Seasonality in flares and months of births of patients with ulcerative colitis in a Chinese population

Effects of temperature, weather, seasons, atmosphere, and climate on the exacerbation of inflammatory bowel diseases: A systematic review and meta-analysis

BACKGROUND

Exacerbation of inflammatory bowel disease (IBD) is common. Identification of the exacerbating factors could facilitate interventions for forecastable environmental factors through adjustment of the patient's daily routine. We assessed the effect of natural environmental factors on the exacerbation of IBD.

METHODS

In this systematic review and meta-analysis, studies published from January 1, 1992 to November 3th, 2022 were searched in the MEDLINE, Embase, CINAHL Complete and Cochrane Library databases. We extracted data related to the impact of environmental variations on IBD exacerbation, and performed a meta-analysis of the individual studies' correlation coefficient χ2 converted into Cramér's V (φc) with 95% confidence intervals (CI).

RESULTS

A total of 7,346 publications were searched, and 20 studies (sample size 248-84,000 cases) were selected. A meta-analysis with seven studies was performed, and the pooled estimate of the correlation (φc) between the seasonal variations and IBD exacerbations among 4806 cases of IBD exacerbation was 0.11 (95% CI 0.07-0.14; I2 = 39%; p = 0.13). When divided into subtypes of IBD, the pooled estimate of φc in ulcerative colitis (six studies, n = 2649) was 0.07 (95% CI 0.03-0.11; I2 = 3%; p = 0.40) and in Crohn's disease (three studies, n = 1597) was 0.12 (95% CI 0.07-0.18; I2 = 18%; p = 0.30).

CONCLUSION

There was a significant correlation between IBD exacerbation and seasonal variations, however, it was difficult to synthesize pooled results of other environmental indicators due to the small number of studies and the various types of reported outcome measures. For clinical implications, additional evidence through well-designed follow-up studies is needed.

PROTOCOL REGISTRATION NUMBER (PROSPERO)

CRD42022304916.

Prenatal and Early Life Exposure to the Danish Mandatory Vitamin D Fortification Policy Might Prevent Inflammatory Bowel Disease Later in Life: A Societal Experiment

This register-based national cohort study of 206,900 individuals investigated whether prenatal exposure to small extra doses of vitamin D from fortified margarine prevented inflammatory bowel disease (IBD) later in life; whether the risk of IBD varied according to month or season of birth; and finally, whether there was an interaction between exposure to extra D vitamin and month or season of birth. Fortification of margarine with vitamin D was mandatory in Denmark from the mid-1930s until 1st June 1985, when it was abolished. Two entire birth cohorts, each including two years, were defined: one exposed and one unexposed to the fortification policy for the entire gestation. All individuals were followed for 30 years from the day of birth for an IBD diagnosis in Danish hospital registers. Logistic regression analyses were used to estimate odds ratios (OR) and 95% confidence intervals (CI). Odds for IBD was lower among those exposed to extra D vitamin compared to those unexposed, OR = 0.87 (95% CI: 0.79; 0.95). No association with month or season of birth was found. However, estimates suggested that particularly children born during autumn may have benefitted from the effect of small extra doses of vitamin D. This is, to our knowledge, the first study to explore if prenatal exposure to vitamin D from fortification influenced the risk of IBD. Our results suggest that prenatal exposure to small amounts of extra vitamin D from food fortification may protect against the development of IBD before 30 years of age.

Insolation and Disease Severity in Paediatric Inflammatory Bowel Disease-A Multi-Centre Cross-Sectional Study

