title: Changes in Overall Diet Quality and Subsequent Type 2 Diabetes Risk: Three U.S. Prospective Cohorts.
abstract: Recent public health recommendations emphasize adopting a healthful dietary pattern, but evidence is scarce on whether incremental diet quality changes have an impact on long-term diabetes prevention. We aim to evaluate diet quality changes during a 4-year period and subsequent 4-year type 2 diabetes incidence.
  
  
  
  Participants of prospective cohorts, the Nurses' Health Study (NHS), NHS II, and the Health Professionals Follow-up Study, who were free of diabetes at baseline (n = 124,607), were observed for ≥20 years. Diet quality, reflected by the Alternate Healthy Eating Index (AHEI) score, was assessed every 4 years to calculate changes.
  
  
  
  We documented 9,361 cases of type 2 diabetes during 2,093,416 person-years of follow-up. A >10% decrease in AHEI score over 4 years was associated with a higher subsequent diabetes risk (pooled hazard ratio 1.34 [95% CI 1.23-1.46]) with multiple adjustment, whereas a >10% increase in AHEI score was associated with a lower risk (0.84 [0.78-0.90]). Greater improvement in diet quality was associated with lower diabetes risk across baseline diet quality status (P for trend ≤ 0.001 for low, medium, or high initial diet quality) and baseline BMI (P for trend ≤ 0.01 for BMI <25, 25-29, or 30 kg/m2). Changes in body weight explained 32% (95% CI 24-41) of the association between AHEI changes (per 10% increase) and diabetes risk.
  
  
  
  Improvement in overall diet quality is associated with a lower risk of type 2 diabetes, whereas deterioration in diet quality is associated with a higher risk. The association between diet quality changes and diabetes risk is only partly explained by body weight changes.
authors.affiliation: Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA sylvia.ley@channing.harvard.edu frank.hu@channing.harvard.edu.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.
authors.forename: Sylvia H
authors.initials: SH
authors.lastname: Ley
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: An
authors.initials: A
authors.lastname: Pan
authors.affiliation: Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA.|Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.
authors.forename: JoAnn E
authors.initials: JE
authors.lastname: Manson
authors.affiliation: Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.|Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA.
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.affiliation: Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA.|Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA sylvia.ley@channing.harvard.edu frank.hu@channing.harvard.edu.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.|Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA.
authors.forename: Frank B
authors.initials: FB
authors.lastname: Hu
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000178:diet therapy* / Q000453:epidemiology*; D004032:Diet; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008019:Life Style; D008297:Male; D008875:Middle Aged; D015596:Nutrition Assessment; D011446:Prospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology