We have demonstrated that clinically important increases in body weight begin at least 1 week before hospitalization for heart failure. Moreover, during this time period, the risk of heart failure hospitalization increases in a monotonic fashion with increasing amounts of weight gain. In contrast, weight gain was not observed before hospitalization for causes other than heart failure. The present study represents basic clinical research that generates evidence to guide decision making for surveillance of weights in patients with heart failure.
The results of the present study can be viewed as a confirmation of “conventional wisdom” on weight gain preceding hospitalization for heart failure, because weight gain as a potential precipitant for hospitalization has not been demonstrated conclusively. The present results indicate that weight gain is an important risk factor for hospitalization within a relatively short time period. Prior studies have had mixed results with regard to the effectiveness of remote weight monitoring in improving outcomes for patients with heart failure.8
Because the weight-monitoring interventions in those studies were implemented with variable methods (eg, self-reported weight versus automatic transmission of weight as in the present study), frequency, and duration and with very different patient populations, a lack of consistent findings is perhaps not surprising. Although recent studies have used invasive measurements of thoracic impedance and pulmonary artery pressures,9
the published literature does not allow for direct comparisons with the present data.
Heart failure is the most frequent reason for hospitalization among older patients,10
with direct hospital costs of more than $15.4 billion each year.11
The burden that heart failure hospitalization imposes on patients and their caregivers is also substantial. The present results, which support current recommendations from professional groups about the importance of self-weighing for heart failure patients,12
indicate that clinicians have an opportunity to intervene (eg, by increasing diuretic doses) and possibly avert hospitalization.
The “real-world” applicability of the results of the present study is reflected by data that come from actual patients participating in a home monitoring system, rather than a clinical trial with strict inclusion-exclusion criteria and complex follow-up procedures. Similar to heart failure patients seen in clinical practice, the majority of study participants were elderly. The validity of the present results is strengthened by the lack of association between weight gain and hospital admission for reasons other than heart failure and by the small amount of missing data on body weight. Importantly, the present analyses were matched on, and adjusted for, potential confounding factors that could have introduced bias, including baseline body weight.
Participation in the home monitoring system was voluntary, and we do not have information about the number of patients who declined participation; it is possible that the present results were affected by patients' refusal to participate. Information was not available about type of heart failure (systolic versus diastolic) or presence of renal dysfunction, and it is possible that differences in these important clinical characteristics contributed to the weight patterns observed and hospitalization rates. Recent work suggests, however, that the rate of heart failure hospitalization is similar in patients with diastolic and systolic heart failure.13,14
Most patients in the present study had NYHA class III heart failure, which reflects the distribution of heart failure severity among patients participating in the monitoring system. Patients with NYHA class I and II heart failure may not have been deemed sick enough to justify the cost of the monitoring system, whereas those with NYHA class IV heart failure may have been deemed too sick to benefit from this system. Whether the present results may be generalized to patients with mild or severe heart failure is therefore uncertain.
Information was not available on how clinicians used the weight data, including attempts that may have been made to address weight gain (such as increasing diuretic dosage). It is possible that patients who experienced a significant weight gain but were not yet ill enough to require hospitalization had an increase in their diuretic dosage or received some other type of intervention. Such interventions would, however, bias the study toward a null finding. Alternatively, it is possible that weight gain played a role in the decision for hospitalization, but it seems unlikely that clinicians would hospitalize patients solely because of weight gain, without other signs and symptoms of clinical decompensation. Whatever impact clinicians' review of these data may have had on the results, significant differences between case and control patients in weight change were still observed. It is probable that the association between weight gain and hospitalization would be even stronger for patients in whom weight data were not being reviewed, and responded to with intervention, by clinicians.
The outcome in the present study (ie, heart failure hospitalization), was assessed by a nurse employed by Alere, Inc, during telephone interviews with patients. We do not have data to validate the accuracy of the outcome assessment, but a recent report suggests that concordance between self-reported and claims-based hospitalizations is high.15
Although all patients using the monitoring system were contacted via telephone by Alere staff to assess the outcomes used in the present study, we do not have data on the completeness of follow-up (ie, how often patients could not be reached to ascertain the outcome).
These data demonstrate that, on average, weight gain begins in a gradual fashion at least 1 week before heart failure hospitalization, but the present findings do not indicate that all admissions are preceded by weight gain. Some patients would have certainly experienced sudden decompensation with “flash” edema. For these episodes of decompensation, remote monitoring may prove less effective in averting hospitalization. In addition to weight gain, patients with heart failure may experience a range of other symptoms as manifestations of heart failure decompensation, including shortness of breath, fatigue, and leg swelling. The relative prognostic utility of such symptoms compared with body weight should be investigated in future studies.
Frequent monitoring of heart failure patients' clinical status, specifically their body weights, can alert clinicians to the early stages of heart failure decompensation. By focusing on weight changes, clinicians would be well positioned to implement interventions that could prevent decompensation of heart failure that necessitates hospitalization. To determine whether this type of monitoring system can improve outcomes, 2 study authors (SIC and HMK) are currently conducting a multicenter randomized, controlled trial that implements daily remote monitoring of body weight. Any weight gain >2 pounds triggers clinical assessment and potential intervention, including dietary advice, medication adjustment, and clinic or emergency department visit. The intervention is being implemented and all outcomes are being assessed during the 6 months after hospitalization for heart failure decompensation. More than 1600 patients from 20 sites across the country will be enrolled, which makes this one of the largest studies of remote monitoring to date. Systems to facilitate frequent monitoring of heart failure patients' clinical status have potential for improving the care and outcomes of patients with heart failure, but the emerging field of remote monitoring must be informed by evidence to guide clinicians in decision making.
Systems to enhance remote monitoring of patients' clinical status have the potential to improve the care and outcomes of patients with heart failure. Weight gain has long been recognized by clinicians as a marker of heart failure decompensation, but little information is available to quantify the relationship between weight change in patients with heart failure and the risk for imminent hospitalization. Accordingly, we evaluated data from a group of heart failure patients who were weighing themselves daily as part of a disease-management remote-monitoring system. Using a nested case-control study design, we matched 134 case patients with heart failure hospitalization to 134 control patients without heart failure hospitalization. The results demonstrate that increases in body weight are associated with hospitalization for heart failure and begin at least 1 week before admission. Within the week before hospitalization, the risk of heart failure hospitalization increases in a monotonic fashion with increasing amounts of weight gain. Any weight gain of >2 pounds is associated with increased risk of heart failure hospitalization. Our results indicate that weight gain is an important risk factor for hospitalization within a relatively short time period. Daily information about patients' body weight can alert clinicians to patients who are at high risk for hospitalization on the basis of weight gain. Equipped with this information, clinicians can implement interventions to try to avert hospitalization.