This study was to investigate whether the clinical course of inflammatory bowel disease (IBD) in a Polish paediatric cohort fits a seasonal pattern and depends on insolation. Two hundred and fourteen patients diagnosed with Crohn's disease (CD) and 192 with ulcerative colitis (UC) aged from 3 to 18 years, were recruited in seven centres of similar latitude. The seasons were defined as winter (December-February), spring (March-May), summer (June-August), autumn (September-November). The year was also divided depending on insolation threshold (3.0 kWh/m²/day). Patients diagnosed with IBD when the isolation was >3 kWh/m²/day had poorer nutritional status than those diagnosed while insolation was below threshold (lower standardised BMI at diagnosis (-0.81 ([-1.34]-[-0.03]) vs. -0.52 ([-1.15]-0.15); p = 0.0320) and worst flare (-0.93 ([-1.37]-[-0.05]) vs. -0.66 ([-1.23]-0.17); p = 0.0344), with the need for more frequent biological treatment (45.5% vs. 32.7%, p = 0.0100). Patients diagnosed in winter were significantly younger at diagnosis (11.4 vs. 13.0; p_adj = 0.0180) and first immunosuppressive treatment (11.3 vs. 13.3; p_adj = 0.0109) than those diagnosed in other seasons. CD patients diagnosed in months with higher insolation spent more days in hospital than those diagnosed in months with lower insolation [4.6 (1.8-11.8) vs. 2.9 (1.3-6.2); p = 0.0482]. CD patients diagnosed in summer had significantly more concomitant diseases. In patients with CD, the occurrence of the worst flare was more frequent in autumn. Furthermore, the season of birth was associated with Pediatric Crohn's Disease Activity Index at worst flare and earlier surgery. In conclusion, several clinical parameters are associated with insolation, the season of diagnosis and season of birth in the clinical course of Crohn's disease.

An NF-κB-driven lncRNA orchestrates colitis and circadian clock

We uncover a cycling and NF-κB-driven lncRNA (named Lnc-UC) that epigenetically modifies transcription of circadian clock gene Rev-erbα, thereby linking circadian clock to colitis. Cycling expression of Lnc-UC is generated by the central clock protein Bmal1 via an E-box element. NF-κB activation in experimental colitis transcriptionally drives Lnc-UC through direct binding to two κB sites. Lnc-UC ablation disrupts colonic expressions of clock genes in mice; particularly, Rev-erbα is down-regulated and its diurnal rhythm is blunted. Consistently, Lnc-UC promotes expression of Rev-erbα (a known dual NF-κB/Nlrp3 repressor) to inactivate NF-κB signaling and Nlrp3 inflammasome in macrophages. Furthermore, Lnc-UC ablation sensitizes mice to experimental colitis and abolishes the diurnal rhythmicity in disease severity. Mechanistically, Lnc-UC physically interacts with Cbx1 protein to reduce its gene silencing activity via H3K9me3, thereby enhancing Rev-erbα transcription and expression. In addition, we identify a human Lnc-UC that has potential to promote Rev-erbα expression and restrain inflammations.

Circadian pharmacological effects of berberine on chronic colitis in mice: Role of the clock component Rev-erbα

Berberine, initially isolated from Rhizoma Coptidis (Huanglian in Chinese), is a drug used to treat gastrointestinal disorders such as colitis. Here we uncovered a time-varying berberine effect on chronic colitis in mice, and investigated a potential role of the clock protein Rev-erbα in this timing effect. Berberine activity toward Rev-erbα was determined by luciferase reporter, Gal4-cotransfection assay and target gene expression analyses. Chronic colitis was induced by feeding mice with dextran sulfate sodium in drinking water. Colitis severity and pharmacological effects of berberine were assessed by measuring myeloperoxidase and malondialdehyde activities as well as the levels of inflammatory factors (IL-1β, IL-6, IL-18 and Ccl2). Berberine significantly inhibited Bmal1 (-2000/+100 bp)- and Nlrp3 (-1310/+100 bp)-Luc reporter activities, and dose-dependently decreased cellular expressions of both Bmal1 and Nlrp3. Also, it enhanced the transcriptional repressor activity of Rev-erbα in the Gal4 chimeric assay. These data indicated berberine as a Rev-erbα agonist. As expected, berberine attenuated inflammatory responses in BMDMs (bone marrow-derived macrophages) and in colitis mice. However, the anti-inflammatory effects of berberine were lost in BMDMs derived from Rev-erbα-deficient mice. Furthermore, chronic colitis displayed a diurnal rhythmicity in disease severity and its diurnal pattern was in an opposite phase to that of Rev-erbα expression, supporting a direct control of colitis by Rev-erbα. Moreover, berberine effects on chronic colitis were dosing time-dependent. ZT10 dosing generated a better treatment outcome compared to ZT2. This was because colitis was less severe and Rev-erbα expression was much higher at ZT10 than at ZT2. In conclusion, circadian pharmacological effects of berberine on chronic colitis were mainly contributed by diurnal rhythms of both disease severity and Rev-erbα (as a drug target). The findings may have implications for chronotherapeutic practice on colitis or related diseases.

