Background and Aims Although the incidence of inflammatory bowel disease [IBD] is increasing in Asia, data on long-term epidemiological trends are limited. We performed a 30-year longitudinal study to investigate temporal trends in the epidemiology of Crohn’s disease [CD] and ulcerative colitis [UC] in Seoul, Korea. Methods This population-based study included 1431 IBD patients [418 CD, 1013 UC] diagnosed between 1986 and 2015 in the Songpa-Kangdong district of Seoul, Korea. Temporal trends in incidence, prevalence, and disease phenotype at diagnosis were analysed. Results The adjusted mean annual incidence rates of CD and UC per 100 000 inhabitants increased from 0.06 (95% confidence interval [CI], 0.05–0.07) and 0.29 [95% CI, 0.27–0.31], respectively, in 1986–1990 to 2.44 [95% CI, 2.38–2.50] and 5.82 [95% CI, 5.73–5.92], respectively, in 2011–2015. Average annual percentage change in IBD incidence was 12.3% in 1986–1995, 12.3% in 1996–2005, and 3.3% in 2006–2015. The male-to-female ratio of the adjusted incidence rate was 3.3:1 for CD and 1.2:1 for UC. Perianal fistula/abscess was present in 43.3% of patients before or at CD diagnosis. At diagnosis, 54.3% of UC patients presented only with proctitis. The adjusted prevalence rate in 2015 was 31.59/100 000 [95% CI, 31.10–32.07] for CD and 76.66/100 000 [95% CI, 75.91–77.42] for UC. Conclusions The incidence and prevalence of IBD in Korea have continued to increase over the past three decades. Korean patients have distinct demographic and phenotypic characteristics, including a male predominance and high frequency of perianal fistula/abscess in CD and high proportion of proctitis in UC.

ObjectiveNo population-based study has evaluated the natural course of UC over three decades in non-Caucasians. We aimed to assess the long-term natural course of Korean patients with UC in a population-based cohort.DesignThis Korean population-based, Songpa-Kangdong IBD cohort included all patients (n=1013) newly diagnosed with UC during 1986–2015. Disease outcomes and their predictors were evaluated.ResultsDuring the median follow-up of 105 months, the overall use of systemic corticosteroids, thiopurines and antitumour necrosis factor (anti-TNF) agents was 40.8%, 13.9% and 6.5%, respectively. Over time, the cumulative risk of commencing corticosteroids decreased, whereas that of commencing thiopurines and anti-TNF agents increased. During follow-up, 28.7% of 778 patients with proctitis or left-sided colitis at diagnosis experienced proximal disease extension. A total of 28 patients (2.8%) underwent colectomy, demonstrating cumulative risks of colectomy at 1, 5, 10, 20 and 30 years after diagnosis of 1.0%, 1.9%, 2.2%, 5.1% and 6.4%, respectively. Multivariate Cox regression analysis revealed that extensive colitis at diagnosis (HR 8.249, 95% CI 2.394 to 28.430), ever use of corticosteroids (HR 6.437, 95% CI 1.440 to 28.773) and diagnosis in the anti-TNF era (HR 0.224, 95% CI 0.057 to 0.886) were independent predictors of colectomy. The standardised mortality ratio in patients with UC was 0.725 (95% CI 0.508 to 1.004).ConclusionKorean patients with UC may have a better clinical course than Western patients, as indicated by a lower colectomy rate. The overall colectomy rate has continued to decrease over the past three decades.

The convergence behavior of the total and correlation energies of He, H2, and He2 with the increase of basis quality in the correlation-consistent basis sets, cc-pVXZ and aug-cc-pVXZ(X=D,T,Q,5,6), was studied to search for a proper extrapolation scheme to predict the accurate complete basis set (CBS) limits at the MP2, CCSD, and CCSD(T) level. The functional form employed for extrapolation is a simple polynomial including inverse cubic power and higher-order terms of the cardinal number X in the correlation-consistent basis set as well as exponential function. It is found that a simple extrapolation of two successive correlation-consistent basis set energies (total or correlation energies) using (X+k)−3 [k=0 for MP2 and k=−1 for CCSD and CCSD(T) level] gives in general the most reliable (and accurate in case of total energy) estimates to the CBS limit energies. It is also shown that the choice of proper basis set, which can represent the electronic motions in the fragment and complex equally well, appears necessary for reliable estimate of the relative energies such as the binding energy of the complex. From the extrapolation of aug-cc-pV5Z and aug-cc-pV6Z energies with (X+k)−3, we obtained 21.3(21.4), 28.4(29.0) and 33.2(33.8) microhartrees as the CBS limit binding energy of He2 at the internuclear separation of 5.6 a.u. at the MP2, CCSD, and CCSD(T) level, respectively, with the values in parentheses representing the exact CBS limit binding energies.

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The equilibrium and saddle point structures of the ammonia dimer were investigated employing a series of correlation-consistent basis sets, cc-pVXZ and aug-cc-pVXZ(X=D,T,Q) at the Hartree–Fock (HF), second order and fourth order Møller–Plesset perturbation theory (MP2, MP4) levels. It is shown that the energies and geometries of the stationary structures are sensitive to the basis set and electron correlation, and the proper combination of electron correlation treatment (MP2 or better) and basis set requirement (aug-cc-pVTZ or better) is necessary to determine the equilibrium structure and ordering of the stationary structures. The equilibrium structure of the ammonia dimer is found to be an asymmetric cyclic (eclipsed) structure with Cs symmetry. Although this is generally consistent with the equilibrium structure predicted from the model potential by Olthof et al. [J. Chem. Phys. 101, 8430 (1994)], it appears to be more shifted toward the linear structure than the centrosymmetric cyclic structure, which signifies a certain degree of hydrogen bonding in this dimer. The MP2 barrier height to proton donor–acceptor interchange at MP2/aug-cc-pVQZ//MP2/aug-cc-pVTZ is 7.6 cm−1, which is in excellent agreement with the value predicted from the model potential by Olthof et al. While the barrier height to rotation of one monomer (hydrogen-bond acceptor) about its C3 axis is relatively low, ∼20 cm−1, the corresponding value of the other monomer (hydrogen-bond donor) is shown to be rather high, probably more than 450 cm−1 at the equilibrium structure. The binding energies of the ammonia dimer are computed with and without counterpoise correction for basis set superposition error. The MP2 complete basis set (CBS) limit electronic binding energy of (NH3)2 is estimated to be within 13.2±0.3 kJ/mol.