out in a general practice (OR 1.14 (1.03, 1.27) for men and 1.52 (1.36, 1.69) for women). The inclusion of treated people as hypertensive yields contradictory results for men and women.

CONCLUSIONS

The strong variation in prevalence is explained by methodology and by a period effect indicating a decrease of the prevalence of hypertension over time. Whether this decrease is true or caused by confounding due to unknown or unreported methodological variation over time is unknown. For future studies, a standardised method could reduce the influence of methodological variables and thereby the variation in reported prevalences.

Feasibility study of N-of-1 trials with blood pressure self-monitoring in hypertension

The objective of this study was to assess individual responses to antihypertensive treatment by N-of-1 trials using blood pressure self-monitoring in 79 patients of both sexes referred to a hypertension clinic. Thirty-five patients who remained untreated (study 1) and 44 N-of-1 trial participants (study 2) were consecutively selected if their clinic blood pressure was between 160/95 and 220/115 mm Hg and there were no hypertensive complications. Blood pressure was measured daily at home for 21 days (three consecutive measures, morning and evening). Each N-of-1 trial was a single-blind treatment consisting of two successive 10-day treatment pairs, each pair comprising 5 days of placebo followed by 5 days of 20 mg enalapril once daily in the morning. Study 1 showed no significant blood pressure regression toward the mean over 20 days and justified the choice of 5-day treatment periods in study 2. In study 2, blood pressure fell significantly 12 hours after the first administration of enalapril and rose within 24 hours of the end of the 5-day active treatment period. Using evening blood pressure values (12 hours after enalapril intake) from the first treatment pair, 33 patients were classified as responders (diastolic blood pressure fall > or = mm Hg). In 16 of these 33 patients, the fall in blood pressure above 6 mm Hg was not maintained in the morning, 24 hours after drug intake. Response reproducibility was tested by comparison with the second treatment pair: the observed agreement was only 0.71 (chance-corrected agreement: 0.34) when defined according to both evening and morning values.(ABSTRACT TRUNCATED AT 250 WORDS)