Seasonal Clock Changes Are Underappreciated Health Risks-Also in IBD?

Today, daylight saving time is observed in nearly 80 countries around the world, including the European Union, the USA, Canada, and Russia. The benefits of daylight saving time in energy management have been questioned since it was first introduced during World War I and the latest research has led to varying results. Meanwhile, adverse effects of seasonal time shifts on human biology have been postulated and the European Union is planning to abandon the biannual clock change completely. Medical studies have revealed a correlation of seasonal time shifts with increased incidences of several diseases including stroke, myocardial infarction, and unipolar depressive episodes. Moreover, studies in mice have provided convincing evidence, that circadian rhythm disruption may be involved in the pathogenesis of inflammatory bowel diseases, mainly by disturbing the intestinal barrier integrity. Here, we present previously unpublished data from a large German cohort indicating a correlation of seasonal clock changes and medical leaves due to ulcerative colitis and Crohn's disease. Furthermore, we discuss the health risks of clock changes and the current attempts on reforming daylight saving time from a medical perspective.

Low Sun Exposure and Vitamin D Deficiency as Risk Factors for Inflammatory Bowel Disease, With a Focus on Childhood Onset

The incidence and prevalence of inflammatory bowel disease (IBD) are increasing worldwide. Some ecological studies show increasing incidence with increasing latitude. Ambient ultraviolet radiation varies inversely with latitude, and sun exposure of the skin is a major source of vitamin D. Vitamin D deficiency is common in patients with IBD. Sun exposure and vitamin D have immune effects that could plausibly reduce, or be protective for, IBD. One quarter of new IBD cases are diagnosed in childhood or adolescence, but most research is for adult-onset IBD. Here, we review the evidence for low sun exposure and/or vitamin D deficiency as risk factors for IBD, focusing where possible on pediatric IBD, where effects of environmental exposures may be clearer. The literature provides some evidence of a latitude gradient of IBD incidence, and evidence for seasonal patterns of timing of birth or disease onset is inconsistent. High prevalence of vitamin D deficiency occurs in people with IBD, but cannot be interpreted as being a causal risk factor. Evidence of vitamin D supplementation affecting disease activity is limited. Further research on predisease sun exposure and well-designed supplementation studies are required to elucidate whether these potentially modifiable exposures are indeed risk factors for IBD.

Academic Stress May Contribute to the Onset of Pediatric Inflammatory Bowel Diseases

It is currently unclear whether seasonality affects the onset of inflammatory bowel diseases (IBDs: Crohn disease and ulcerative colitis) in children. Here, we examined the records of pediatric patients with IBD diagnosed between 2009 and 2015 in a discovery cohort of 169 cases and a validation cohort of 122 subjects, where the month of symptoms onset could be determined. No seasonal patterns could be identified in respect to conception, birth, and disease onset. An annual rhythm of symptomatic onset, however, correlating with academic semesters was identified. IBD symptoms in the discovery cohort presented significantly more (P = 0.0218) during 5 months including the initiation (August, September, January) and the termination of academic semesters (December, May) compared to any other 5 months of the year. This observation was validated in the independent cohort (P < 0.0001). Our findings imply that academic stress may contribute to disease onset in pediatric IBD, which may improve timely diagnosis.

