EAL

FNOA: Aging Programs (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the associations of education and income with bone health in non-Hispanic White, non-Hispanic Black and Mexican-American post-menopausal women
To determine if any observed associations can be explained by behavioral factors such as estrogen use, calcium intake, smoking and physical activity
To determine if government food assistance and education are associated with increased calcium intake among low-income women.

Inclusion Criteria:

Post-menopausal women with acceptable DXA scans and complete data for other variables related to the study (including dietary recall)
Post-menopausal was defined as women who:
- Had a hysterectomy or both ovaries removed
- Were aged 40 years and older and had not had a period for 12 months and were not pregnant
- Were aged 70 years or older.

Exclusion Criteria:

Women below the age of 60 who tested positive or uncertain on a pregnancy test
Women below the age of 60 whom could possibly be pregnant
All examinees who had ever broken or fractured both hips or who had hip pins or artificial hips

Description of Study Protocol:

Recruitment: No participants were recruited specifically for this study. The study involved secondary analysis of data gathered in the Third National Health and Nutrition Examination Survery (NHANES III). A cross-sectional representation of the US population was obtained for NHANES and their data was used for this study.
Design: Cross-sectional data were gathered using a stratified multi-stage probability design
Statistical analysis: Multiple linear regression was used to evaluate the associations of education, income and behavioral factors with BMD.

Data Collection Summary:

Timing of Measurements

NHANES III data was collected in two phases between October 1988 and October 1994
Dates of data review and analysis for this study were not specified
Data was gathered from a household interview and physical examination conducted at a mobile examination unit.

Dependent Variables

Bone mineral density for total hip and femoral neck was measured by dual-energy X-ray absorptiometry (DXA) and was separately reviewed by the Mayo Clinic
Height and weight were obtained as part of the NHANES study; methods were not specified for this study.

Independent Variables

Education in years
Income as a ratio relative to the federal Poverty Income Ratio (PIR).

Other Variables

Estrogen use, as measured by use of estrogen-containing contraceptives, estrogen creams, suppositories or injections or female hormone patches
Calcium intake, as determined from a computer-assisted 24-hour recall
Smoking, as determined by interview with participant (number of cigarettes per day)
Physical activity, as determined by interview with participant (categorized as high, moderate or low)
Height and weight (method of measurement not specified)
Years since menopause, as reported by subjects
Participation in the Food Stamp Program and Senior Nutrition Program, as reported by NHANES interview
Acculturation, as defined by variables representing birth place and language
Specific information on the household interview, including questions asked, was not available as part of this study.

Description of Actual Data Sample:

Initial N: 2,905 women who had both complete data and technically acceptable DXA scans were selected from the orignal NHANES sample of 3,855 women. Initial N=2,905.
Attrition (final N): 2,905 women
Age: 40 years or older
Ethnicity: The study used data on white (N=1,351), black, (N=581) and Mexican-American (N=478) women.

Anthropometrics

Non-Hispanic white people had heights of 160.7±0.2cm and weights of 70.8±0.6kg, non-Hispanic black people had heights of 162.4±0.3cm and weights of 79.4±0.9kg and Mexican-Americans had heights of 155.8±0.3cm and weights of 70.3±0.9kg.

Location

This study was based on NHANES data and is a representative sample of the US population.

Summary of Results:

Associations of Education, Income, Acculturation, Estrogen Use, Calcium Intake, Physical Activity and Smoking with Total Hip BMD*

		Non-Hispanic Whites	Non-Hispanic Blacks	Mexican-Americans
		R²=0.43	R²=0.46	R²=0.49
Education (Years)		-0.002±0.002	0.001±0.001	-0.0002±0.002
Income (PIR)		0.003±0.002	0.001±0.005	0.002±0.004
Acculturation		NA	NA
Born in the US and English-Speaking				0.02±0.04
Born in the US and Spanish-Speaking				-0.02±0.01
Born in Mexico				Comparison group
Estrogen Use (Ever vs. Never)		0.03±0.01 P<0.0001	0.01±0.01	0.02±0.01 P=0.09
Calcium Intake		0.02±0.01 P<0.01	0.01±0.02	0.001±0.01
Physical Activity	High	0.03±0.01 (P<0.005)	0.004±0.02	-0.01±0.02
	Moderate	0.02±0.01 (P<0.05)	-0.01±0.01 (P<0.07)	-0.01±0.01
	Low	Comparison group	Comparison group	Comparison group
Smoking (Cigarettes per Day)		-0.001±0.0004 (P<0.001)	-0.001±0.0006 (P=0.06)	-0.002±0.001

* Numbers show statistically significant regression coefficients ±SE for sociodemographic and behavioral variables in bold font with total hip bone mineral density as the outcome variable. Models were adjusted for age, years since last menstrual period, weight and height.

