Trends in coronary risk factors and electrocardiogram findings from 1977 to 2009 with 10-year mortality in Japanese elderly males - The Tanushimaru Study

A J-shaped Relationship between Sleep Duration and the Risk of Insulin Resistance in a General Japanese Population

Objective Data on the role of sleep in the risk of insulin resistance (IR) are lacking. We therefore examined the association between sleep duration and IR in a general Japanese population. Methods Data of 1,344 individuals 34 to 89 years old from the Tanushimaru Study were analysed. IR was calculated using the fasting plasma glucose level×fasting insulin level/405, i.e. the homeostasis model assessment of IR (HOMA-IR). IR was defined as a HOMA-IR ≥1.73 based on the diagnostic criteria used in Japan. Information regarding sleep duration was collected via questionnaire. Results The frequencies of IR and metabolic syndrome (MetS) were 36.7% and 26.9%, respectively. A J-shaped relationship between sleep duration and IR was observed, and the same relationship was also shown between sleep duration and MetS; however, the relationship with MetS disappeared after adjusting for age, sex, and other confounding factors. Conclusion A J-shaped relationship was observed between sleep duration and the risks of IR in a general Japanese population.

Dietary Transitions and Health Outcomes in Four Populations - Systematic Review

IMPORTANCE

Non-communicable chronic diseases (NCDs) such as obesity, type 2 diabetes, heart disease, and cancer were rare among non-western populations with traditional diets and lifestyles. As populations transitioned toward industrialized diets and lifestyles, NCDs developed.

OBJECTIVE

We performed a systematic literature review to examine the effects of diet and lifestyle transitions on NCDs.

EVIDENCE REVIEW

We identified 22 populations that underwent a nutrition transition, eleven of which had sufficient data. Of these, we chose four populations with diverse geographies, diets and lifestyles who underwent a dietary and lifestyle transition and explored the relationship between dietary changes and health outcomes. We excluded populations with features overlapping with selected populations or with complicating factors such as inadequate data, subgroups, and different study methodologies over different periods. The selected populations were Yemenite Jews, Tokelauans, Tanushimaru Japanese, and Maasai. We also review transition data from seven excluded populations (Pima, Navajo, Aboriginal Australians, South African Natal Indians and Zulu speakers, Inuit, and Hadza) to assess for bias.

FINDINGS

The three groups that replaced saturated fats (SFA) from animal (Yemenite Jews, Maasai) or plants (Tokelau) with refined carbohydrates had negative health outcomes (e.g., increased obesity, diabetes, heart disease). Yemenites reduced SFA consumption by >40% post-transition but men's BMI increased 19% and diabetes increased ~40-fold. Tokelauans reduced fat, dramatically reduced SFA, and increased sugar intake: obesity and diabetes rose. The Tanushimaruans transitioned to more fats and less carbohydrates and used more anti-hypertensive medications; stroke and breast cancer declined while heart disease was stable. The Maasai transitioned to lower fat, SFA and higher carbohydrates and had increased BMI and diabetes. Similar patterns were observed in the seven other populations.

CONCLUSION

The nutrient category most strongly associated with negative health outcomes - especially obesity and diabetes - was sugar (increased 600-650% in Yemenite Jews and Tokelauans) and refined carbohydrates (among Maasai, total carbohydrates increased 39% in men and 362% in women), while increased calories was less strongly associated with these disorders. Across 11 populations, NCDs were associated with increased refined carbohydrates more than increased calories, reduced activity or other factors, but cannot be attributed to SFA or total fat consumption.