The Impact of Cold Spells on the Incidence of Infectious Gastroenteritis and Relapse Rates of Inflammatory Bowel Disease: A Retrospective Controlled Observational Study

Goals

We aimed to assess the impact of very cold days on inflammatory bowel disease (IBD) flares and infectious gastroenteritis (IG). We defined a cold day using the World Meteorological definition of an ice day, which is a day with a maximum temperature below 0°C.

Background

Recently, we have shown that heat waves increase the risk for IG and IBD flares.

Study

We retrospectively collected data from 738 IBD and 786 IG patients admitted to the University Hospital of Zurich between 2001 and 2005 and from 506 patients with other noninfectious chronic intestinal inflammations as controls. Climate data were received by the Swiss Federal Office for Meteorology and Climatology.

Results

There was no evidence for an increased risk of IBD flares (relative risk, RR = 0.99, 95% confidence interval, CI: 0.72-1.33, p = 0.94) or IG flares (RR = 1.16, 95% CI: 087-1.52, p = 0.30) on very cold days. This negative finding was confirmed in alternative formulations with lagged or cumulative (possibly lagged) effects.

Conclusion

In this retrospective controlled observational study, no evidence for an increase in hospital admissions due to flares of IBD and IG during cold days was observed. This may be attributed to not relevantly altered bacterial growth conditions during cold days compared to heat waves.

Age at onset is associated with the seasonal pattern of onset and exacerbation in inflammatory bowel disease

BACKGROUND

Environmental factors are suggested to affect the pathogenesis of several diseases, including inflammatory bowel disease (IBD). The seasonality of disease onset and exacerbation in IBD, however, are not well established. We herein aimed to clarify the disease seasonality and to investigate the underlying characteristics in IBD patients exhibiting seasonality of the disease course.

METHODS

This was a multicenter observational study comprising 20 institutions (Osaka Gut Forum) in Japan. Data were collected from November 2013 to August 2014 using survey forms for physicians and questionnaires for patients. Multivariate analysis was performed to clarify the independent factors affecting disease seasonality.

RESULTS

A total of 1055 patients, including 298 patients with Crohn's disease (CD) and 757 patients with ulcerative colitis (UC), were enrolled. The proportion of CD patients with disease onset in the summer was significantly larger than that in the other seasons, while UC patients exhibited no seasonality of disease onset. More than half of the IBD patients (51.1%) experienced seasonal exacerbation of IBD, and winter was the most common season for disease exacerbation in both CD and UC patients. Seasonality of disease onset and exacerbation was observed in young-onset patients (≤40 years old), but not in elderly-onset patients. Age at onset was independently associated with the seasonality of both disease onset and exacerbation.

CONCLUSIONS

Seasonality of disease onset and exacerbation was observed especially in young-onset IBD patients. Underlying pathophysiologic triggers for disease initiation and exacerbation may be influenced by age at disease onset.

Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity

Autoimmune diseases (ADs) are a heterogeneous groups of diseases that occur as a results of loss of tolerance to self antigens. While the etiopathogeneis remain obscure, different environmental factors were suggested to have a role in the development of autoimmunity, including infections, low vitamin D levels, UV radiation, and melatonin. Interestingly, such factors possess seasonal variation patterns that could influence disease development, severity and progression. Vitamin D levels which reach a nadir during late winter and early spring is correlated with increased disease activity, clinical severity as well as relapse rates in several disease entities including multiple sclerosis (MS), non-cutaneous flares of systemic lupus erythematosus (SLE), psoriasis, and rheumatoid arthritis (RA). Additionally, immunomodulatory actions of melatonin secretion ameliorate the severity of several ADs including MS and SLE. Melatonin levels are lowest during spring, a finding that correlates with the highest exacerbation rates of MS. Further, melatonin is postulated to be involved in the etiopathogenesis of inflammatory bowel diseases (IBD) through it influence on adhesion molecule and therefore transcription factor expression. Moreover, infections can mount to ADs through pro-inflammatory cytokine release and human antigen mimicry. Seasonal patterns of infectious diseases are correlated with the onset and exacerbation of ADs. During the winter, increased incidence of Epstein-Barr virus (EBV) infectious are associated with MS and SLE flares/onset respectively. In addition, higher Rotavirus infections during the winter precedes type 1 diabetes mellitus onset (T1DM). Moreover, Escherichia coli (E. coli) infection prior to primary biliary cirrhosis (PBC) and T1DM disease onset subsequent to Coxachievirus infections are seen to occur during late summer, a finding that correlate with infectious agents' pattern of seasonality. In this review, the effects of seasonality on the onset, relapses and activity of various ADs were discussed. Consideration of seasonal variation patterns of ADs can possibly provide clues to diseases pathogenesis and lead to development of new approaches in treatment and preventative care.

