the design and baseline characteristics of the whi have been described in detail elsewhere ( 8) . in brief , the whi enrolled postmenopausal women 5079 years of age who provided written informed consent and had an expected survival and local residency of 3 years . exclusion criteria included current alcoholism , drug dependency , dementia , or other conditions that would limit full participation in the study . a total of 161,808 women ( 68,132 in clinical trials and 93,676 in an observational study ) were enrolled in the whi between 1993 and 1998 . data used in this report were obtained from women at baseline and then at periodic follow - up points over an average of 10.4 years . the protocol and consent forms were approved by the institutional review boards of all participating institutions . prevalent diabetes was defined as a self - report at baseline of  ever having received a physician diagnosis of diabetes when not pregnant . incident diabetes was based on data collected at annual follow - up visits at which participants were asked ,  since the date given on the front of this form , has a doctor prescribed any of the following pills or treatments ?  choices included cases of incident treated diabetes reported as of 31 august 2009 were included in the analysis . a study of the accuracy of self - reported diabetes conducted in a subset of whi participants indicated that self - reported disease status was a reasonably valid indicator of diagnosed diabetes when compared with medication and laboratory criteria ( 9 ) . however , self - report fails to identify undiagnosed diabetes and tends to underestimate diabetes prevalence and incidence in our study group ( 9 ) . at baseline , whi participants self - reported their race / ethnicity , choosing from non - hispanic white ( referred to hereafter as white ) , non - hispanic black ( referred to hereafter as black ) , hispanic , american indian / alaska native , asian ( ancestry was chinese , indo - chinese , korean , japanese , pacific islander , or vietnamese ) , and other . we excluded 1,849 women who reported race / ethnicity as  other  and 413 women without race / ethnicity information . the sample size was limited among american indians ( n = 714 ) ; therefore , analyses were restricted to whites , blacks , hispanics , and asians . body weight , height , and waist circumference were measured at baseline and year 3 . demographic and health history data were self - reported at baseline and included age , years of education , cigarette smoking status , family history of diabetes , and hormone therapy use . the baseline physical activity questionnaire asked about usual frequency and duration of several types of recreational and household activities using a standardized classification of physical activity intensity ( 10 ) . total energy expenditure was summarized in metabolic equivalent ( met ) hours per week ( met - h / week ) , computed as the summed product of frequency , duration , and intensity for reported activities . participants also completed a standardized food frequency questionnaire ( ffq ) developed for the whi to estimate average daily nutrient intake over the 3-month period prior to baseline visit ( 11 ) . dietary quality , assessed by the alternate healthy eating index ( ahei ) ( 12,13 ) , was computed based on food items and nutrients derived from the ffq , including 1 ) fruit , 2 ) vegetables , 3 ) nuts and legumes , 4 ) ratio of white to red meat , 5 ) total dietary fiber , 6 ) trans - fat , 7 ) ratio of polyunsaturated fat to saturated fat , 8) alcohol , and 9 ) multivitamin use . the reliability and validity of physical activity measurements were assessed among a random sample of 536 participants by a second measure of physical activity 10 weeks after the first measure . the test - retest reliability ( weighted  ) for the physical activity variables ranged from 0.53 to 0.72 , and the intraclass correlation for the total physical activity variable was 0.77 ( 8) . for the ffq , we assessed bias and precision of the ffq by comparing the intake of 30 nutrients estimated from the ffq with means from four 24-h dietary recalls and a 4-day food record from 113 women who participated in the whi ( 11 ) . for most nutrients , means estimated by the ffq were within 10% of the records or recalls . energy - adjusted correlation coefficients ranged from 0.2 ( vitamin b12 ) to 0.7 ( magnesium ) , with a mean of 0.5 . we concluded that the ffq produced nutrient estimates , which were similar to those obtained in other studies comparing short - term dietary recall and recording methods . we acknowledge that the reliability and validity are not perfect ; however , they provided reasonable measures in a large clinical trial , as published by several of our authors in high - impact articles ( 1416 ) . racial / ethnic differences in the prevalence of diabetes were assessed using logistic regression and are expressed as odds ratios ( ors ) and associated 95% cis , with whites used as the reference group . we present four logistic regression models : 1 ) unadjusted , including only race / ethnicity as a covariate ; 2 ) age - adjusted ; 3 ) adjusted for multiple potential confounding factors , including study arm , baseline age , bmi , waist circumference , physical activity , dietary quality , and smoking status ; and 4 ) adjusted for the same covariates as in model 3 plus educational attainment . among women who were free of diabetes at baseline , incidence rate was calculated as the number of newly reported postbaseline diabetes cases divided by total follow - up time in person - years . the time to diabetes ( i.e. , time to event ) was calculated as the interval between enrollment date and the earliest of the following : 1 ) date of annual medical history update when new diagnosis of diabetes and initiation of treatment for diabetes were ascertained ( observed event ) ; 2 ) date of last annual medical update during which participants were identified to be without diabetes ( censored event ) ; or 3 ) date of death from any cause ( censored event ) . cox proportional hazards models were used to estimate the hazard ratios ( hrs ) and associated 95% ci of incident diabetes , with whites used as the reference group . four cox regression models that parallel those described for the analysis of diabetes prevalence are presented . to identify determinants of diabetes incidence that might vary by racial / ethnic group , the impact of several covariates was evaluated by assessing the extent to which the hr estimate for a specific race / ethnicity group changed when each covariate was added individually to the unadjusted model . the percentage change in hr between the model with and without the covariate was used to describe the contribution of each covariate , considered singly , to diabetes risk estimated by race / ethnic group . to identify the most parsimonious prediction model , a stepwise cox proportional hazards regression analysis was conducted ( p values for entry = 0.25 and for retaining in the model = 0.05 ) . subgroup analyses also were conducted by race / ethnicity . weight change from baseline to 3 years was evaluated in relation to risk of incident disease by race / ethnicity among women who reported being free of diabetes at the 3-year measurement point . a similar analysis was conducted for waist circumference . to assess how the combined role of healthy lifestyle habits in diabetes prevention may vary by race / ethnicity ( 6,7 ) , categories of four modifiable lifestyle factors were defined as follows : physical activity ( upper vs. lower two tertiles ) , dietary quality score ( upper vs. lower two tertiles ) , smoking ( nonsmokers vs. past and former smokers combined ) , and bmi ( < 25 vs. 25 kg / m ) . in subgroup analyses by race / ethnicity , hrs and 95% cis were calculated for diabetes incidence for each lifestyle risk factor individually and several lifestyle factors in aggregate , adjusting for age , family history of diabetes , hormone therapy use , study arm , and lifestyle risk factors not already included in the model . the design and baseline characteristics of the whi have been described in detail elsewhere ( 8) . in brief , the whi enrolled postmenopausal women 5079 years of age who provided written informed consent and had an expected survival and local residency of 3 years . exclusion criteria included current alcoholism , drug dependency , dementia , or other conditions that would limit full participation in the study . a total of 161,808 women ( 68,132 in clinical trials and 93,676 in an observational study ) were enrolled in the whi between 1993 and 1998 . data used in this report were obtained from women at baseline and then at periodic follow - up points over an average of 10.4 years . the protocol and consent forms were approved by the institutional review boards of all participating institutions . prevalent diabetes was defined as a self - report at baseline of  ever having received a physician diagnosis of diabetes when not pregnant . incident diabetes was based on data collected at annual follow - up visits at which participants were asked ,  since the date given on the front of this form , has a doctor prescribed any of the following pills or treatments ?  