The total sample consisted of 316 patients. Subject attrition occurred over the course of the study, with substantial patient mortality during the 6 months of each study in participants aged 65 and older (n = 76). Chi-square (χ2) analysis indicated no significant difference between age categories (χ2 = 1.31, P=.52). Deaths were confirmed according to death certificates. Analysis of the characteristics of the study sample showed an age range from 65 to 93 (mean 71.8 ± 5.4) (). The sample was divided across age categories with 44.9% of the sample aged 65 to 69, 33.2% aged 70 to 74, and 21.8% aged 75 and older. In addition, the sample was balanced between men (49.7%) and women (48.7%) (does not add to 100% because of missing data). Most subjects were white (76.6%) and had completed eighth grade or greater (90.8%).
Demographic, Biological, Psychological, and Treatment Characteristics of Study Sample (N = 316)*
The sample was also balanced across annual income categories, with 30.7% of the subjects earning $0 to $19,999, 20.6% earning $20,000 to $39,999, and 25.3% earning $40,000 and more. Income was unknown for 23.4% of the sample. Although income was balanced across all categories, only 17.7% were working part time or full time. Most participants (61.7%) reported being married or living with a partner, and 26.9% lived alone. Most subjects had newly diagnosed cancer (87.0%), and the sample was balanced across digestive system (22.2%), thoracic (27.2%), gynecological (23.1%), and genitourinary (27.5%). There was a high prevalence of comorbidities across the study sample, with 48.1% reporting three or more. Treatment for cancer included surgery, chemotherapy, radiation therapy, and hormone therapy, and 52.8% of subjects received a combination of therapies; 54.1% received care provided by APNs after surgery.
Mean Functional Status
The mean functional status score over time was calculated for the study sample ( and ). These results demonstrated that, on average, the sample had better functional status at 3 and 6 months than at baseline. These improvements were expected because baseline measures were generally within 1 to 2 months after surgery. The mean functional status score was 43.6 ± 9.0 at baseline (n = 315, range 24.5–67.5), 53.0 ± 8.8 at 3 months (n = 306, range 25.7–67.5), and 55.2 ± 8.5 at 6 months (n = 269, range 23.6–67.5).
Total Function Scores According to Cancer Site and Age (N = 316)
Figure 1 Mean Medical Outcomes Study 36-item Short-Form Survey physical component summary score 50 ± 10 (possible range 2–76, but extreme scores are unlikely).50 Mean Enforced Social Dependency Scale score 50 ± 10 (possible range 20.2–67.5). (more ...)
At baseline, patients with gynecological cancer aged 75 and older had the lowest mean functional status score (38.8 ± 7.6, n = 22), and those aged 75 and older with thoracic cancer reported the highest mean functional status score (48.2 ± 12.7, n = 17). At 3 months, patients aged 65 to 69 with genitourinary cancer reported the highest mean functional status score (55.3 ± 7.7, n = 45), and patients aged 75 and older with digestive cancer had the lowest mean functional status score (48.3 ± 11.6, n = 22). Patients aged 65 to 69 with digestive cancer had the highest mean functional status score (58.2 ± 5.6, n = 15), and those aged 75 and over with thoracic cancer had the lowest mean functional status score (45.9 ± 12.2, n = 13) at 6 months.
Factors Associated with Functional Status
Factors associated with functional status in older adults after surgery for digestive system, thoracic, gynecological, and genitourinary cancer were then explored while controlling for demographic, biological, psychological, and treatment variables at baseline and longitudinally at 3 and 6 months (). Results from the analysis revealed that chronological age was not significantly associated with functional status over time, although there were statistically significant relationships between functional status, cancer category, time, income, treatment, comorbidities, total number of symptoms, and mental health.