Associations of seasonal patterns and vitamin D levels with onset and flares of pediatric inflammatory bowel disease

BACKGROUND

As inflammatory bowel disease (IBD) might be associated with environmental factors such as seasonal patterns and low vitamin D levels we aimed to assess their association with IBD onset and flares in a large cohort of children.

METHODS

The records of 623 pediatric onset IBD patients were reviewed retrospectively including age at onset, gender, severity indices, month of first symptom, and vitamin D levels at diagnosis. For a subgroup of patients, data included date of first flare and vitamin D levels during flare and remission.

RESULTS

Median age at diagnosis was 14 years (IQR 11.66-15.58). Disease onset did not vary significantly between either month (P=0.367) or seasons (P=0.460). Vitamin D deficiency at the time of diagnosis was prevalent in 21% of patients with no significant association with month, season or disease's type. Vitamin D deficiency was significantly more prevalent in patients with malnutrition (P<0.001) and was associated with hypoalbuminemia (P=0.02) but did not correlate with low bone mineral density. Analysis of 169 first flares showed that flares were more common in June and less common in April (P=0.016). Mean vitamin D level was significantly lower during flares compared with remission (55.25±19.28 vs. 64.16±26.6, respectively, P=0.012).

CONCLUSIONS

IBD onset in school aged children is not associated with seasonal patterns whereas flares may follow a specific monthly pattern. Disease flares are associated with low vitamin D blood levels. Vitamin D deficiency is associated with malnutrition and hypoalbuminemia.

Impact of Seasons and Festivals on the Onset of Acute Pancreatitis in Shanghai, China

OBJECTIVES

Seasonal variation on acute pancreatitis (AP) has not been investigated in Eastern Asia. The aims of the study were to assess the association of the onset of AP with the occurrence of seasons and Chinese festivals and to investigate trends in AP incidence in Shanghai, China.

METHODS

From January 2009 to December 2014, a total of 1780 patients with AP were considered. The incidence was assessed by different etiology and severity. Monthly disease prevalence was investigated to explore the seasonal variation. The prevalence on weekdays, weekends, and festivals was evaluated to establish any weekly or festival influences in AP.

RESULTS

Acute pancreatitis increased from 30.5 per 100,000 in 2009 to 39.2 in 2014 (5.1% annual increase), with greatest increases in alcoholic (19.8% annually) and severe AP (13.7% annually). Time series analysis indicated that prevalence was significantly higher form February to May (spring) and from September to October (autumn). Acute pancreatitis increased during Chinese festivals, 17% and 28% greater than that observed on weekdays and weekends, respectively. Prevalence was greatest in Chinese Spring Festival week.

CONCLUSIONS

Acute pancreatitis increased in Shanghai and had a seasonal variation, with a higher frequency of events in the spring and autumn. Chinese festivals are associated with a high prevalence of AP.

Seasonal variations in onset and exacerbation of inflammatory bowel diseases in children

BACKGROUND

Studies have suggested that inflammatory bowel diseases (IBD) follow a seasonal pattern with regard to their onset and exacerbations. The aim of this study is to determine if there is any seasonal pattern to the onset and exacerbation of IBD in the pediatric population and if the birth of children diagnosed with IBD follows a seasonal pattern.

METHODS

Patients between the ages of 1 and 21 years and with a diagnosis of IBD established between July 1992 and July 2012 were included. Their onset and exacerbations of IBD (year and season) were recorded. The birth dates of the patients were aggregated to determine whether a seasonal birth pattern existed amongst them.

RESULTS

A total of 170 children were included in this study; 34% of patients had their onset in the fall and 19% of them had their onset in the summer. The total number of documented exacerbations was 358 and the median number of exacerbations was two, with a range of 1-11. IBD exacerbations were generally uniformly distributed throughout the year. We did not observe any specific season where children with IBD tended to be born.

CONCLUSIONS

Our data suggests that the onset of symptoms of IBD tends to have a seasonal trend with the highest incidence in the fall. However, we did not observe any association between seasonality and exacerbations in the pediatric population. Moreover, there was no specific season in which children with IBD tended to be born in greater numbers.

Seasonal Variation in Flares of Intestinal Behçet's Disease

BACKGROUND

There have been numerous investigations into the seasonality of several autoimmune diseases and inflammatory bowel disease in an effort to better understand the epidemiology and pathogenesis of these conditions. However, the relationship between the season and disease activity of intestinal Behçet's disease has not been investigated.

AIMS

This study aimed to evaluate the seasonal pattern of exacerbations of intestinal Behçet's disease.

METHODS

We evaluated 268 consecutive patients with intestinal Behçet's disease who were diagnosed and treated between November 1990 and March 2010 at Severance Hospital, Yonsei University, Seoul, Korea. Patient demographics, onset of symptoms, total number of relapses, and the month of each relapse were recorded. The relationship between the season and flares of intestinal Behçet's disease was analyzed.

RESULTS

A total of 339 relapses occurred in 142 patients (53 %). The median age at diagnosis was 39 (10-73) years; the median follow-up duration was 74 (7-372) months. The peak seasons for relapse were spring and autumn, especially the months of May and September (p value <0.001). Compared with winter, spring and autumn had higher rates of flares (HR 1.92 and 1.91, respectively, p value <0.001).

CONCLUSIONS

In this study, intestinal Behçet's disease demonstrated a biphasic pattern (peaks in spring and autumn) in exacerbations of disease, suggesting that seasonal or exogenous factors may be involved in the flares of intestinal Behçet's disease.

Seasonality and pediatric inflammatory bowel disease

OBJECTIVES

Seasonal and geographic variations of inflammatory bowel disease (IBD) exacerbations have been described in adults, with inconsistent findings. We sought to determine whether disease activity in pediatric-onset IBD is associated with a seasonal pattern.

METHODS

We examined children with Crohn disease (CD) and ulcerative colitis (UC) using data from the ImproveCareNow Collaborative between December 2008 and November 2010. We compared the proportion of patients in continuous remission for all recorded visits in each season. We also compared the distribution of all recorded visits with a physician global assessment (PGA) of remission or active disease across seasons.

RESULTS

A total of 1325 patients with CD (6102 visits) and 587 patients with UC (2394 visits) were included. The proportion of patients with UC in continuous remission during each season was highest in the summer (67%) and lowest in the winter (55%) (P=0.01). A similar pattern was found for CD but was not significant. Similarly, the proportion of visits in remission was highest in the summer and lowest in the winter for both UC (29%, 21%; P<0.001) and CD (28%, 23%; P<0.001); however, the distribution of visits with active disease was not significantly different across seasons.

CONCLUSIONS

The higher proportion of patients with UC in continuous remission in the summer may be related to the higher proportion of remission visits in the summer, because the proportion of visits with active disease was similar across seasons. These findings do not support any strong associations between season of the year and disease activity in pediatric IBD.

Linking vitamin d deficiency to inflammatory bowel disease

Inflammatory bowel disease is associated with industrialization, and its incidence has increased markedly over time. The prospect of reversing these trends motivates the search for the agent(s) involved. Modernity entails several physical and behavioral modifications that compromise both the photosynthesis of cholecalciferol in the skin and of its bioavailability. Although deficiency in this "vitamin" has therefore emerged as a leading candidate, and despite the publication of a randomized control trial that showed a trend toward statistically significant benefit in Crohn's disease, its causal agency has yet to be demonstrated by an adequately powered study. We discuss the strengths and weaknesses of the case being made by epidemiologists, geneticists, clinicians, and basic researchers, and consolidate their findings into a model that provides mechanistic plausibility to the claim. Specifically, converging data sets suggest that local activation of vitamin D coordinates the activity of the innate and adaptive arms of immunity, and of the intestinal epithelium, in a manner that promotes barrier integrity, facilitates the clearance of translocated flora, and diverts CD4 T cell development away from inflammatory phenotypes. Because smoking is an important risk-altering exposure, we also discuss its newly established melanizing effect and other emerging evidence linking tobacco use to immune function through vitamin D pathways.

Heat waves, incidence of infectious gastroenteritis, and relapse rates of inflammatory bowel disease: a retrospective controlled observational study

OBJECTIVES

The objective of this study was to evaluate the effect of heat waves on flares of inflammatory bowel disease (IBD) and infectious gastroenteritis (IG).

METHODS

In this retrospective controlled observational study, data from 738 IBD and 786 IG patients admitted to the University Hospital of Zurich in the years 2001-2005, as well as from 506 other noninfectious chronic intestinal inflammations, which were used as control, were collected. Climate data were obtained from the Swiss Federal Office for Meteorology and Climatology.

RESULTS

The presence of a heat wave increased the risk of IBD flares by 4.6% (95% confidence interval (CI): 1.6-7.4%, P=0.0035) and of IG flares by 4.7% (95% CI: 1.8-7.4%, P=0.0020) for every additional day within a heat wave period. In the control group there was no significant effect (95% CI: -6.2-2.9%, P=0.53). Screening of alternative forms for the effect of heat waves suggested that for IG the effect is strongest when lagged by 7 days (risk increase per day: 7.2%, 95% CI: 4.6-9.7%, P<0.0001), whereas for IBD no such transformation was required. Other formulations with additive effects, interactions between heat waves and time of the year, and additional adjustments for daily average temperature did not show any improvement in model fit.

CONCLUSIONS

In this retrospective controlled observational study, we found a substantial increase in hospital admissions because of flares of IBD and IG during heat wave periods. Whereas the effect on IG is strongest with a delay of 7 days, the effect on IBD flares is immediate, suggesting different mechanisms.

Seasonal variation in months of birth and symptom flares in Korean patients with inflammatory bowel disease

Background/Aims

Seasonal variation may influence the development and exacerbation of inflammatory bowel disease (IBD). However, most epidemiologic studies on this topic have been conducted in Western countries. The purpose of this study was to determine whether birth dates and symptom flares follow a seasonal pattern in Korean patients with IBD.

Methods

Patients with a diagnosis of IBD established between January 2003 and December 2010 were investigated at six university hospitals in Korea. The expected births and flares, with a uniform distribution during the year and considering differences in the number of days in the months of 1 year, were calculated.

Results

A total of 411 patients with ulcerative colitis (UC) and 316 patients with Crohn disease (CD) were included in the study. Birth during the winter period, and especially in January and February, was associated with an increased risk of IBD, especially in UC patients. The symptom flares of CD patients occurred most frequently in the spring, with a nadir in the autumn. However, no disease flare seasonality was noted for UC patients.

Conclusions

Our data suggest that seasonally varying environmental factors during pregnancy and the postpartum period are associated with a susceptibility to IBD later in life and that exacerbations of CD are influenced by seasonal factors.

Month of birth, vitamin D and risk of immune-mediated disease: a case control study

BACKGROUND

A season of birth effect in immune-mediated diseases (ID) such as multiple sclerosis and type 1 diabetes has been consistently reported. We aimed to investigate whether season of birth influences the risk of rheumatoid arthritis, Crohn's disease, ulcerative colitis and systemic lupus erythematosus in addition to multiple sclerosis, and to explore the correlation between the risk of ID and predicted ultraviolet B (UVB) light exposure and vitamin D status during gestation.