choices included cases of incident treated diabetes reported as of 31 august 2009 were included in the analysis . a study of the accuracy of self - reported diabetes conducted in a subset of whi participants indicated that self - reported disease status was a reasonably valid indicator of diagnosed diabetes when compared with medication and laboratory criteria ( 9 ) . however , self - report fails to identify undiagnosed diabetes and tends to underestimate diabetes prevalence and incidence in our study group ( 9 ) . at baseline , whi participants self - reported their race / ethnicity , choosing from non - hispanic white ( referred to hereafter as white ) , non - hispanic black ( referred to hereafter as black ) , hispanic , american indian / alaska native , asian ( ancestry was chinese , indo - chinese , korean , japanese , pacific islander , or vietnamese ) , and other . we excluded 1,849 women who reported race / ethnicity as  other  and 413 women without race / ethnicity information . the sample size was limited among american indians ( n = 714 ) ; therefore , analyses were restricted to whites , blacks , hispanics , and asians . body weight , height , and waist circumference were measured at baseline and year 3 . demographic and health history data were self - reported at baseline and included age , years of education , cigarette smoking status , family history of diabetes , and hormone therapy use . the baseline physical activity questionnaire asked about usual frequency and duration of several types of recreational and household activities using a standardized classification of physical activity intensity ( 10 ) . total energy expenditure was summarized in metabolic equivalent ( met ) hours per week ( met - h / week ) , computed as the summed product of frequency , duration , and intensity for reported activities . participants also completed a standardized food frequency questionnaire ( ffq ) developed for the whi to estimate average daily nutrient intake over the 3-month period prior to baseline visit ( 11 ) . dietary quality , assessed by the alternate healthy eating index ( ahei ) ( 12,13 ) , was computed based on food items and nutrients derived from the ffq , including 1 ) fruit , 2 ) vegetables , 3 ) nuts and legumes , 4 ) ratio of white to red meat , 5 ) total dietary fiber , 6 ) trans - fat , 7 ) ratio of polyunsaturated fat to saturated fat , 8) alcohol , and 9 ) multivitamin use . the reliability and validity of physical activity measurements were assessed among a random sample of 536 participants by a second measure of physical activity 10 weeks after the first measure . the test - retest reliability ( weighted  ) for the physical activity variables ranged from 0.53 to 0.72 , and the intraclass correlation for the total physical activity variable was 0.77 ( 8) . for the ffq , we assessed bias and precision of the ffq by comparing the intake of 30 nutrients estimated from the ffq with means from four 24-h dietary recalls and a 4-day food record from 113 women who participated in the whi ( 11 ) . for most nutrients , means estimated by the ffq were within 10% of the records or recalls . energy - adjusted correlation coefficients ranged from 0.2 ( vitamin b12 ) to 0.7 ( magnesium ) , with a mean of 0.5 . we concluded that the ffq produced nutrient estimates , which were similar to those obtained in other studies comparing short - term dietary recall and recording methods . we acknowledge that the reliability and validity are not perfect ; however , they provided reasonable measures in a large clinical trial , as published by several of our authors in high - impact articles ( 1416 ) . racial / ethnic differences in the prevalence of diabetes were assessed using logistic regression and are expressed as odds ratios ( ors ) and associated 95% cis , with whites used as the reference group . we present four logistic regression models : 1 ) unadjusted , including only race / ethnicity as a covariate ; 2 ) age - adjusted ; 3 ) adjusted for multiple potential confounding factors , including study arm , baseline age , bmi , waist circumference , physical activity , dietary quality , and smoking status ; and 4 ) adjusted for the same covariates as in model 3 plus educational attainment . among women who were free of diabetes at baseline , incidence rate was calculated as the number of newly reported postbaseline diabetes cases divided by total follow - up time in person - years . the time to diabetes ( i.e. , time to event ) was calculated as the interval between enrollment date and the earliest of the following : 1 ) date of annual medical history update when new diagnosis of diabetes and initiation of treatment for diabetes were ascertained ( observed event ) ; 2 ) date of last annual medical update during which participants were identified to be without diabetes ( censored event ) ; or 3 ) date of death from any cause ( censored event ) . cox proportional hazards models were used to estimate the hazard ratios ( hrs ) and associated 95% ci of incident diabetes , with whites used as the reference group . four cox regression models that parallel those described for the analysis of diabetes prevalence are presented . to identify determinants of diabetes incidence that might vary by racial / ethnic group , the impact of several covariates was evaluated by assessing the extent to which the hr estimate for a specific race / ethnicity group changed when each covariate was added individually to the unadjusted model . the percentage change in hr between the model with and without the covariate