Depression and Social Context
A 2001 meta-analysis demonstrated that the odds of finding clinically relevant depression among adults with diabetes was twice that among people without diabetes (odds ratio [OR] 2.0, 95% CI 1.8, 2.2). [
42] The prevalence of comorbid depression was significantly higher among diabetic women (28%) than diabetic men (18%), just as it is in the non-diabetic population. The OHS 1996–1997 data showed that the prevalence of depression among women with DM was 8.3%, as compared with 5.4% among women without DM; the comparable rates among men were much lower, at 3.6% and 2.5%. [
19] Depression in people with diabetes is associated with poor metabolic control and the use of more health care resources, even after differences in age, sex, race/ethnicity, health insurance and comorbidity are adjusted for. [
43] There are inadequate data on at-risk ethnic groups. [
44] Ethnic and sex differences in knowledge and health beliefs may affect diabetes self-care, as indicated by several small studies. [
45,
46] Further qualitative research is needed in this area.
Long-Term Complications of Diabetes
Diabetes is the most common cause of acquired blindness among adults in North America. [
56] Canadian data on visual problems and diabetic retinopathy are sparse. The prevalence of retinopathy at baseline in the U.K. Prospective Diabetes Study [
47] was comparable among women (35%) and men(39%). A 2002 study in the United Kingdom estimated the prevalence of blindness and partial sight in the general and diabetic populations (age-standardized), analyzing sex and ethnic differences. There was an almost threefold increase in the prevalence of blindness and partial sight in the diabetic population. [
47] Among those with DM, there was a higher proportion of visually impaired females than males and no overall ethnic differences. In the general population, there was a higher than expected proportion of visually impaired Indo-Asian people. The degree to which the visual loss was caused by diabetic retinopathy is not known. In the Ontario OHS 1996–1997, women with and without diabetes had a higher prevalence of visual problems not corrected by lenses than men. [
19] The prevalence of visual problems among women with DM (4.4%) was not statistically different from that of women without DM (2.4%).[
24] The prevalence of visual problems among men with and without DM was 1.9%and 1.7%.
Retinopathy is a microvascular complication of diabetes, and it is hypothesized that women with myocardial ischemia and normal coronary arteries may have microvascular disease. The U.S. Atherosclerosis Risk in Communities study found that retinal arteriolar narrowing was related to the risk of coronary heart disease (CHD) in women but not in men. [
48] Further studies involving women with diabetes are needed for confirmation of this finding.
Cardiovascular disease (CVD) is the leading cause of death among people with diabetes. From the NPHS 1996–1997 data it was estimated that the prevalence of self-reported, diagnosed cardiovascular disease (CHD and stroke) was 21% among people aged over 12 with DM versus 4% among those without DM (age-adjusted)[
12]. (These figures have to be interpreted with some caution, since using prevalence data to examine the risk of more fatal conditions such as CVD has some limitations.) Recent analyses based on the ODD showed that DM appears to reduce the difference in heart disease normally observed between men and women. In fact, acute myocardial infarction (MI) rates among women with DM exceeded those among men without DM. [
49] In contrast, the effect of DM on the risk of stroke appears to be similar for men and women. [
50]
The SHARE cohort study looked at cardiovascular risk and event rates in adults of three ethnic groups (South Asians, Chinese and Europeans) living in Hamilton, Toronto and Edmonton. [
51] South Asians had the highest prevalence of cardiovascular disease as compared with Europeans and Chinese (11%, 5%, and 2% respectively, p = 0.004). The rates of death from cerebrovascular disease (CBVD) were relatively low, and there was little ethnic variation among men. Among women, Chinese women had the highest rate of death from CBVD. A five-year chart review of hospital admissions for acute MI of South Asian Canadians at two hospitals within the metropolitan Toronto region revealed that they were more likely to have DM (43%) than patients not of South Asian origin (28%) (p < 0.001). [
52] However, South Asian Canadians did not differ from the other groups with respect to blood pressure or lipid status. Paradoxically, fewer South Asians smoked, a finding that would be expected to reduce the prevalence of heart disease. The underlying mechanisms contributing to the increased CHD and diabetes prevalence in the South Asian populations needs further basic research.
Knowledge about sex differences in the development and progression of diabetic nephropathy (kidney disease) in Canadians is limited. One 10-year prospective cohort study of 385 patients with type 2 DM addressed the impact of metabolic control and blood pressure control on the incidence and progression of nephropathy, but found no effect of sex. [
53] Two studies have suggested that males were more likely to develop DM nephropathy.[
54,
55] Further Canadian studies are needed with adequate representation of the ethnic groups at risk for DM, controlling for blood pressure and metabolic control.