This is the first study that examined trends of diabetes and diabetes-related complications among Mexican Americans aged ≥75 years. The prevalence of diabetes in this sample increased from 20.3% in 1993–1994 to 37.2% in 2004–2005. The prevalence of both microvascular and macrovascular diabetes complications and IADL disability did not change significantly between the two cohorts. However, the prevalence of having any lower-extremity disability did increase between the two cohorts. In addition, self-reported ADL disability also significantly increased among individuals with diabetes between the two time periods.
Our findings are consistent with previous reports showing a national continuous upward trend in diabetes prevalence over the previous decade. Reports from the Centers for Disease Control and Prevention have shown that the prevalence of diabetes among the general population aged ≥75 years increased from 10.4% in 1993 to 16.4% in 2005 (1
). Using the National Health Interview Survey (NHIS), the Centers for Disease Control and Prevention estimated the prevalence of diabetes among Mexican Americans aged ≥75 years in 2005 to be 28.5% (SEM 3.6), which was somewhat lower than our estimate of 37% for 2004–2005 (2.2) (1
Our data show no significant changes in diabetes-related visual impairment among individuals with diabetes over the period from 1993–1994 to 2004–2005. This is consistent with national findings from the NHIS indicating a nonsignificant change in visual impairment rates among individuals with diabetes aged ≥75 years from 32.4% (SEM 2.0) in 1997 to 27.1% (1.4) in 2007 (1
). Studies report a decrease in diabetes-related visual problems between the 1980s and the beginning of the 21st century resulting from improvements in screening and glycemic control (6
). This improvement may not be apparent in our study because of differences in study periods compared with other studies, the advanced age of our sample, and measures used.
Although no prevalence data for diabetes-related kidney problems have been reported, findings from the U.S. Renal Data System showed that incidence rate of end-stage renal disease (ESRD) among individuals with diabetes aged ≥75 years has increased significantly over the period from 1997 to 2002, whereas it decreased among those aged ≥65 years (16
). It is important to consider that our estimates measure any kidney disease related to diabetes, not ESRD specifically. The increase shown in ESRD presented in previous reports among those aged ≥75 years is again probably due to the increased survival of individuals with diabetes. Moreover, it could also reflect a concomitant increase in referral, admission rates, and intervention rather than an actual increase in ESRD incidence (6
Similar to the trends in microvascular complications, we did not find significant changes in the prevalence of macrovascular complications including cardiovascular disease and peripheral circulatory problems. These findings are similar to reports from the NHIS showing no significant changes in the prevalence of any cardiovascular disease among the general population aged ≥75 years over the period from 1997 to 2003 (1
). Because macrovascular conditions are not strongly related to hyperglycemia, improvement in diabetes management might not modify the prevalence of these conditions among individuals with diabetes (17
The higher prevalence of diabetes reported in this study might be partly due to changes in the diagnostic criteria. The cutoff point in glycemia for a diagnosis of diabetes was decreased from ≥140 to ≥126 mg/dl in 1997 (18
). This reduction may have had a substantial influence on the recent prevalence estimates for diabetes. The new diagnostic criteria are probably capturing individuals with diabetes at an earlier point in the disease. Reports have suggested that widespread use of the new criteria are capturing many individuals with undiagnosed diabetes, which may result in even higher prevalence estimates (18
Another explanation for the upward trend in diabetes is the concurrent increase in obesity in older Mexican Americans. As we have shown above, the prevalence of obesity has increased dramatically in this older population since the baseline interview in 1993–1994. Obesity is reported to be one of the most significant factors contributing to the development of diabetes and is highly prevalent in Hispanic populations (19
Mexican Americans are living longer but are living with more chronic conditions and more disability (9
). Older adults with diabetes are more likely to have functional disabilities and are more likely to use mobility aids compared with individuals without diabetes (20
). Consequently, more functional disability among individuals with diabetes could also lead to an overall reduction in active life expectancy.
Active life expectancy is an important consideration because the prevalence of diabetes has dramatically increased among Mexican Americans aged ≥75 years. It has been found that individuals with diabetes aged ≥75 years in the U.K. have experienced a significant reduction in active life expectancy in recent years, where individuals without diabetes had an extra 2 years of life without disability compared with individuals with diabetes in 1999 (21
). Similarly, a study consisting of older adults aged ≥65 years showed that those who do not have diabetes gain between 4 and 5 disability-free years of life (22
). Both diabetes and obesity contribute to a reduction in functional ability. Older adults who are obese are more likely to become disabled and, generally speaking, older adults are also less likely to recover compared with younger obese individuals (23
). As Mexican Americans age, specific attention to the pathways leading to this increase in obesity such as the reduction of adipose tissue in the abdominal area and dietary modifications could reduce functional disability and increase future active life expectancy.
There are several limitations to this study. The determination of a diabetes diagnosis was based on a self-reported measure and was not based on any clinical measure of fasting plasma glucose. In addition, the presence of diabetes-related complications was also based on self-report. However, these types of self-reported measures have been found to be a valid and reliable method of determining the presence of disease (24
). Nevertheless, underreporting may have occurred by not including those in whom diabetes has not yet been diagnosed, but who actually have the disease. In the U.S., it is estimated that there are 2.4 million individuals with undiagnosed diabetes. Moreover, many diagnoses are incidental and only occur when related complications emerge. New onset of diabetes in older individuals is not very common, meaning that oftentimes diabetes goes undiagnosed while other complications arise (25
In summary, in light of the high prevalence of diabetes in this group, no improvement in diabetes-related complications heightens the urgency for public health interventions. As diabetes is projected to become more prevalent in older adults in the future (2
), physicians need to be trained in early detection of diabetes among older adults and should encourage appropriate management in patients aged ≥75 years, including glycemic control and healthier lifestyles and adequate pharmacological treatment when indicated. Moreover, common clinical and physiological pathways between obesity and diabetes may allow the development of interventions that might improve diabetes-related complications and functional disability in this population.