Awareness of cholesterol is a cornerstone to the prevention of CVD, yet our results show that women with one or more important risk factor tend to have less accurate knowledge of their cholesterol level than do women without such risk factors. Even health professionals underestimate their cholesterol levels and have only moderate knowledge of whether their cholesterol is elevated. In particular, cigarette smoking, lack of exercise, and obesity are all independently associated with decreased awareness of cholesterol levels. Despite their much greater risk of cardiovascular disease, women with untreated hypertension also have less awareness of cholesterol than those with treated hypertension, and women with diabetes are no more knowledgeable of their cholesterol levels than those without diabetes. Lower income and education also correlated with decreased cholesterol awareness, yet the significant associations of other risk factors with decreased awareness did not change after controlling for these variables.
Population-based surveys have demonstrated that awareness of cholesterol level is becoming more prevalent in the general population. In a recent survey, 71% of US adults reported that they had a cholesterol screening within the previous 5 years,9
and in a separate study, 49% of US adults surveyed in 2001 reported that they knew their total cholesterol.7
In 2000, Harawa et al.23
found that 23% of those ≥55 reported HDL, and in a 2003 American Heart Association National Study, Mosca et al.11
found that 29% of women reported knowing their HDL level. In comparison to our data obtained 10 years ago, the evidence from recent studies indicated only a slight increase with time in levels of cholesterol awareness.
While overall cholesterol awareness was higher among participants in the WHS, the factors affecting awareness were generally consistent with findings from previous studies. Two previous studies4,6
found poorer cholesterol knowledge among current smokers and sedentary people. Lower income and educational levels were also associated with decreased cholesterol awareness across studies.4,6,23,24
also reported lower cholesterol screening and lower knowledge among blacks than among whites, but our results suggest that racial differences may not be present among people with similar occupations. Previous studies had equivocal results about the relationships of diabetes, BMI, and alcohol consumption with cholesterol awareness. Although one report4,10
suggested better knowledge of cholesterol levels among those with diabetes and obesity, other reports failed to demonstrate this association.6,24
Thus, the differences in our results might be because of comparable educational levels in our population and greater knowledge of risk factors than in the general population. Our finding of greater awareness of cholesterol among users of HRT is consistent with other evidence of better health care knowledge among users of HRT during the study period.25
Previous studies with smaller samples12–18
have examined factors related to the validity of self-reported total cholesterol. In a study of 192 adults, Bowlin et al.12
found that women underreported their cholesterol by an average of 1 mg/dL, and men underreported it by an average of 3 mg/dL. In addition to problems with recall, differences between reported and measured cholesterol might also be because of the natural seasonal and diurnal variability of cholesterol or to assay variability across laboratories. Our main finding on validity is that personal characteristics had little ability to explain the discrepancies between reported and measured cholesterol (R2
.01); observed differences were equivalently substantial across all major subgroups of our population.
Limitations of self-reported cholesterol include errors in recall of measured values and changes in lifestyle that may affect cholesterol. Indeed, changes in diet or initiation of medications affecting cholesterol such as hormone therapy since last assessment of cholesterol would increase differences between measured and self-reported cholesterol levels. Initiation of lipid-lowering therapy would also influence cholesterol levels, although women would presumably have their cholesterol checked after beginning such treatment. We asked women to report their cholesterol level if checked within the past 5 years. A narrower window would probably have decreased the average difference between self-reported and measured cholesterol, although it would also likely have introduced potential selection bias because of a greater number of missing values. Indeed, Adult Treatment Panel III1
recommends screening of lipid profiles every 5 years in low risk persons, so a narrower window would be expected to selectively eliminate such people. Despite the clear limitations of self-reported cholesterol, it was a strong predictor of subsequent cardiovascular events. Self-reported cholesterol may represent a person’s integration of several recent cholesterol measurements, and to health professionals, may be useful for risk stratification. Furthermore, our results suggest that women with elevated cholesterol who do not know their level may be at a particularly increased risk of CVD, further emphasizing the value of cholesterol knowledge.
Other limitations of our study include the restricted range of occupations and the inclusion of women willing to participate in this trial. This limits the generalizability of overall rates, and the observed 84% of women who reported their TC levels is surely higher than that of the general population. Nonetheless, use of this population can enhance the validity of relationships between risk factors and cholesterol knowledge because of the more reliable reporting of other risk factors. This study also addresses the role of cholesterol knowledge when controlled for socioeconomic status. Furthermore, the observed 10 mg/dL difference between self-reported and measured cholesterol likely provides lower bounds on these discrepancies in the general population. In addition to the above limitation, our data on HDL were collected at 48-month follow-up; validity of this self-report might have improved with contemporaneous blood samples. Also, LDL awareness was not assessed in this study because TC was still being recommended by contemporary NCEP II guidelines as an initial screen for hypercholesterolemia and an overall marker of cholesterol status in patients on cholesterol therapy.2
The results suggest that cholesterol education programs should especially target persons with one or more additional cardiovascular risk factors because of their greater risk of CVD and their likely poorer knowledge of their cholesterol level. Although there are clear limitations to the accuracy of cholesterol knowledge, people should know that their lack of awareness of elevated cholesterol is associated with an increased risk of subsequent CVD and take steps to reduce this risk.