Free-of-charge long-acting reversible contraception : two-year discontinuation, its risk factors, and reasons

BACKGROUND: Since 2013, the residents of the city of Vantaa, Finland, have been offered their first long-acting reversible contraceptive method (levonorgestrel-releasing intrauterine system, implant, and copper intrauterine device) free of charge. OBJECTIVE: The primary aim of this study was to assess the 2-year cumulative discontinuation rates of long-acting reversible contraceptive methods when provided free of charge for first-time users in a real-world setting. Additional aims were to describe factors associated with discontinuation and to evaluate the reasons for discontinuation. STUDY DESIGN: This is a retrospective register-based cohort study of 2026 nonsterilized women aged 15 to 44 years, who initiated a free-of-charge long-acting contraceptive method in 2013-2014 in the city of Vantaa. Removals within 2 years after method initiation and reasons for discontinuation were obtained from electronic health records and from national registers. We calculated the 2-year cumulative incidence rates of discontinuation with 95% confidence intervals for each method. Furthermore, we assessed crude and adjusted incidence rate ratios of discontinuation with 95% confidence interval by Poisson regression models comparing implants and copper intrauterine device with levonorgestrel-releasing intrauterine systems. RESULTS: During the 2 -year follow-up, 514 women discontinued, yielding a cumulative discontinuation rate of 28.3 per 100 women-years (95% confidence interval, 26.2-30.4). Among the 1199 women who initiated the levonorgestrel-releasing intrauterine system, the cumulative discontinuation rate was 24.2 per 100 women-years (95% confidence interval, 21.7-26.9); among the 642 implant users, 33.3 per 100 women-years (95% confidence interval, 29.5-37.4); and among the 185 copper intrauterine device users, 37.8 per 100 women-years (95% confidence interval, 31.0-45.7). Compared with women aged 30 to 44 years, women aged 15 to 19 years (adjusted incidence rate ratio, 1.58; 95% confidence interval, 1.17-2.14) and 20 to 29 years (adjusted incidence rate ratio, 1.35; 95% confidence interval, 1.11-1.63) were more likely to discontinue. We observed a higher discontinuation rate in women who had given birth within the previous year (adjusted incidence rate ratio, 1.36; 95% confidence interval, 1.13-1.65), spoke a native language other than Finnish or Swedish (adjusted incidence rate ratio, 1.31; 95% confidence interval, 1.06-1.63), and had a history of a sexually transmitted infection (adjusted incidence rate ratio, 1.62; 95% confidence interval, 1.07-2.46). No association was found in marital status, overall parity, history of induced abortion, socioeconomic status, education level, or smoking status. The most common reason for discontinuation was bleeding disturbances, reported by 21% of women who discontinued the levonorgestrel-releasing intrauterine system, by 71% who discontinued the implant, and by 41% who discontinued the copper intrauterine device. One in 4 women who discontinued the copper intrauterine device reported heavy menstrual bleeding, whereas only 1% who discontinued the levonorgestrel-releasing intrauterine system and none who discontinued implants reported this reason. Abdominal pain was the reported reason for discontinuation in 20% of both intrauterine device users and in only 2% who discontinued implants. CONCLUSION: At 2 years, the use of implants and copper intrauterine devices was more likely to be discontinued than that of the levonorgestrelreleasing intrauterine system. Women younger than 30 years and those who gave birth in the preceding year, spoke a native language other than Finnish or Swedish, or had a history of sexually transmitted infections were more likely to discontinue. The levonorgestrel-releasing intrauterine system was least likely to be removed owing to bleeding disturbances.YPeer reviewe

Legal protection of plant biotechnological inventions

Within biotechnology, plant production is regarded as one of the most promising adaptations. New plant breeding methods are considered to better fulfil the requirements set on patentability than the traditional breeding methods. In Europe, a plant variety can be protected by special legislation. The present patent laws in Europe are not applied to plant biotechnological inventions. The United States has three systems under which new varieties of plants may be protected. These include The 1930 Plant Patent Act, The 1970 Plant Variety Protection Act and The 1952 Patent Statute. Companies that have specialized in plant breeding and organizations representing the industrial countries recommend improvements to the legal protection. On the other hand, farmers and the developing countries are against better protection

Asymptotic Expansions for Stationary Distributions of Perturbed Semi-Markov Processes

New algorithms for computing of asymptotic expansions for stationary distributions of nonlinearly perturbed semi-Markov processes are presented. The algorithms are based on special techniques of sequential phase space reduction, which can be applied to processes with asymptotically coupled and uncoupled finite phase spaces.Comment: 83 page