Relationship Between Functional Status and Age, Controlling for Demographic, Biological, Psychological, and Treatment Variables (N = 265)
Time of data collection, cancer category, income, and mental health were significantly related to better average functional status. For time of data collection, the results demonstrated that functional status of subjects was better at 3 months (β = 8.97, 95% confidence interval (CI) = 7.14–10.81, P<.001) and 6 months (β = 10.12, 95% CI = 8.15–12.09, P<.001) than at baseline. Patients with thoracic cancer reported better functional status than those with genitourinary cancers (β = 1.97, 95% CI = 0.38–3.56, P = .01). Subjects who earned $40,000 and more annually had better functional status than those earning less than $20,000 (β = 2.82, 95% CI = 1.06–4.57, P=.002). Those who reported better mental health also reported better functional status (β = 0.84, 95% CI = 0.34–1.34, P=.001).
In contrast, the covariates treatment, comorbidities, and symptoms were significantly related to poorer average functional status. Patients who received a combination of surgery and chemotherapy reported poorer functional status than those who underwent surgery alone (β = −1.61, 95% CI = −3.04 to −0.18, P=.03). For comorbidities, patients who had three or more comorbidities had poorer functional status than those who reported no comorbidities (β = −3.78, 95% CI = −6.20 to −1.36, P=.002). Patients who reported one (β = −2.06, 95% CI = −3.21 to −0.91, P<.001), two (β = −3.95, 95% CI = −5.62 to −2.28, P<.001), and three or more symptoms (β = −6.05, 95% CI = −7.39 to −4.71, P<.001) also reported poorer functional status than those without symptoms.
All of the results were statistically significant if a 10% false discovery rate was assumed. With 316 people and standardized outcome and covariates (all standardized to have the same variance), there would be 80% power to detect a correlation or slope between a covariate and the outcome of 0.16 using a simple linear regression. This assumes the use of two-sided hypothesis tests and 5% Type 1 error rates. A correlation of 0.16 is often considered relatively modest.36
Whether the inferences concerning functional status and demographic, biological, psychological, and treatment variables changed if baseline functional status was included as a covariate in the model was first investigated. Results from this analysis again revealed that chronological age was not significantly associated with functional status over time, although there were statistically significant relationships between functional status and time of data collection, mental health, number of symptoms, and cancer category and stage. Patients reported significantly better functional status at 6 months than at 3 months (β = 1.19, 95% CI = 0.09– 2.38, P=.048). Patients with digestive cancer reported better functional status than those with genitourinary cancer (β = 2.18, 95% CI = 0.07–4.28, P=.04). In addition, patients reporting better mental health reported better functional status (β = 0.72, 95% CI = 0.08–1.37, P=.03). In contrast, patients who reported one (β = −2.58, 95% CI = −3.84 to −1.31, P<.001), two (β = −4.60, 95% CI = −6.43 to −2.78, P<.001), and three or more (β = −5.64, 95% CI = −7.26 to −4.02, P<.001) symptoms also reported poorer functional status than those reporting no symptoms. Patients with late-stage cancers also reported poorer functional status than those with unknown- or early-stage cancers (β = −2.06, 95% CI = −3.72 to −0.41, P=.01).
Next, whether the inferences were different when examining change in functional status from baseline to 3 months and from 3 to 6 months was investigated. Results from this analysis again demonstrated that chronological age was not significantly associated with rate of change in functional status. One factor, unknown income, was positively associated with better rate of change in functional status. Time of data collection, symptoms, and cancer stage were associated with lower rate of change in functional status. Participants reporting unknown income experienced higher rate of change in functional status than those reporting income less than $20,000 (β = 2.13, 95% CI = 0.30–4.0, P=.02). In contrast, the rate of change in functional status was less between 3 and 6 months than between baseline and 3 months (β = −11.19, 95% CI = −13.57 to −8.81, P<.001). Participants who reported one (β = −2.06, 95% CI = −4.13–0.00, P=.050) and three or more symptoms (β = −4.44, 95%CI = −6.23 to −2.66, P<.001) also experienced lower rate of change than those without symptoms. Additionally, study participants with late-stage cancers reported lower rate of change in functional status over time than those with unknown- or early-stage cancers (β = −2.02, 95% CI = −3.36 to −0.68, P=.003).