Reducing Women’s Risk of Heart Disease
By Timothy T. Brown, PhD
Our study, which was published in a recent issue of Health Economics, used information on approximately 7,000 people ages 44 through 88 who were enrolled in the Health and Retirement Study, which interviews individuals every 2 years about their health and other issues. We used information from five waves of the survey from 1996 to 2004.
Our analysis used specialized statistical techniques to mimic the results that would be found in a randomized controlled trial. This type of research is significant because it allows researchers to uncover causal connections at a fraction of the cost of a randomized trial and in a much shorter time frame. Once these relationships are uncovered, then focused randomized trials can explore the biological details and whether outcomes vary with variation in types of treatment.
The most surprising finding in my own research was that we only found a causal effect for women and no effect for men. The physician who was part of the study suggested that this was likely due to the fact that women develop cardiovascular disease approximately 10 years later than men do. Due to the protective effect of estrogen and other factors, women tend not to develop cardiovascular disease until after the onset of menopause. Women who receive dental care at the time they are beginning to lose the protective effect of estrogen may receive greater protective effects than men of the same age, who will tend to have more advanced cardiovascular disease.
In fact, we think that if we had conducted the study on a younger group of men and women, we would have found the reverse effect: a strong effect for men and no effect for women. This is because in a younger group, men would be at an earlier stage of cardiovascular disease development, a stage when dental care may be more effective, while premenopausal women would still be experiencing the protective effect of estrogen and other factors, making dental care less important. The lesson is that randomized trials that analyze the effect of periodontal treatment on individuals with established heart disease are less likely to find any significant relationship, because it appears that such care would mainly be effective in the early stages of cardiovascular disease.
This type of research has large implications for carefully determining the association between oral and systemic health. Health economists have long studied large data sets using specialized econometric techniques and are often able to determine causal associations that often would have been entirely missed without these techniques. For example, although all individuals benefit from regular dental care, women may benefit by visiting more frequently, and by maintaining a sound hygiene regimen, including brushing at least twice a day and flossing at least once a day.
At this point we are interested in replicating our study using a younger group of individuals to determine if we find positive results only for men and not for women. We are also interested in determining the cost implications of our findings. In particular, we are interested in determining how much the cost of treating heart disease would be lowered if more individuals were covered by dental insurance.
The Effect of Dental Care on Cardiovascular Disease Outcomes: An Application of Instrumental Variables in the Presence of Heterogeneity and Self-Selection
Brown TT, Cruz ED, Brown SS.
Featured in Health Economics.
2010 Sep 29. [Epub ahead of print]
Studies show a relationship between oral inflammatory processes and cardiovascular risk factors, suggesting that dental care may reduce the risk of cardiovascular disease (CVD) events. However, due to the differences between men and women in the development and presentation of CVD, such effects may vary by sex. We use a valid set of instrumental variables to evaluate these issues and include a test of essential heterogeneity. CVD events include new occurrences of heart attack (including death from heart attack), stroke (including death from stroke), angina, and congestive heart failure. Controls include age, race, education, marital status, foreign birthplace, and cardiovascular risk factors (health status, body mass index, alcohol use, smoking status, diabetes status, high-blood-pressure status, physical activity, and depression). Our analysis finds no evidence of essential heterogeneity. We find the minimum average treatment effect for women to be -0.01, but find no treatment effect for men. This suggests that women who receive dental care may reduce their risk of future CVD events by at least one-third. The findings may only apply to married middle-aged and older individuals as the data set is only representative for this group.
About the Author
Timothy T. Brown, PhD
Associate Director for Research
Berkeley Center for Health Technology
Assistant Adjunct Professor of Health Economics
School of Public Health
University of California at Berkeley