Associations of Participation in Food Assistance Programs, Education and Acculturation with Calcium Intake (mg per dL) in Low-Income Post-Menopausal Women

	Non-Hispanic Whites	Non-Hispanic Blacks	Mexican -Americans
Food Stamps (Yes or No)	74±77	87±43 (P<0.05)	5±79
Education (Years)	32±7 (P<0.001)	15±7(P<0.05)	13±6(P<0.05)
Acculturation	NA	NA
Born in the US and English-Speaking			-184±76 (P<0.05)
Born the the US and Spanish-Speaking			-94±74
Born in Mexico			Comparison group
Senior Nutrition Program (Yes or No)	-46±52	11±5 (P<0.05)	NS
Education (Years)
Acculturation
Born in the US and English-Speaking			-162±55 (P<0.01)
Born in the US and Spanish-Speaking			-139±42 (P<0.01)
Born in Mexico			Comparison group

Numbers show regression coefficients ±SE for variables of interest with calcium as the outcome variable. Statistically significant regression coefficients are shown in bold.

Other Findings

Among black people, education was positively associated with BMD, while among white people, it was income that was associated with BMD. When education and income were combined and used to categorize the women into three groups, the group with low education and low income had lower BMD than the group with more education and a higher income.
Neither education nor income was associated with BMD among Mexican-Americans
Associations with education and income with BMD were reduced considerably and not statistically significant when behavioral factors known to influence BMD (estrogen use, pregnancy history, calcium intake, physical activity and smoking) were considered. BMD was observed to be positively associated with estrogen use (P<0.0001), higher calcium intake (P<0.01) and high physical activity levels (P<0.05) in white women.
Smoking was significantly associated with lower BMD in white women (P<0.001). An association was noted in black women, but it was not statistically significant.
Education was associated with calcium intake in low-income post-menopausal women of all racial and ethnic groups
Participation in food assistance programs was associated with calcium intake in black women only
Acculturation was associated with lower calcium intake among Mexican-Americans.

Author Conclusion:

In conclusion, our study highlights important socio-economic differences in BMD among ethnic groups of post-menopausal women
Education is likely to play an important role in improving calcium intake among low-income women
The Food Stamp Program is the largest food assistance program in the United States, serving about 20 million Americans and costing over $20 billion annually
Provision of osteoporosis-related nutrition education by United States government food assistance programs may be warranted to make the Food Stamp Program more effective in improving the calcium nutrition of older women.

Funding Source:

Government:

USDA Economic Research Service Agreement 43-3AEM-8-80052

Reviewer Comments:

Because no information is provided on the NHANES data collection, it is difficult to determine if the sample was free from bias
It is unclear to this reviewer how height and weight were obtained. Since this data is used in the results and summary, it would be useful to know how NHANES measured or collected this information.
Physical activity, smoking, and years since menopause were determined based on interview, resulting in possible reporting error as to how vigorous the physical activty was and how many cigarettes were smoked daily
The initial N was cited as 2,905 women, but in Table One, the Ns were specified as follows: White, 1,351, black, 581 and Mexican-American, 478; totaling 2,410. The reviewer was unable to determine the race of the remaining 495 women (2,905 minus 2,410).
No information was provided on the health status of participants or their use of medications that might affect physical activity, diet or bone density
Calcium intake was measured using a 24-hour recall. Because a person's can vary significantly from day to day, it is difficult to accurately measure calcium intake based on one 24-hour recall.

Authors note the following limitations:

About 10% of individuals who were examined did not have usable DXA data and about 24% either did not have usable DXA data or were missing relevant data
Data regarding receipt of government food assistance were limited to current or recent participation.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	N/A
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	N/A

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		???
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	???
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	???
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	???
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		???
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	???
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes