Do the Trajectories of Dyspnea Differ in Prevalence and Intensity By Diagnosis at the End of Life? A Consecutive Cohort Study

Article Outline

• Abstract
• Introduction
• Methods
  • Study Setting
  • Study Population and Design
  • Data Collection From Silver Chain Hospice Care Service Records
  • Data Analyses
  • Sensitivity Analysis
• Results
  • Descriptive Data of the Cohort
  • Overall Prevalence and Severity
  • Cancer/Noncancer Comparison of Intensity of Breathlessness by Time
  • Prevalence and Severity of Breathlessness by Diagnosis as Death Approaches
  • Sensitivity Analysis
• Discussion
  • Strengths of This Study
  • Limitations
    • Methods
    • Sample
  • Implications for Research
  • Implications for Practice
• Conclusions
• References
• Copyright

Abstract 

Context

Breathlessness reportedly worsens as death approaches for many people, but the differences in intensity and time course between underlying causes are not well described.

Objectives

To determine differences in the intensity of breathlessness by diagnosis over time as death approaches in a consecutive cohort seen by a specialist palliative care service.

Methods

Patients referred to Silver Chain Hospice Care Service over a period of four years (January 2004 to December 2007) had dyspnea evaluated at every clinical encounter until death. A numeric rating scale (NRS) was used to measure the intensity. Patients were categorized into five clusters (lung cancer, secondary cancer to lung, heart failure, end-stage pulmonary disease, and no identifiable cardiorespiratory cause) at three time points (60–53 [T₃], 30–23 [T₂], and 7–0 [T₁] days before death [T₀]). Group differences were assessed using analysis of variance. Joinpoint regression models defined significant changes in mean breathlessness intensity.

Results

For 5,862 patients, data were collected an average of 20 times (median: 13; 116,982 data points) for an average of 86 days (median: 48). Breathlessness was significantly higher at all three time points in people with noncancer diagnoses. Breathlessness increased significantly at days 10 and 3 before death for people with cancer (P<0.001 for both), but remained unchanged, albeit significantly higher for patients with noncancer diagnoses. In the three months leading to death, the prevalence of “no breathlessness” decreased from 50% to 35%, and the proportion of patients with severe breathlessness (>7 out of 10) increased from 10% to 26%.

Conclusion

Prevalence of breathlessness increases rapidly at life's end, especially for people with primary lung cancer; the levels of breathlessness became close to those experienced by people with noncancer diagnoses despite symptom control measures.

Key Words: Dyspnea, cancer, chronic disease, palliative care, chronic obstructive pulmonary disease, respiratory/pulmonary

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Introduction 

Significant dyspnea is frequently encountered across the community population¹ and is more common in advanced illnesses. Several authors have described the prevalence of breathlessness in patients with advanced cancer,², ³, ⁴, ⁵, ⁶, ⁷ but much less attention has been paid to other underlying life-limiting illnesses that are likely to cause breathlessness.⁸ Like fatigue, dyspnea worsens as death approaches and is frightening to patients, their caregivers, and the health professionals providing care for them.⁹, ¹⁰, ¹¹, ¹² Additionally, dyspnea is responsible for high numbers of emergency department presentations and hospitalizations.

Although there has been careful documentation of the worsening of dyspnea over time, there has been less emphasis on the way the underlying diagnosis influences the prevalence and intensity of breathlessness as death approaches. Such data have implications for clinical care, service planning, and to understand better the mechanisms driving the sensation of breathlessness. Understanding the progression of breathlessness over time stratified by the life-limiting diagnosis is crucial to ensure that adequate and timely evidence-based interventions are offered expectantly to people at high risk of developing symptomatic dyspnea as illness progresses.¹³, ¹⁴, ¹⁵

Recent work has suggested that the longitudinal progression of breathlessness may be different depending on the underlying life-limiting illness. These data have suggested that patients who have cardiorespiratory life-limiting illnesses have more severe levels of breathlessness than patients with cancer as they enter the palliative phase of their illness, and this is maintained through the terminal phase.