METHODS

The monthly distribution of births of patients with ID from the UK (n = 115,172) was compared to that of the general population using the Cosinor test. Predicted UVB radiation and vitamin D status in different time windows during pregnancy were calculated for each month of birth and correlated with risk of ID using the Spearman's correlation coefficient.

RESULTS

The distributions of ID births significantly differed from that of the general population (P = 5e-12) with a peak in April (odds ratio = 1.045, 95% confidence interval = 1.024, 1.067, P < 0.0001) and a trough in October (odds ratio = 0.945, 95% confidence interval = 0.925, 0.966, P < 0.0001). Stratification by disease subtype showed seasonality in all ID but Crohn's disease. The risk of ID was inversely correlated with predicted second trimester UVB exposure (Spearman's rho = -0.49, P = 0.00005) and third trimester vitamin D status (Spearman's rho = -0.44, P = 0.0003).

CONCLUSIONS

The risk of different ID in the UK is significantly influenced by the season of birth, suggesting the presence of a shared seasonal risk factor or factors predisposing to ID. Gestational UVB and vitamin D exposure may be implicated in the aetiology of ID.

Influence of photoperiod on hormones, behavior, and immune function

Photoperiodism is the ability of plants and animals to measure environmental day length to ascertain time of year. Central to the evolution of photoperiodism in animals is the adaptive distribution of energetically challenging activities across the year to optimize reproductive fitness while balancing the energetic tradeoffs necessary for seasonally-appropriate survival strategies. The ability to accurately predict future events requires endogenous mechanisms to permit physiological anticipation of annual conditions. Day length provides a virtually noise free environmental signal to monitor and accurately predict time of the year. In mammals, melatonin provides the hormonal signal transducing day length. Duration of pineal melatonin is inversely related to day length and its secretion drives enduring changes in many physiological systems, including the HPA, HPG, and brain-gut axes, the autonomic nervous system, and the immune system. Thus, melatonin is the fulcrum mediating redistribution of energetic investment among physiological processes to maximize fitness and survival.

Environmental risk factors in inflammatory bowel diseases. Investigating the hygiene hypothesis: a Spanish case-control study

OBJECTIVE

Environmental factors have been implicated in the etiology of inflammatory bowel disease (IBD), but evidence for the hygiene hypothesis is unclear. We investigated the relationship between early-life infection-related exposures and risk of IBD.

PATIENTS AND METHODS

A hospital-based case-control study was carried out. A total of 124 cases of Crohn's disease (CD) and 146 of ulcerative colitis (UC) were compared with 235 and 278 well-matched control subjects, respectively. A multi-item questionnaire on familial history of IBD, childhood circumstances and familial socioeconomic status was carried out.

RESULTS

In a multivariate model, living in urban areas (odds ratio (OR) 4.58 (95% CI 2.17-10)), high educational level (OR 1.83 (95% CI 14-2.95)) and social status (OR 1.68 (95% CI 1.2-2.35)) were risk factors for CD, whereas childhood respiratory infections (OR 0.35 (95% CI 0.23-0.52)) and gastroenteritis (OR 0.55 (95% CI 0.36-0.85)) were protective factors. Living in urban areas (OR 4.6 (95% CI 2.29-9.9)), a high educational level (OR 10.3 (95% CI 2.54-42.1)) and social status (OR 2.042 (95% CI 1.31-3.17)) were also risk factors for UC, whereas respiratory infections (OR 0.42 (95% CI 0.29-0.6)) and gastroenteritis (OR: 0.6 (95% CI 0.42-0.86)) were protective factors. Appendectomy (OR 0.173 (95% CI 0.06-0.52)) and current smoking (OR 0.75 (95% CI 0.59-0.96)) were also protective for UC.

CONCLUSION

These results further support the hypothesis that better living conditions during childhood are associated with an increased risk for IBD, and reinforce the negative association between smoking and appendectomy and the risk of UC.