Short and long sleep durations are emerging as important behavioral risk factors for mortality. Meta-analyses^1-6 of prospective studies indicate that both short and long sleep durations are associated with all-cause mortality. Despite the strong evidence from meta-analyses, there are a number of limitations to consider⁷: the individual studies included in meta-analyses differ in their follow-up times and selection of confounders and apply heterogenous definitions of what constitutes short and long sleep durations. In addition, the association between long sleep duration and mortality appears stronger in East Asian populations than in North American or European populations.¹

To contribute to evidence-based policy decision making for national cancer control, we conducted a systematic assessment to estimate the current burden of cancer attributable to known preventable risk factors in Japan in 2005. We first estimated the population attributable fractions (PAFs) of each cancer attributable to known risk factors from relative risks derived primarily from Japanese pooled analyses and large-scale cohort studies and the prevalence of exposure in the period around 1990. Using nationwide vital statistics records and incidence estimates, we then estimated the attributable cancer incidence and mortality in 2005. In 2005, ∼55% of cancer among men was attributable to preventable risk factors in Japan. The corresponding figure was lower among women, but preventable risk factors still accounted for nearly 30% of cancer. In men, tobacco smoking had the highest PAF (30% for incidence and 35% for mortality, respectively) followed by infectious agents (23% and 23%). In women, in contrast, infectious agents had the highest PAF (18% and 19% for incidence and mortality, respectively) followed by tobacco smoking (6% and 8%). In Japan, tobacco smoking and infections are major causes of cancer. Further control of these factors will contribute to substantial reductions in cancer incidence and mortality in Japan.

The impact of metabolic factors, which are major risk factors for cardiovascular disease, on total cancer risk has not been clarified. We prospectively examined whether metabolic factors and their aggregates predict the subsequent occurrence of total and major sites of cancer in the Japan Public Health Center-based Prospective Study. A total of 27 724 participants (9548 men and 18 176 women) aged 40-69 years participating in a questionnaire and health checkup survey in 1993-1995 were followed for total cancer incidence through 2004. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for metabolic factors and for two criteria of their aggregates (three or more than three factors and two or more than two additional factors in addition to being overweight) with a Cox proportional hazards model to control for potential confounding factors. In both sexes, the presence of metabolic factors in the aggregate did not predict subsequent occurrence of cancer as a whole. By site, a significant increase in risk was observed for male liver cancer [HR = 1.73, CI = 1.03-2.91 (three or more than three factors); HR = 1.99, CI = 1.11-3.58 (two or more than two additional factors in addition to being overweight)], and female pancreatic cancer [HR = 1.99, CI = 1.00-3.96 (two or more than two additional factors in addition to being overweight)]. For other sites, positive associations were observed only for specific metabolic factors, that is, high triglycerides and male colon cancer (HR = 1.71, CI = 1.11-2.62), and obesity and female breast cancer (HR = 1.75, CI = 1.21-2.55). Metabolic factors in the aggregate may have little impact on total cancer risk in the Japanese population, although the association between specific components and specific cancers suggests an etiologic link between them.

Aims/Introduction: To provide age‐ and sex‐specific trends, age‐standardized trends, and projections of diabetes prevalence through the year 2030 in the Japanese adult population.Materials and Methods: In the present meta‐regression analysis, we included 161,087 adults from six studies and nine national health surveys carried out between 1988 and 2011 in Japan. We assessed the prevalence of diabetes using a recorded history of diabetes or, for the population of individuals without known diabetes, either a glycated hemoglobin level of ≥6.5% (48 mmol/mol) or the 1999 World Health Organization criteria (i.e., a fasting plasma glucose level of ≥126 mg/dL and/or 2‐h glucose level of ≥200 mg/dL in the 75‐g oral glucose tolerance test).Results: For both sexes, prevalence appeared to remain unchanged over the years in all age categories except for men aged 70 years or older, in whom a significant increase in prevalence with time was observed. Age‐standardized diabetes prevalence estimates based on the Japanese population of the corresponding year showed marked increasing trends: diabetes prevalence was 6.1% among women (95% confidence interval [CI] 5.5–6.7), 9.9% (95% CI 9.2–10.6) among men, and 7.9% (95% CI 7.5–8.4) among the total population in 2010, and was expected to rise by 2030 to 6.7% (95% CI 5.2–9.2), 13.1% (95% CI 10.9–16.7) and 9.8% (95% CI 8.5–12.0), respectively. In contrast, the age‐standardized diabetes prevalence using a fixed population appeared to remain unchanged.Conclusions: This large‐scale meta‐regression analysis shows that a substantial increase in diabetes prevalence is expected in Japan during the next few decades, mainly as a result of the aging of the adult population.