The aim of the study was to understand better the clinical course of breathlessness as death approached, by diagnosis in a consecutive cohort of people referred to a large regional metropolitan palliative care service. The objectives of the study were to understand the prevalence, intensity, and progression of breathlessness across a community palliative care population, including people with cancer and noncancer diagnoses, by the specific underlying life-limiting etiology (e.g., heart failure, chronic pulmonary disease, cancer [primary or metastatic], or no obvious cardiorespiratory source of dyspnea). The second aim was to develop a regression model to predict the key points at which the intensity of breathlessness changed in broad diagnostic groups. The null hypothesis was that there were no differences in the way that breathlessness was experienced as a result of the primary life-limiting illness.

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Methods 

Study Setting 

Silver Chain Hospice Care Service (SCHCS) is the sole regional community palliative care program covering all of the metropolitan area of Perth, Western Australia. The SCHCS uses an interdisciplinary model of care provision. The team comprises general practitioners, registered nurses, care aides, volunteers, counselors, and pastoral care workers. Registered nurses are available 24 hours/day, seven days/week, with support available after hours from the general practitioners and clinical nurse consultants. The service receives approximately 1,500 referrals annually for palliative care and is free of charge to patients with life-limiting illnesses, provided through state and federal health care funds.

Study Population and Design 

The study used data from a consecutive cohort of 5,862 patients seen by SCHCS over a four-year period beginning January 2004. The population and methods have been described previously.¹⁶, ¹⁷ The subgroup of interest had breathlessness at any time between referral to the service and subsequent death. The study was approved by Silver Chain Human Research Ethics Committee, a National Health and Medical Research Council compliant committee.

Data Collection From Silver Chain Hospice Care Service Records 

All data were collected in the clinical setting contemporaneously with each face-to-face visit by a health professional from the SCHCS, and processes, including staff recording of patient ratings of symptoms, remained constant over the life of the study period. De-identified data collected included the following:

Data quality was optimized by point-of-care data entry by SCHCS staff into mobile phone data systems for all data relating to that clinical encounter, which is used in routine clinical practice at SCHCS. Missing data were omitted from the specific analysis in question, as no imputed values were generated.

Data Analyses 

The population and service characteristics are reported using descriptive statistics. The primary comparator groups were composed of those people who did and did not develop breathlessness during the course of their life-limiting illness. The secondary comparators were the onset and intensity of breathlessness over time as death approached, stratified by lung cancer (primary or secondary) and other diagnoses subsequently broken down into cardiac failure, documented respiratory failure, or no obvious cardiorespiratory cause.

As a referral-dependent service, the only time point that is constant in hospice and palliative care is death.²¹ For this reason, the longitudinal analysis was constructed backward from the time of death. Time was anchored at death for T₀. Prevalence and subsequent incidence of dyspnea were charted against time by the week before death, in which the score was collected for the whole population (Fig. 1). Three time points before death were chosen to evaluate change over time, and where a sufficient number of people would have data available. The presence of breathlessness was then plotted for the five diagnostic groups. Intensity of breathlessness was also plotted backward from the time of death by the same groups at the four levels of intensities: 0, greater than 0–3, 4–6, and 7–10.

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• Fig. 1 

  Percentage of people with no, mild, moderate, or high dyspnea scores in a consecutive cohort of people referred to a community palliative care service as death approaches (n=5,862).

Univariate analyses used Chi-squared analyses for categorical data and analysis of variance for continuous variables. A statistically significant finding was accepted if P<0.05, modified, where appropriate, for multiple comparisons using a Bonferroni correction.