was used to describe the contribution of each covariate , considered singly , to diabetes risk estimated by race / ethnic group . to identify the most parsimonious prediction model , a stepwise cox proportional hazards regression analysis was conducted ( p values for entry = 0.25 and for retaining in the model = 0.05 ) . subgroup analyses also were conducted by race / ethnicity . weight change from baseline to 3 years was evaluated in relation to risk of incident disease by race / ethnicity among women who reported being free of diabetes at the 3-year measurement point . a similar analysis was conducted for waist circumference . to assess how the combined role of healthy lifestyle habits in diabetes prevention may vary by race / ethnicity ( 6,7 ) , categories of four modifiable lifestyle factors were defined as follows : physical activity ( upper vs. lower two tertiles ) , dietary quality score ( upper vs. lower two tertiles ) , smoking ( nonsmokers vs. past and former smokers combined ) , and bmi ( < 25 vs. 25 kg / m ) . in subgroup analyses by race / ethnicity , hrs and 95% cis were calculated for diabetes incidence for each lifestyle risk factor individually and several lifestyle factors in aggregate , adjusting for age , family history of diabetes , hormone therapy use , study arm , and lifestyle risk factors not already included in the model . at baseline , the average age of the 158,833 women with evaluable data was 63 years . the racial / ethnic distribution was 84.1% white , 9.2% black , 4.1% hispanic , and 2.6% asian . blacks and hispanics tended to have more risk factors , whereas asians tended to have fewer ( table 1 ) . baseline characteristics of participants in the whi 19932009 ( n = 158,833 ) at enrollment , diabetes prevalence was highest among blacks ( 12.2% ) , followed by hispanics ( 7.2% ) , asians ( 5.9% ) , and whites ( 3.3% ) ( table 2 ) . compared with the unadjusted ors , which were significantly higher in all three race / ethnic groups when compared with whites , the age - adjusted and multivariable - adjusted ors were attenuated for blacks and hispanics but strengthened for asians . additional adjustment for educational attainment further attenuated the ors for blacks and hispanics ; however , ors for all three racial / ethnic minority groups remained significantly higher than that of whites . prevalence and incidence of diabetes in the whi 19932009 during an average of 10.4 years ( sd = 3.2 ) of follow - up , 14,604 new cases of diabetes were reported ( 11,127 whites , 2,181 blacks , 879 hispanics , and 417 asians ) , with incidence being highest in blacks and lowest in whites . compared with whites , unadjusted analyses showed a significantly higher diabetes incidence of 136% in blacks , 114% in hispanics , and 43% in asians . after adjusting for age , study arm , bmi , physical activity , smoking status , and educational attainment , 1 ) , the highest cumulative incidence of diabetes was seen among women who had both high bmi and low levels of physical activity . the cumulative incidence of diabetes was 23.4% among black women who were both obese and in the lowest tertile of physical activity , but decreased to 8.8% in those who had a healthy weight and exercised . white women who were overweight ( bmi = 2529.9 kg / m ) and in the lowest tertile of physical activity had a cumulative incidence of 8.7% , whereas white women who were obese ( bmi 30 kg / m ) and in the lowest tertile of physical activity had a cumulative incidence of 18.6% . across all racial / ethnic groups , women who were normal weight ( bmi < 25 kg / m ) and in the highest tertile of physical activity had less than one - third to one - sixth the incidence of diabetes compared with women with bmi 30 kg / m and in the lowest tertile of physical activity . cumulative incidence of diabetes by race / ethnicity , physical activity level , and bmi category . analyses conducted to estimate the influence of individual factors that may account for the observed racial / ethnic variation in diabetes incidence by comparing hrs obtained from unadjusted versus fully adjusted models ( results not shown ) revealed that if asian women had the same waist circumference , bmi , and dietary quality intake as whites , their hr for diabetes would be increased by 44 , 29 , and 3.5% , respectively . among blacks , if they had the same bmi , waist circumference , family history of diabetes , dietary quality intake , and physical activity levels as whites , their hr for diabetes would be decreased by 25 , 19 , 11 , 7 , and 6% , respectively . among hispanics , if they had the same educational attainment , bmi , family history of diabetes , dietary quality intake , and physical activity levels as whites , their hr for diabetes would be decreased by 14 , 10 , 9 , 7 , and 6% , respectively . results from the stepwise cox proportional hazards regression analysis conducted to identify the most parsimonious predictive model for diabetes incidence , fitting candidate predictors plus race / ethnicity , showed that race / ethnicity , age , bmi , waist circumference , education , smoking status , physical activity , family history of diabetes , and dietary quality score entered the model . hrs of incident diabetes corresponding to single and specific combinations of lifestyle risk factors in race / ethnicity subgroups in the whi 19932009 subgroup analyses by race / ethnicity ( results not shown ) conducted to assess the effect of interval ( i.e. , baseline to 3 years ) changes in factors found to be significant in the cox proportional hazards models revealed a significant effect of 5% increased risk of diabetes for each 5-cm increase in waist circumference ( hr 1.05 [ 95% ci 1.041.07 ] ) . the observed effect was consistent across all race / ethnicity groups . an alternative model fit to assess if weight gain could explain some of the observed racial / ethnic variation in diabetes incidence revealed an 3% increase in subsequent risk for each 1-kg / m increment in bmi ( 1.03 [ 1.021.04 ] ) . higher levels of physical activity , better diet , and having a healthy weight tended to be associated with a significantly lower risk of diabetes in each racial / ethnic group , with some exceptions . whites , blacks , and hispanics with all factors in the low - risk category ( 4.0 , 1.1 , and 2.2% ) had 60 , 69 , and 63% lower risk for incident diabetes ( table 3 ) . healthy weight ( bmi < 25 kg / m ) demonstrated the greatest role in reducing risk of diabetes in each racial / ethnic group : 66% in whites , 55% in blacks , 64% in hispanics , and 66% in asians . at baseline , the average age of the 158,833 women with evaluable data was 63 years . the racial / ethnic distribution was 84.1% white , 9.2% black , 4.1% hispanic , and 2.6% asian . blacks and hispanics tended to have more risk factors , whereas asians tended to have fewer ( table 1 ) . at enrollment , diabetes prevalence was highest among blacks ( 12.2% ) , followed by hispanics ( 7.2% ) , asians ( 5.9% ) , and whites ( 3.3% ) ( table 2 ) . compared with the unadjusted ors , which were significantly higher in all three race / ethnic groups when compared with whites , the age - adjusted and multivariable - adjusted ors were attenuated for blacks and hispanics but strengthened for asians . additional adjustment for educational attainment further attenuated the ors for blacks and hispanics ; however , ors for all three racial / ethnic minority groups remained significantly higher than that of whites . prevalence and incidence of diabetes in the whi 19932009 during an average of 10.4 years ( sd = 3.2 ) of follow - up , 14,604 new cases of diabetes were reported ( 11,127 whites , 2,181 blacks , 879 hispanics , and 417 asians ) , with incidence being highest in blacks and lowest in whites . compared with whites , unadjusted analyses showed a significantly higher diabetes incidence of 136% in blacks , 114% in hispanics , and 43% in asians . after adjusting for age , study arm , bmi , physical activity , smoking status , and educational attainment , 1 ) , the highest cumulative incidence of diabetes was seen among women who had both high bmi and low levels of physical activity . the cumulative incidence of diabetes was 23.4% among black women who were both obese and in the lowest tertile of physical activity , but decreased to 8.8% in those who had a healthy weight and exercised . white women who were overweight ( bmi = 2529.9 kg / m ) and in the lowest tertile of physical activity had a cumulative incidence of 8.7% , whereas white women who were obese ( bmi 30 kg / m ) and in the lowest tertile of physical activity had a cumulative incidence of 18.6% . across all racial / ethnic groups , women who were normal weight ( bmi < 25 kg / m ) and in the highest tertile of physical activity had less than one - third to one - sixth the incidence of diabetes compared with women with bmi 30 kg / m and in the lowest tertile of physical activity . cumulative incidence of diabetes by race / ethnicity , physical activity level , and bmi category . analyses conducted to estimate the influence of individual factors that may account for the observed racial / ethnic variation in diabetes incidence by comparing hrs obtained from unadjusted versus fully adjusted models ( results not shown ) revealed that if asian women had the same waist circumference , bmi , and dietary quality intake as whites , their hr for diabetes would be increased by 44 , 29 , and 3.5% , respectively . among blacks , if they had the same bmi , waist circumference , family history of diabetes , dietary quality intake , and physical activity levels as whites , their hr for diabetes would be decreased by 25 , 19 , 11 , 7 , and 6% , respectively . among hispanics , if they had the same educational attainment , bmi , family history of diabetes , dietary quality intake , and physical activity levels as whites , their hr for diabetes would be decreased by 14 , 10 , 9 , 7 , and 6% , respectively . results from the stepwise cox proportional hazards regression analysis conducted to identify the most parsimonious predictive model for diabetes incidence , fitting candidate predictors plus race / ethnicity , showed that race / ethnicity , age , bmi , waist circumference , education , smoking status , physical activity , family history of diabetes , and dietary quality score entered the model . hrs of incident diabetes corresponding to single and specific combinations of lifestyle risk factors in race / ethnicity subgroups in the whi 19932009 subgroup analyses by race / ethnicity ( results not shown ) conducted to assess the effect of interval ( i.e. , baseline to 3 years ) changes in factors found to be significant in the cox proportional hazards models revealed a significant effect of 5% increased risk of diabetes for each 5-cm increase in waist circumference ( hr 1.05 [ 95% ci 1.041.07 ] ) . the observed effect was consistent across all race / ethnicity groups . an alternative model fit to assess if weight gain could explain some of the observed racial / ethnic variation in diabetes incidence revealed an 3% increase in subsequent risk for each 1-kg / m increment in bmi ( 1.03 [ 1.021.04 ] ) . higher levels of physical activity , better diet , and having a healthy weight tended to be associated with a significantly lower risk of diabetes in each racial / ethnic group , with some exceptions . whites , blacks , and hispanics with all factors in the low - risk category ( 4.0 , 1.1 , and 2.2% ) had 60 , 69 , and 63% lower risk for incident diabetes ( table 3 ) . kg / m ) demonstrated the greatest role in reducing risk of diabetes in each racial / ethnic group : 66% in whites , 55% in blacks , 64% in hispanics , and 66% in asians . previous reports , mainly focused on younger men and women , have indicated significant racial / ethnic disparities in diabetes in the u.s . ( 1,4,5 ) . the 20072009 national health interview survey found that 7.1% of whites , 8.4% of asians , 11.8% of hispanics , and 12.6% of blacks reported having a diagnosis of diabetes ( 1 ) . the whi allows a unique opportunity to deepen understanding of the patterns and determinants of diabetes in older women , including racial / ethnic minorities that represent growing segments of the u.s . we found that the prevalence and incidence of diabetes ranged from approximately two to three times higher in blacks and approximately two times higher in hispanics and in asians , compared with whites . observed racial / ethnic differences in diabetes incidence were explained , in large part , by modifiable lifestyle factors that included diet quality , physical activity , and smoking status or factors resulting from lifestyle behaviors including bmi and waist circumference . adjustment for differences in these variables indicates that asians have the highest inherent risk , though women of all four racial / ethnic groups would experience a large reduction in diabetes risk by maintaining a healthy body weight , healthy diet , and a physically active lifestyle . maintaining a bmi < 25 kg / m appears to be particularly important , and interval changes in both bmi and waist circumference predicted newly incident disease . in this study , both bmi and waist circumference were found to be related to prevalent diabetes , and interval changes were associated with risk of incident disease . because waist circumference reflects centralized obesity , and the propensity toward large waist circumference varies according to race / ethnicity , its effect may differ from that of bmi ( 17,18 ) . although bmi and waist circumference among asian , postmenopausal women in the whi were relatively lower than whites , asians were at higher risk of diabetes at lower levels of bmi and with smaller waist circumferences ( i.e. , by 44 and 29% , respectively ) compared with whites , a result consistent with that seen in the multi - ethnic study of atherosclerosis ( 19 ) . our results on asians suggest that additional risk factors , which might be biological , social , or a combination , drive the higher prevalence and incidence of diabetes in this population . diabetes risk in blacks with the same bmi and waist circumference as whites was lower by 25 and 17% , respectively . similarly , diabetes risk in hispanics with the same bmi and waist circumference as whites was lower by 10 and 2% , respectively . we noted that within each group , bmi was the most important determinant for diabetes incidence . physical inactivity also was found to be associated with increased risk of diabetes in all groups . in a previous publication using whi data , we reported the association between physical inactivity and development of diabetes ( 20 ) . our present study showed that , compared with whites , given the same level of physical activity , the risk for diabetes for blacks and hispanics is 6% lower . several studies have found differences in dietary intake by race / ethnicity ( 26,27 ) . although their diet quality was better than that of whites , we found , for example , if their overall dietary quality were to decrease to that of whites , their risk of diabetes would increase by 4% relative to whites . in fact , if blacks and hispanics improved their diet to a quality similar to that of whites , their risk of diabetes would be 7% lower . although previous studies demonstrated that diabetes is preventable by relatively simple lifestyle modifications ( 6,7 ) , our data suggest that some minority groups might obtain greater benefit from improving lifestyle factors ( i.e. , blacks and hispanics ) than others ( i.e. , asians ) due to differences in the amount of change possible or the vulnerability to these factors . the divergent findings in asian women are of interest , suggesting that additional approaches to prevention deserve attention . for example , asians may need to achieve even greater weight loss to have the same low risk of diabetes as nonoverweight whites , and the world health organization already uses a lower bmi cut point for asians . the fact that asians in the whi had much healthier body weights at baseline set the stage for much lower overall diabetes risk . however , further research with this population is warranted because our statistical models , with additional covariates , may be unstable and less reliable due to small numbers . we found that blacks and hispanics are more sensitive to lifestyle modifications and weight loss than whites , and this is corroborated by our previous lifestyle intervention study results from a hispanic population ( 28 ) . hispanic sensitivity to the development of an insulin - resistant state or diabetes with lower weight gain is well described ( 29 ) . if confirmed in weight - loss studies , the sensitivity to modest weight loss that we observed in high - risk groups in the whi will have important clinical and public health implications . it will also be important to explore possible social and genetic underpinnings for such population sensitivity . two recent studies indicate that social economic status ( ses ) may account for some of the observed race / ethnicity disparities in diabetes prevalence ( 30,31 ) . similarly , in our study , adjustment for educational attainment resulted in the largest decrease in diabetes incidence in hispanics ; if hispanics had achieved the same education levels as whites , their risk of diabetes would be 14% lower . however , education is only one component of ses , and thus consideration of an adjustment for other ses parameters ( e.g. , income and occupation ) would likely account for a greater proportion of the disparities observed in black and hispanic women . first , observed prevalence of diabetes in the whi was lower than expected , as relatively healthy postmenopausal women were enrolled in the study . second , reported education level among black women in the whi was considerably higher than education level among black women in the u.s . the education differential for blacks and hispanics is much more extreme than that observed in whites , and this may underlie some of the other observations in the data ( 32,33 ) . however , observed patterns are consistent with the population - based literature in terms of race / ethnic patterns of diabetes prevalence and incidence of diabetes . third , asian women appear to have the greatest  inherent  risk in that their risk factor profile was in fact better than whites , and large increases in diabetes risk would occur if the risk factors deteriorate . ( 19 ) , which showed that asians had a higher diabetes risk per unit increase in bmi and waist circumference . recognizing that each of the racial / ethnic groups is heterogeneous due to differences by national origin and other relevant parameters fourth , it is encouraging to note the effect of interval changes in weight amounting to a 3% reduction in risk of diabetes for each unit decrease in bmi . individual efforts to reduce weight and increase physical activity are difficult to sustain ; however , current efforts are underway to tackle weight regulation through a variety of approaches that go beyond the individual . lessons from the tobacco literature indicate that behavior change is influenced by our social and political structure ; thus , multilevel approaches are likely needed . in the u.s . , the race / ethnicity categories used most often in medical and public health research are from self - report , the same as the u.s . census categories . genetic race / ethnicity information known as admixture data ( i.e. , ancestry - informative markers ) from another study indicates great diversity within all four of the groups that we examined ( 34 ) . yet , few studies obtain such data due to issues concerning cost , feasibility , practicality , and comparability . thus , the differences observed and reported here reflect any inherent biological differences across the groups studied as well as differences in life experiences ( e.g. , exposure to specific environments and stressors ) , which may also contribute to acquired physiological differences in reactivity , and in turn diabetes risk ( 35 ) . the challenges for interpreting the results associated with studying self - reported racial / ethnic groups will likely increase in future studies , as more people identify themselves as belonging to multiple racial / ethnic groups . although geographically diverse , racial / ethnic groups vary in their representation of the general population . data for whites show that many characteristics of the whi participants are similar to white women participating in the national health and nutrition examination survey ( 11 ) ; however , ethnic groups are underrepresented in the whi . women from parts of the country where we see large disparities in certain minorities ( e.g. , rural southern blacks ) were not represented . thus , both prevalence and racial differentials are smaller in the whi than what we might expect to see in the u.s . as a whole . second , only self - reported prevalence of diabetes and treated incident diabetes were ascertained ; thus , prevalence and incidence of diabetes may be underestimated . we acknowledge that this is a limitation , and we did not account for nontreated diabetes . however , self - reported diabetes in the whi was found to be reliable and sufficiently accurate to allow its use in epidemiologic studies ( 9 ) . third , there could be other factors for which we did not control that further contribute to racial / ethnic disparities , such as health care access ( 36 ) . however , > 90% of the whi participants had insurance coverage , and diabetes prevalence and incidence were assessed at regular study visits . fourth , although incident diabetes in older women is likely to be type 2 diabetes , the whi question did not specify type of diabetes . other limitations include missing data ; however , the rates of retention in the whi were > 95% during an average of 7 years of follow - up ( 37 ) . balancing the limitations , there are several major strengths . in addition , the whi collected detailed information on a comprehensive range of diabetes risk factors relevant to this investigation , with a 10-year follow - up for diabetes outcome . in conclusion , significant disparities exist between the major ethnic groups in diabetes prevalence and incidence in postmenopausal women ; these differences withstand adjustment for a very comprehensive group of physiological and behavioral risk factors . although these results highlight the potential benefits of tailored diabetes prevention strategies directed at those specific factors that are most likely to increase the risk of diabetes among each racial / ethnic group , it is prudent to recommend avoidance of weight gain , weight loss , a healthy diet , and adequate levels of physical activity to all postmenopausal women for the purpose of diabetes risk reduction .
objectiveto examine determinants of racial / ethnic differences in diabetes incidence among postmenopausal women participating in the women s health initiative.research design and methodsdata on race / ethnicity , baseline diabetes prevalence , and incident diabetes were obtained from 158,833 women recruited from 19931998 and followed through august 2009 . 
 the relationship between race / ethnicity , other potential risk factors , and the risk of incident diabetes was estimated using cox proportional hazards models from which hazard ratios ( hrs ) and 95% cis were computed.resultsparticipants were aged 63 years on average at baseline . 
 the racial / ethnic distribution was 84.1% non - hispanic white , 9.2% non - hispanic black , 4.1% hispanic , and 2.6% asian . 
 after an average of 10.4 years of follow - up , compared with whites and adjusting for potential confounders , the hrs for incident diabetes were 1.55 for blacks ( 95% ci 1.471.63 ) , 1.67 for hispanics ( 1.541.81 ) , and 1.86 for asians ( 1.682.06 ) . 
 whites , blacks , and hispanics with all factors ( i.e. , weight , physical activity , dietary quality , and smoking ) in the low - risk category had 60 , 69 , and 63% lower risk for incident diabetes . 
 although contributions of different risk factors varied slightly by race / ethnicity , most findings were similar across groups , and women who had both a healthy weight and were in the highest tertile of physical activity had less than one - third the risk of diabetes compared with obese and inactive women.conclusionsdespite large racial / ethnic differences in diabetes incidence , most variability could be attributed to lifestyle factors . 
 our findings show that the majority of diabetes cases are preventable , and risk reduction strategies can be effectively applied to all racial / ethnic groups .