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Methods and Limitations

Methodology

We described blood pressure levels among adults with diabetes using data from the National Health and Nutrition Examination Survey (NHANES). The NHANES is a nationally representative survey conducted by the  National Centers for Health Statistics, Centers for Disease Control and Prevention. NHANES program began in the early 1960s as a series of surveys. Since 1999, the survey became a con­tinuous program. It collects information on the health and nutrition of the U.S. noninstitutionalized civilian population. Participants were interviewed at home, and subsequently received a medical and laboratory examination in a mobile examination center. Survey instruments and physical examination and laboratory measurements are described elsewhere [http://www.cdc.gov/nchs/about/major/nhanes/datalink.htm].

Our study included adults aged 20 years or older with diagnosed diabetes with both valid systolic blood pressure (SBP) and diastolic blood pressure (DBP) measurements. Individuals were classified as having diagnosed diabetes based on the question of whether, other than during pregnancy, a doctor or health care professional had ever told them that they have diabetes. Blood pressure (BP) was measured by trained physicians using mercury sphygmomanometers and appropriate sized arm cuffs. Similar methods were used in NHANES 1988–1994 and NHANES 1999–2006.We used an average of up to three BP readings to determine an individual’s BP level. DBP readings of 0 were treated as missing. Percentages were age-adjusted using the 2000 U.S. standard population of age group 20–44 years, 45–64 years, and 65 years or older. Data preparations were conducted using SAS 9.1.3 (SAS institute, Inc., Cary, North Carolina) and statistical analyses were performed using SUDAAN 9.0 (Research Triangle Institute, Research Triangle Park, North Carolina) to account for complex sample design of NHANES. We used t-tests to assess differences in means and rates between time periods or between subgroups. P-value <0.05 was considered statistically significant.

Limitations

Persons residing in nursing homes or other institutions are not included in this survey. Therefore, these results cannot be generalized to those segments of the population. Due to small sample size, our analyses were limited in statistical power to detect changes in blood pressure levels for some groups. Blood pressure measurement errors may exist since blood pressure was measured at a single occasion in the NHANES. However, the methods were consistent across all NHANES surveys and BP levels were based on average of up to three readings.

BP measurement errors may exist since BP was measured at a single occasion in the NHANES. However, the methods were consistent across all NHANES surveys and BP levels were based on average of up to three readings.

 

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