The analysis used a joinpoint regression model to determine the time points at which significant changes in the intensity of breathlessness were encountered in people with and without cancer (Joinpoint Regression Analysis, Version 3.3.1, April 2008; Statistical Research and Applications Branch, National Cancer Institute, Bethesda, Maryland, USA). Data were otherwise analyzed using Stata Version 10.1 statistical analysis software (Stata Corporation, 2005, College Station, TX). Missing data were left without an imputed value, as there was no way of generating such values.

Sensitivity Analysis 

All analyses were carried out for the whole population and for those who recorded breathlessness at some time to establish whether the trend and magnitude of effect were similar.

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Results 

Descriptive Data of the Cohort 

The study used data from a consecutive cohort of 5,862 patients referred to SCHCS between January 2004 and December 2007. On average, patients were seen a mean of 20 times between referral and death by the community palliative care team over, on average, an 86-day period, generating 116,982 data points. The data on breathlessness were collected by clinical nurse specialists (Table 1).

Table 1. Patient Characteristics of a Consecutive Cohort of People Referred to Silver Chain Hospice Care Service Between January 2004 and December 2007 (n=5,862)

Overall Prevalence and Severity 

Three months from death, one in two patients had no breathlessness. The percentage with no breathlessness fell to 35% at the time of death (Fig. 1). During the same time, severe breathlessness (≥7 out of 10) increased from less than 10% three months from death to more than 26% at the time of death. Only 671 out of 5,862 (11.4%) individuals had only “no breathlessness” recorded between referral and death.

Cancer/Noncancer Comparison of Intensity of Breathlessness by Time 

Aggregating noncancer diagnoses, this group was, on average, four years older than the cohort with cancer and had a significantly higher proportion of males (Table 2). Comparing breathlessness scores for patients with noncancer diagnoses with those of people with cancer, the differences in the perception of breathlessness were demonstrably different (Table 3). Patients with noncancer causes had significantly higher levels of breathlessness for the last three months of life. In contrast, patients with cancer had significantly lower levels of breathlessness initially, but there was an increase in breathlessness mostly in the last 10 days of life.

Table 2. Differences in Age, Gender, and Severity of Breathlessness By Diagnosis at Three Time Points

Characteristic	Cancer (n=5,386)	Noncancer (n=476)	P-value
Age
Mean (SD)	69.33 (13.84)	73.72 (20.95)	<0.001
Median (range)	71 (0–104)	78 (0–108)
% Male	53.1	56.7	0.034
	Male (%)	Female (%)
… and cancer
% With low/no breathlessness
T3	24.6	25.4	0.752
T2	37.4	36.6
T1	38.0	37.9
… and non-cancer
% With low/no breathlessness
T3	32.1	25.2	0.05
T2	44.1	40.3
T1	23.8	29.1
	<65 Years (%)	≥65 Years (%)
… and cancer
% With low/no breathlessness
T3	24.6	25.2	0.625
T2	37.9	36.6
T1	37.5	38.2
… non-cancer
% With low/no breathlessness
T3	33.4	30.4	0.001
T2	44.9	41.3
T1	21.7	28.6

T₁=7–0 days before death; T₂=23–30 days before death; and T₃=53–60 days before death.

Table 3. Comparison of cancer / non-cancer breathlessness scores collected at each clinical visit at three time points before death using all available data (n=5862)

Characteristics	Days Before Death			P-value of change across time within groups
	T3 (60–53)	T2 (30–23)	T1 (7–0)
Mean breathlessness scores; standard deviation; Median
Cancer	1.82	2.08	2.80	<0.001
n=5386	2.36	2.53	2.91
	0	1	2
Non-cancer	4.78	4.16	4.00	0.023
n=476	3.07	3.10	3.36
	5	4	4
P-value between cancer / non-cancer	<0.001	<0.001	<0.001

Using a joinpoint regression model for people with cancer, there were significant changes in the slope of the breathlessness curves between three and 10 days before death (P<0.001) and in the final three days before death (P<0.001) (Fig. 2). By contrast, the group with noncancer causes had no significant changes in the slope of the breathlessness graphs during the last three months of life but, at all times, had much more severe breathlessness.

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• Fig. 2 

  Joinpoint regression model of mean Symptom Assessment Scale (SAS) score of breathlessness by cancer and noncancer diagnoses at the approach of death in a consecutive cohort of 5,862 community palliative care patients.

Considering both gender and age, the only groups that demonstrated significant differences in trend for “no breathlessness” or low levels of breathlessness (0–3 out of 10) in the last three months of life were those comprising females and people older than 65 years with non-cancer diagnoses (Table 2).

Prevalence and Severity of Breathlessness by Diagnosis as Death Approaches 

Mean breathlessness scores increased across the population as death neared (Table 4, Fig. 3). Categorizing the data into five broad diagnostic groups, the prevalence of severe breathlessness increases as death approaches (Table 5). Patients with primary respiratory life-limiting illnesses had the worst breathlessness over the last three months of life, with dypsnea ratings, on average, above 5 out of 10 through this time period. People with primary and secondary lung cancers and heart failure had similar levels of prevalence and intensity. Even in people with no primary cardiorespiratory life-limiting illness, breathlessness prevalence and severity increased significantly as death approached.

Table 4. Median and Mean Levels of Breathlessness by Diagnostic Category for the Whole Population of a Community Palliative Care Service Referred in a Four-Year Period at Three Time Points Before Death (n=5,862)

Characteristics	Maximum Number Evaluated (n)	Days Before Death
		T3a (60–53 days)	T2a (30–23 days)	T1b (7–0 days)
		Mean (SD); Median	Mean (SD); Median	Mean (SD); Median
Overall	5,862	2.0 (2.5); 1.0	2.3 (2.5); 1.6	3.2 (2.7); 6.0
Principle life-limiting illness
Lung cancer—primary	1,081	3.1 (2.6); 3.0	3.6 (2.7); 3.5	4.4 (2.5); 4.5
Lung cancer—secondary	957	2.2 (2.4); 2.0	2.4 (2.5); 2.0	3.4 (2.6); 3.0
Respiratory failure	199	5.0 (3.0); 6.0	5.2 (2.8); 5.5	5.8 (2.8); 6.0
Cardiac failure	265	2.2 (2.3); 1.5	2.4 (2.6); 1.5	2.8 (2.5); 2.3
No primary cardiorespiratory life-limiting illness	3,360	1.4 (2.1); 0.0	1.7 (2.2); 0.5	2.6 (2.4); 2.0

SD=standard deviation.

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• Fig. 3 

  Changes in the mean intensity of breathlessness in five diagnostic groups as death approaches in a consecutive community cohort of people referred to palliative care (n=5,862).

Table 5. Frequencies of “No Breathlessness” and Severe Breathlessness (>7/10) in Major Diagnostic Groups at Three Time Points in a Cohort of 5,862 Patients Followed From Referral to a Community Palliative Care Service Until Death

Sensitivity Analysis 

The direction of findings and magnitude of differences between groups were maintained whether or not all respondents were included or just those with a breathlessness score greater than 0 at any time between referral to the SCHCS and their death.

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Discussion 

These findings highlight the prevalence, intensity, and progression of breathlessness over time despite symptomatic treatment for people facing a life-limiting illness. The fact that at least one in four people have moderate to severe breathlessness in the months before death despite symptomatic treatment is a cause for great concern, especially in the cohort of people who do not have a cancer diagnosis and have higher sustained levels of breathlessness. Breathlessness levels in this study are of similar magnitude to the rates of moderate and severe breathlessness reported a decade ago in another consecutive community cohort (n=370), where data also were collected prospectively at point of care.⁴

A priori, it was decided to dichotomize the data for some of the analyses between cancer and other causes to reflect the literature to date that has grouped end-stage organ failure together. Looking at the overall pattern, subsequent work should explore the population with end-stage respiratory failure and compare them with all the other groups, given the striking similarities in the development of breathlessness for cancer and heart failure in this cohort (Fig. 3). These differences in the systems that most directly affect respiration have not been noted before, and should be the subject of further work in the future.

A group to note includes patients with a life-limiting illness that did not directly affect their cardiorespiratory systems. A number of these people may have occult involvement (subclinical thromboembolic disease and long-standing obstructive or interstitial lung disease), but it is likely that most of them have breathlessness most closely associated with worsening systemic physical functioning. It is likely that symptoms at the end of life relate to a complex interplay of psychological and physical factors as well as the clustering of symptoms, such as fatigue, dyspnea, and pain. This suggests that there may be numerous targets for treatment.

The current rates of breathlessness, particularly in the last days of life, are higher than some other estimates²², ²³ but support the assertion that inclusion of noncancer diagnoses in the estimates of refractory breathlessness will increase the number of people with this symptom.²⁴ This may reflect that patients with greater needs are, for the most part, those referred to specialist palliative care services²¹, ²⁵ and, as such, the subgroup of all people with noncancer diagnoses referred to palliative care had the most severe symptoms, in this case, breathlessness.

A direct comparison was made in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments between inpatients with advanced non-small cell lung cancer (n=939) and patients with an exacerbation of chronic obstructive lung disease (COLD; n=1008) across five teaching hospitals in prospectively collected data. As with this study, breathlessness was twice as prevalent in people with COLD as those with lung cancer (whether from patient or proxy responses), and the cohort with lung cancer was also significantly younger than those with other causes of breathlessness.¹⁸ Of the subgroup with COLD (n≈50), which included inpatients who died within the first year of the study (n=416), it is of interest to note that the four time windows covering the last six months of life saw similar high levels of dyspnea, with no significant worsening as death approached.²⁶ In contrast, the estimates obtained by pooling data from 44 studies and more than 25,000 patients on the prevalence of symptoms in the palliative (cancer) population found that dyspnea was present in only 35% of patients overall and in 39% in the last one to two weeks of life.²³

The Regional Care of the Dying Study had data from 3,696 interviews with bereaved caregivers that allowed a comparison between people with lung cancer (n=449) and chronic lung disease (n=87). Although sampling deliberately favored inclusion of those with lung cancer, as in the current study, there was a significantly higher symptom burden in people with chronic lung disease than with cancer for “any breathlessness” or for the subgroup with “severe breathlessness”.²⁷ This study also showed that the duration of breathlessness was significantly longer for those with COLD.

Strengths of This Study 

This study contains a large cohort of people from a regional palliative care service with data collected at point of face-to-face clinical contact. This avoids recall bias and ensures that accurate and reliable longitudinal trends can be developed. The tool for measuring breathlessness has been validated in this population and fits within the framework for best-practice measurement of this symptom.²⁰ The study reflects day-to-day practice of a large, well-organized community clinical service and the return on investment that can be achieved by systematic point-of-care data collection. It is only with these volumes of data that dyspnea in the broad diagnostic groups reported in this study can be understood in any detail. As staff become familiar with the measurement tools and can see the importance of measurement in an individual's care, a data repository grows that can help to understand the symptom burdens of whole populations.

Longitudinal data are important to understand the evolution of the breathlessness. Three standardized time points allowed prevalence and severity of breathlessness to be followed across time with sufficient numbers of people at each time point to be clinically meaningful.

Limitations 

The data were not recorded specifically for this analysis, but the results can reflect the spectrum of normal clinical encounters in prospectively collected data. Because the data were collected at the point of clinical care, the time between data points varies widely between individuals. This has not directly affected the analysis undertaken. No data using a standardized measure of functional status were collected by the service at the time covered in this study. This has limited the way that the progression of dyspnea could be correlated over time in a standardized way, given previous descriptions of this relationship.⁴ Pulse oximetry was not routinely collected in this cohort, nor were blood gases.

