Regular primary care lowers hospitalisation risk and mortality in seniors with chronic respiratory diseases.

BACKGROUND: Exacerbations in chronic respiratory diseases (CRDs) are sensitive to seasonal variations in exposure to respiratory infectious agents and allergens and patient factors such as non-adherence. Hence, regular general practitioner (GP) contact is likely to be important in order to recognise symptom escalation early and adjust treatment. OBJECTIVE: To examine the association of regularity of GP visits with all-cause mortality and first CRD hospitalisation overall and within groups of pharmacotherapy level in older CRD patients. DESIGN: A retrospective cohort design using linked hospital, mortality, Medicare and pharmaceutical data for participant, exposure and outcome ascertainment. GP visit pattern was measured during the first 3 years of the observation period. Patients were then followed for a maximum of 11.5 years for ascertainment of hospitalisations and deaths. PARTICIPANTS: We studied 108,455 patients aged >or=65 years with CRD in Western Australia (WA) during 1992-2006. MAIN MEASURES: A GP visit regularity score (range 0-1) was calculated and divided into quintiles. A clinician consensus panel classified levels of pharmacotherapy. Cox proportional hazards models, controlling for multiple factors including GP visit frequency, were used to calculate hazard ratios and confidence intervals. KEY RESULTS: Differences in survival curves and hospital avoidance pattern between the GP visit regularity quintiles were statistically significant (p = 0.0279 and p < 0.0001, respectively). The protective association between GP visit regularity and death appeared to be confined to the highest pharmacotherapy level group (P for interaction = 0.0001). Higher GP visit regularity protected against first CRD hospitalisation compared with the least regular quintile regardless of pharmacotherapy level (medium regular: HR = 0.84, 95% CI = 0.77-0.92; 2nd most regular: HR = 0.74, 95% CI = 0.67-0.82; most regular HR = 0.77, 95% CI = 0.68-0.86). CONCLUSIONS: The findings indicate that regular and proactive 'maintenance' primary care, as distinct from 'reactive' care, is beneficial to older CRD patients by reducing their risks of hospitalisation and death.

Uncovering the potential risk of serotonin toxicity in Australian veterans using pharmaceutical claims data.

AIMS: We examined potential risk of serotonin toxicity in Australian veterans by quantifying the concomitant use of serotonergic medicine combinations from claims data collected by the Department of Veterans' Affairs (DVA). METHODS: This was a retrospective cohort study of 273 228 Australian veterans, war widows, widowers and dependents aged >or=55 years and holding full treatment entitlement for the period July 2000 to June 2004 or until death. The main outcome measure was potential concomitant use, estimated as the number of cohort members with an overlap in days of supply for serotonergic medicine combinations over the 4 year period for all medicine combinations and potentially life threatening combinations. RESULTS: From July 2000 to June 2004, 115 969 (42%) cohort members were dispensed at least one serotonergic medicine. 20 658 (8%) had at least one episode of potential concomitant use. We identified 1811 (0.7%) cohort members with at least one overlapping period of potentially life-threatening serotonergic medicine combinations, 937 of whom had the combinations dispensed within the recommended washout period. Three hundred and seventeen of these individuals were dispensed potentially life-threatening medicine combinations on the same day. The most common combinations were moclobemide with a selective serotonin reuptake inhibitor or tramadol. CONCLUSIONS: The individuals potentially at risk of mild to moderate serotonin toxicity were considerable and potentially life threatening combinations were not infrequent. While we were unable to determine how many individuals experienced serotonin toxicity this study indicates, for the first time, the potential size of the problem in a subgroup of elderly Australians. Clinicians and patients need to be vigilant regarding inadvertent concomitant use, especially that of moclobemide with a selective serotonin reuptake inhibitor or tramadol.

Air travel and the risk of deep vein thrombosis.

BACKGROUND: The magnitude of the risk of venous thromboembolism (VTE) following air travel has been difficult to resolve due to a lack of adequate data. We determine the association more precisely by using a large dataset and an improved method of analysis. METHOD: Data on air-travel history for each of 5,196 patients hospitalised for VTE in Western Australia from 1981 to 1999 is analysed using a log-linear regression model for the probability that a flight triggers VTE and for the baseline hazard rate for VTE hospitalisation. RESULTS: The risk of VTE being triggered on the day of an international flight relative to a flight-free day is 29.8 (95% CI 22.4-37.3). Evidence that this relative risk depends on age is weak (p = 0.06), but the absolute risk clearly depends on age. The annual relative risk for an individual taking one international flight, compared with an individual of the same age taking no flight, is estimated to be 1.079. The estimated median time from flight to hospital admission is 4.7 days (95% CI 3.8-5.6) and the estimated 95th percentile is 13.3 (95% CI 10.3-16.8). CONCLUSIONS: Evidence for an association between international air travel and VTE hospitalisation is strong and passengers should be advised on ways to minimise risk during long flights. While 29.8 is a large relative risk, it must be remembered that the baseline risk is very small and the relative risk applies only to the unobserved triggering of a deep vein thrombosis episode on the day of travel; the consequent hospitalisation occurs on one of numerous ensuing days.

Analysis of a potential trigger of an acute illness.

Sometimes certain short-term risk exposures are postulated to act as a trigger for the onset of a specific acute illness. When the incidence of the illness is low it is desirable to investigate this possible association using only data on cases detected during a specific observation period. Here we propose an analysis for such a study based on a model expressed in terms of the probability that the exposure triggers the illness and a random delay from a triggered illness until its diagnosis. Both the natural hazard rate for the illness and the probability that the exposure triggers the illness are assumed to be small and possibly dependent on age and covariates such as sex and duration or severity of the exposure. The method of analysis is illustrated with a study of the association between long flights and hospitalization for venous thromboembolism.

The effect of transient exposures on the risk of an acute illness with low hazard rate.

There are many situations where intermittent short-term exposures of a certain kind are thought to temporarily enhance the risk of onset of an adverse health event (illness). When the hazard rate of the illness is small it is desirable to investigate this possible association using only data on cases occurring in a finite observation period. Here we extend a method for such an analysis by allowing the baseline hazard for the illness to depend on the increasing age over the observation period and using age at the times of exposure, a time dependent variable, as a covariate in the effect of the transient exposure. The method is illustrated with a study of the possible association of long-haul air travel and hospitalization for venous thromboembolism over an observation period of 19 years. It is demonstrated that allowing for aging over the observation period can avoid bias in the estimated effect size when the baseline hazard for the illness increases with age and exposures occur irregularly over time.