Models for the spread of universally fatal diseases

In the formulation of models of S-I-R type for the spread of communicable diseases it is necessary to distinguish between diseases with recovery with full immunity and diseases with permanent removal by death. We consider models which include nonlinear population dynamics with permanent removal. The principal result is that the stability of endemic equilibrium may depend on the population dynamics and on the distribution of infective periods; sustained oscillations are possible in some cases.     

Preventing fatal diseases increases healthcare costs: cause elimination life table approach.

OBJECTIVES: To examine whether elimination of fatal diseases will increase healthcare costs. DESIGN: Mortality data from vital statistics combined with healthcare spending in a cause elimination life table. Costs were allocated to specific diseases through the various healthcare registers. SETTING AND SUBJECTS: The population of the Netherlands, 1988. MAIN OUTCOME MEASURES: Healthcare costs of a synthetic life table cohort, expressed as life time expected costs. RESULTS: The life time expected healthcare costs for 1988 in the Netherlands were 56,600 Pounds for men and 80,900 Pounds for women. Elimination of fatal diseases--such as coronary heart disease, cancer, or chronic obstructive lung disease--increases healthcare costs. Major savings will be achieved only by elimination of non-fatal disease--such as musculoskeletal diseases and mental disorders. CONCLUSION: The aim of prevention is to spare people from avoidable misery and death not to save money on the healthcare system. In countries with low mortality, elimination of fatal diseases by successful prevention increases healthcare spending because of the medical expenses during added life years.     

Epidemic and demographic interaction in the spread of potentially fatal diseases in growing populations.

The spread of a potentially fatal infectious disease is considered in a host population that would increase exponentially in the absence of the disease. Taking into account how the effective contact rate C(N) depends on the population size N, the model demonstrates that demographic and epidemiological conclusions depend crucially on the properties of the contact function C. Conditions are given for the following scenarios to occur: (i) the disease spreads at a lower rate than the populations grows and does not modify the population growth rate: (ii) the disease initially spreads at a faster rate than the population grows and lowers the population growth rate in the long run and the following three subscenarios are possible: (iia) the population still grows exponentially, but at a slower rate; (iib) population growth is limited, but the population size does not decay; (iic) population increase is converted into population decrease.     

A geometric approach to comparing treatments for rapidly fatal diseases

In therapy of rapidly fatal diseases, early treatment efficacy often is characterized by an event, "response," which is observed relatively quickly. Since the risk of death decreases at the time of response, it is desirable not only to achieve a response, but to do so as rapidly as possible. We propose a Bayesian method for comparing treatments in this setting based on a competing risks model for response and death without response. Treatment effect is characterized by a two-dimensional parameter consisting of the probability of response within a specified time and the mean time to response. Several target parameter pairs are elicited from the physician so that, for a reference covariate vector, all elicited pairs embody the same improvement in treatment efficacy compared to a fixed standard. A curve is fit to the elicited pairs and used to determine a two-dimensional parameter set in which a new treatment is considered superior to the standard. Posterior probabilities of this set are used to construct rules for the treatment comparison and safety monitoring. The method is illustrated by a randomized trial comparing two cord blood transplantation methods.     

Oral contraceptives and fatal subarachnoid haemorrhage.

A case-control study was conducted of the deaths from subarachnoid haemorrhage (SAH) in women aged 15-44 in England and Wales in 1976. There was a small excess of oral contraceptive use by the women who died from SAH compared with their generally healthy practice-matched controls; this was not, however, statistically significant. Out of 134 women who died from SAH, 34 had a history of hypertension compared with only six of their controls. Renal disease and pre-eclamptic toxaemia were more commonly associated with hypertension in the dead women than in controls. No change in the annual mortality from SAH has been observed in the past 20 years such as might have been expected if the risks were high. Although current or past use of oral contraceptives may have increased the blood pressure and risk of SAH in a few women, the most important factor in determining this risk was hypertension. SAH should thus probably not be regarded as serious cause for concern in healthy non-hypertensive women using oral contraceptives.