Persistence for stochastic difference equations: A mini-review

Understanding under what conditions populations, whether they be plants, animals, or viral particles, persist is an issue of theoretical and practical importance in population biology. Both biotic interactions and environmental fluctuations are key factors that can facilitate or disrupt persistence. One approach to examining the interplay between these deterministic and stochastic forces is the construction and analysis of stochastic difference equations $X_{t+1}=F(X_t,\xi_{t+1})$ where $X_t \in \R^k$ represents the state of the populations and $\xi_1,\xi_2,...$ is a sequence of random variables representing environmental stochasticity. In the analysis of these stochastic models, many theoretical population biologists are interested in whether the models are bounded and persistent. Here, boundedness asserts that asymptotically $X_t$ tends to remain in compact sets. In contrast, persistence requires that $X_t$ tends to be "repelled" by some "extinction set" $S_0\subset \R^k$. Here, results on both of these proprieties are reviewed for single species, multiple species, and structured population models. The results are illustrated with applications to stochastic versions of the Hassell and Ricker single species models, Ricker, Beverton-Holt, lottery models of competition, and lottery models of rock-paper-scissor games. A variety of conjectures and suggestions for future research are presented.Comment: Accepted for publication in the Journal of Difference Equations and Application

A General Inverse Problem for the Growth-Fragmentation Equation

The growth-fragmentation equation arises in many different contexts, ranging from cell division, protein polymerization, biopolymers, neurosciences etc. Direct observation of temporal dynamics being often difficult, it is of main interest to develop theoretical and numerical methods to recover reaction rates and parameters of the equation from indirect observation of the solution. Following the work done in (Perthame, Zubelli, 2006) and (Doumic, Perthame, Zubelli, 2009) for the specific case of the cell division equation, we address here the general question of recovering the fragmentation rate of the equation from the observation of the time-asymptotic solution, when the fragmentation kernel and the growth rates are fully general. We give both theoretical results and numerical methods, and discuss the remaining issues

Structured models of cell migration incorporating molecular binding processes

The dynamic interplay between collective cell movement and the various molecules involved in the accompanying cell signalling mechanisms plays a crucial role in many biological processes including normal tissue development and pathological scenarios such as wound healing and cancer. Information about the various structures embedded within these processes allows a detailed exploration of the binding of molecular species to cell-surface receptors within the evolving cell population. In this paper we establish a general spatio-temporal-structural framework that enables the description of molecular binding to cell membranes coupled with the cell population dynamics. We first provide a general theoretical description for this approach and then illustrate it with two examples arising from cancer invasion

Effect of Cellular Quiescence on the Success of Targeted CML Therapy

Similar to tissue stem cells, primitive tumor cells in chronic myelogenous leukemia have been observed to undergo quiescence; that is, the cells can temporarily stop dividing. Using mathematical models, we investigate the effect of cellular quiescence on the outcome of therapy with targeted small molecule inhibitors.According to the models, the initiation of treatment can result in different patterns of tumor cell decline: a biphasic decline, a one-phase decline, and a reverse biphasic decline. A biphasic decline involves a fast initial phase (which roughly corresponds to the eradication of cycling cells by the drug), followed by a second and slower phase of exponential decline (corresponding to awakening and death of quiescent cells), which helps explain clinical data. We define the time when the switch to the second phase occurs, and identify parameters that determine whether therapy can drive the tumor extinct in a reasonable period of time or not. We further ask how cellular quiescence affects the evolution of drug resistance. We find that it has no effect on the probability that resistant mutants exist before therapy if treatment occurs with a single drug, but that quiescence increases the probability of having resistant mutants if patients are treated with a combination of two or more drugs with different targets. Interestingly, while quiescence prolongs the time until therapy reduces the number of cells to low levels or extinction, the therapy phase is irrelevant for the evolution of drug resistant mutants. If treatment fails as a result of resistance, the mutants will have evolved during the tumor growth phase, before the start of therapy. Thus, prevention of resistance is not promoted by reducing the quiescent cell population during therapy (e.g., by a combination of cell activation and drug-mediated killing).The mathematical models provide insights into the effect of quiescence on the basic kinetics of the response to targeted treatment of CML. They identify determinants of success in the absence of drug resistant mutants, and elucidate how quiescence influences the emergence of drug resistant mutants

Computational Approaches and Analysis for a Spatio-Structural-Temporal Invasive Carcinoma Model

Spatio-temporal models have long been used to describe biological systems of cancer, but it has not been until very recently that increased attention has been paid to structural dynamics of the interaction between cancer populations and the molecular mechanisms associated with local invasion. One system that is of particular interest is that of the urokinase plasminogen activator (uPA) wherein uPA binds uPA receptors on the cancer cell surface, allowing plasminogen to be cleaved into plasmin, which degrades the extracellular matrix and this way leads to enhanced cancer cell migration. In this paper, we develop a novel numerical approach and associated analysis for spatio-structuro-temporal modelling of the uPA system for up to two-spatial and two-structural dimensions. This is accompanied by analytical exploration of the numerical techniques used in simulating this system, with special consideration being given to the proof of stability within numerical regimes encapsulating a central differences approach to approximating numerical gradients. The stability analysis performed here reveals instabilities induced by the coupling of the structural binding and proliferative processes. The numerical results expound how the uPA system aids the tumour in invading the local stroma, whilst the inhibitor to this system may impede this behaviour and encourage a more sporadic pattern of invasion.PostprintPeer reviewe