There were 2410 admissions meeting the inclusion criteria over the period. These admissions were attributed to 1172 COPD patients, giving an average of 2.06 admissions per patient. In all 2226 (92.4%) of the admissions were discharged to usual places of residence, 12 (0.5%) were discharged to local authority residential accommodation, while 7 (0.3%) were to local authority-run care homes and 3 (0.1%) were to local authority-run hospices. A total of 147 (6.1%) of the admissions resulted in deaths while 15 (0.7%) were transferred to other NHS hospital care providers. The median LOS was 6 days (95% CI 6 to 6) while the mean was 9.8 days (95% CI 9.1 to 10.5).
Length of stay and sociodemographic variable
shows the variation in LOS by patient sociodemographic variables. Mean age at admission was 70.1 years (95% CI 69.7 to 70.5). The minimum age was 40 and the maximum 100 years. The highest proportion of the admissions (32.7%) was for patients aged between 70 and 79 years while the lowest (17.0%) was for patients aged between 40 and 59 years. There were more admissions for females (52.2%) compared with males. More than half (58.3%) of the admissions were for patients from the most deprived fifth quintile areas.
The LOS was significantly longer for those aged 80+ years compared with those aged 40–59 years. Compared with those aged 40–59 years, those aged 80+ years were 41% less likely to be discharged earlier from the hospital (adjusted HR 0.59; p=<0.0001) while those aged 70–79 years were 31% less likely (adjusted HR 0.69; p=<0.0001). There was no significant difference between the likelihood of earlier discharge for those aged 40–59 years and 60–69 years (adjusted HR 0.90; p=0.1830).
Females had a slightly longer LOS compared with males but the difference was not statistically significant for both the mean and median values. The unadjusted HR showed that females were 15% less likely to be discharged earlier compared to males (unadjusted HR 0.85; p=0.0070). However because the proportional hazard assumption did not hold for gender (p=<0.0001), the multivariate model was stratified by gender. No results for gender were presented for the stratified model because stratified Cox model does not report HRs for stratified variables.
There was a significant association between deprivation status of place of residence and LOS with those in the more deprived areas tending to stay longer on admission. Compared with second IMD quintile areas, those from fifth quintile areas were 35% less likely to be discharged earlier (adjusted HR 0.65; p=0.0010), those from the fourth IMD quintile areas were 43% less likely to be discharged earlier (adjusted HR 0.57; p<0.0001), while those from the third quintile areas were 38% less likely (adjusted HR 0.62 p=0.0010).
LOS variations by temporal and geographical factors
shows the variations in LOS by temporal and geographical variables. The highest number of admissions was recorded in 2007/08 financial year while the lowest was recorded in 2006/2007. There were more admissions during December–March (38.1% of all the admissions) compared to the other two seasons.
Variations in length of stay by temporal and geographical factors
The average distance of the places of residence from the hospital was 2.99 km (95% CI 2.94 to 3.05) with the furthest distance being 6.32 km and nearest 0.32 km. Half of the patients were from within 2.75 km (ie, the median distance) radius of the hospital.
There was a statistically non-significant reduction in LOS over the period of the study from a median of 7 days in 2005/2006 to a median of six in 2009/2010. The corresponding mean LOS figures were 11.5 and 9.3 days, respectively. The adjusted HR showed that patients were 22% more likely to be discharged earlier in 2009/2010 compared with 2005/2006 (adjusted HR 1.22; p=0.0100). Statistically significant increase in the likelihood of earlier discharge was noticed as early as 2006/2007 (adjusted HR 1.20; p
0.0130); however, this increase was not sustained over the rest of the period.
Though the number of admissions showed seasonal variations, the LOS did not. Overall we did not notice statistically significant variations in the likelihood of earlier discharge across the three seasons. There were also no significant variations in the likelihood of earlier discharges based on distance from the hospital.
LOS by health condition and health service factors
shows the variations in LOS by health condition and health service variables. Majority (90.8%) of the patients were registered with Blackpool GPs. Just over 50% of the admissions were attributed to COPD with acute exacerbation, unspecified followed by COPD with acute lower respiratory infection (40.2%). The vast majority of the admissions were managed by general medicine specialty (90%) while 7.1% were managed by accident and emergency specialty. Admissions in patients with Charlson index of 1 were in the majority (75.9%) while those with an index of 3+ were in the minority (7.3%).
Variations in length of stay by factors associated with patient's health condition and health service factors
There were no significant variations in LOS based on GP practice location. However, the causes of admissions were associated with LOS. Compared with admissions attributed to COPD with acute exacerbation, unspecified, admissions attributed to COPD with acute lower respiratory infection were 19% less likely to be discharged earlier (adjusted HR 0.81; p=<0.0001) while there was no statistically significant difference between the likelihood of earlier discharge for admissions due to unspecified causes of exacerbations and admissions attributed to other COPD problems (adjusted HR 0.93; p=0.3570).
Specialty of admission was also significantly associated with LOS with admissions managed by accident and emergency specialty being discharged the earliest. Compared with patients managed by the accident and emergency specialties, those managed by general medical specialties were 33% less likely to be discharged earlier (adjusted HR 0.67; p=0.0020) while those managed by other specialties were 37% less likely to be discharged earlier (adjusted HR 0.63; p=0.0020).
Comorbid conditions in patients were associated with LOS. Those with Charlson index of 1 experienced the shortest LOS while those with Charlson index of 3+ experienced the longest. Compared with patients with index 1, those with index 2 were 13% less likely to be discharged earlier (adjusted HR 0.87; p=0.0390) while those with index 3+ were 19% less likely to be discharged earlier (adjusted HR 0.81; p=0.0080).
We noticed statistically significant association for two of the interaction terms (ie, IMD quintile×season and age group×distance) and presented the results for them only (). We did not observe significant association for the rest.
HRs associated with the interaction terms
In the second IMD quintile areas, admissions during August–November were 94% more likely to be discharged earlier compared with admissions during April–July (adjusted HR 1.94; p=0.0150) but in the fourth and fifth deprivation quintile areas the effects were reversed. In the fourth IMD quintile areas, admissions during August–November were 45% less likely to be discharged earlier compared with admissions during April–July (adjusted HR 0.55; p=0.0380) while in the fifth IMD quintile areas, they were 51% less likely to be discharged earlier compared with admissions during April–July (adjusted HR 0.49; p=0.0120). We did not find significant variations in the likelihood of earlier discharge between admissions in April–July and December–March across the second, fourth and fifth quintiles. There were no statistical significant seasonal variations in the LOS for admissions from the third deprivation quintile areas.
Across all age groups, admissions from the fourth distance quintile areas (ie, within 3.1–4.2 km radius of the hospital) were significantly more likely to be discharged earlier compared with those living within the first quintile distance of the hospital. This effect increases with age with those aged 80+ and living within fourth distance quintile of the hospital being more than two times more likely to be discharged earlier compared with their counterparts living within the first distance quintile of the hospital (adjusted HR 2.25; p=0.0010). The interaction term significantly contributed to the fit of the model (p=0.0055).