The choice of measurement tools for a somatopsychic experience, incorporating stimulus, transmission, meaning, and response, is difficult for day-to-day practice where dyspnea will be one of the many symptoms routinely evaluated. Although intensity of breathlessness was measured, interference with function was not captured in this study.²⁸, ²⁹, ³⁰ Furthermore, breathlessness can vary in a 24-hour period and with exertion, neither of which will be captured in a question “How is your breathlessness now?” Capturing widely differing domains³¹, ³² using any of the large number of validated measures²⁰ is not possible in routine point-of-care collection.

The choice of subgroups of the five life-limiting illness clusters was an arbitrary decision based on referral patterns to a specialized palliative care service. This could be looked at in more detail when the data set is bigger in another five years' time.

Palliative care remains referral dependent and, in part, the findings may reflect differences in the rates of referral for people whose primary life-limiting illness is not cancer and also may reflect potential differences in the way symptoms are palliated in different diagnostic groups.³, ⁴, ²¹, ³³ This study does not describe the untreated evolution of breathlessness, but the subgroup that has been referred for specialist palliative care, for which symptom control is a prime focus of patient evaluation and care.⁴ This cohort only includes patients referred to the community program. It may be that patients with the most severe breathlessness may have a higher likelihood of being admitted to hospital and that the data, therefore, underestimated the total burden of breathlessness in the whole end-of-life population.

Implications for Research 

This research will help to inform a prospective study in which physiological as well as subjective, demographic, and clinical factors would follow a cohort of people with advanced life-limiting illness to better document the genesis and evolution of dyspnea. Given the small amount of evidence that suggests a restrictive pattern of breathlessness in people with advanced cachexia and no obvious cardiorespiratory involvement, this current study suggests that a better understanding of the relationship between worsening systemic physical functioning, cachexia, fatigue, and breathlessness needs to be investigated in prospective studies.

This cohort was referred for symptom control, yet many patients still had long-term severe breathlessness. Having improved the therapeutic options for the symptomatic relief of dyspnea in the last 20 years, is current knowledge not being applied in the clinical setting?¹³, ¹⁴, ¹⁵, ³⁴ These data suggest that a pattern of care study that assesses the application of available Level I and II evidence for reducing breathlessness correlated with rates of uncontrolled breathlessness be undertaken.

The other research challenge is to understand the breathlessness levels of patients with the same diagnoses who are not referred to palliative care services. Do such people have less, the same, or greater intensities of breathlessness? Novel methods have sought to establish breathlessness levels across the population of people with life-limiting illnesses,²² but prospective population studies are warranted, especially for people for whom cancer is not the primary life-limiting illness.

With a more mature data set, there is a possibility of further dividing diagnostic groups, which are otherwise largely invisible in the literature. Of special note would be the ability to explore the frequency, intensity, and progression of breathlessness in those with documented restrictive lung disease.

Implications for Practice 

Breathlessness was seen to worsen in this cohort despite reassessment by specialist staff using pharmacological and nonpharmacological evidence-based interventions and support.¹³, ¹⁴, ¹⁵, ³⁴ This study defines how many patients developed or had significant worsening of their breathlessness in the last days of life, and that the reported prevalence and intensity of the symptom had changed little in the last two decades,⁴, ¹⁸, ²⁶ despite some high-level evidence for interventions that may lessen the sensation of breathlessness.¹³, ¹⁴, ¹⁵, ³⁴ What is being done by clinicians across the spectrum of care (general practice, respiratory practice, oncologists, ambulance staff, emergency department staff, palliative care teams) to anticipate these changes in the prevalence and intensity of breathlessness, especially for people with primary lung cancer, as functional status declines?

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Conclusions 

Patients with nonmalignant disease experience a sustained period of symptom burden, whereas those with malignant conditions experience dyspnea with increasing prevalence and intensity as death approaches. This study not only underscores the burden of dyspnea as death approaches but also illustrates the importance of considering the symptom burden in the context of diagnoses.

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