Table 1 Characteristics of studies included in the meta-analysis

Alehagen 2015,

Sweden

Longitudinal study (data were extracted from baseline)

Community, rural municipality of inhabitants in the south-east of Sweden.

668

47.8

NR

Quartiles: <57.2, 57.2–67.1, 67.1–76.1, >76.1 μg/l

NR

Bleys 2007,

USA

Cross-sectional study

Community, NHANES III participants

8876

49.1

26.9

Quintiles: <111.62, 111.62–120.17, 120.18–128.25, 128.26–137.65, >137.65 μg/l

Defined as a fasting plasma glucose ≥ 126 mg/dl, a self-report of a physician diagnosis of diabetes, or current use of insulin or oral hypoglycemic medication

Laclaustra 2009,

USA

Cross-sectional study

Community, civilian non-institutionalized U.S. population from NHANES 2003–2004

890

47.0

28.8

Quartiles: <124, 124–133, 134–146, >146 μg/l

Defined as the presence of either a self-report of current use of hypoglycemic agents or insulin or fasting plasma glucose ≥ 126 mg/dL.

Stranges 2011,

Italy

Longitudinal study (data were extracted from baseline)

Community, male workforce of the Olivetti factories in Pozzuoli (Naples) and Marcianise (Caserta), Southern Italy.

445

100

26.8

Tertiles: <69.7, 69.7–82.6, > 82.6 μg/l

Defined as a fasting blood glucose level ≥ 126 mg/dL or anti-diabetic therapy.

Gao 2014,

Sweden

Longitudinal Study

Community, all 50-year-old men living in Uppsala County, Sweden.

1925

100

25.0

Tertiles: 61.4, 75.1, 91.1 μg/l^a

Defined by elevated fasting glucose levels and/or use of anti-diabetic medicine. Elevated glucose levels were assessed as fasting blood glucose ≥6.1 mmol/l at the age 60 years’ examination (equals ≥7.0 mmol/l of plasma glucose) and fasting plasma glucose ≥ 7.0 mmol/l at age 70 years and age 77 years