Smoking and diabetic nephropathy

Survival of Diabetic Patients on Continuous Ambulatory Peritoneal Dialysis for over Five Years

Of 26 diabetic patients starting CAPD before July 1, 1981, six had survived over five years on this mode of dialysis. Considering as “withdrawn alive” those who received transplants or switched to hemodialysis, the one and five-year survival was 70% and 44% respectively. The six type I diabetics who survived over five years were young (mean age 31.8 ± 2 years at onset of CAPD), initially free of cardiac disease and predominantly non-smokers. On CAPD they had relatively low hospitalization rates, including admissions for peritonitis, and a peritonitis rate of one episode every 13.6 patient months. Blood pressure improved but most required therapy at five years. Vision was maintained, but four of six had bone fractures. Serum cholesterol increased with time; one patient had a silent myocardial infarct and two developed angina. As assessed by HgA1c, blood glucose control improved over predialysis values. Four of these six maintained their physical activities and two deteriorated. These results demonstrate that diabetic patients can survive for a long period on CAPD. We suggest that attention be focused on cardiac risk factors and that diabetic patients be encouraged to abstain from smoking.

Characteristics and comparison between diabetes mellitus and non-diabetes mellitus among chronic kidney disease patients: A cross-sectional study of the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE)

Although the prevalence of chronic kidney disease (CKD) and diabetes mellitus (DM) is increasing globally, information on Chinese CKD patients with DM is lacking. A total of 3499 pre-dialysis CKD patients from across China were enrolled in the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE) between November 2011 and April 2016. We divided the C-STRIDE patients into CKD with DM and CKD without DM groups and compared their clinical, demographic, and laboratory data in this cross-sectional study. CKD patients with DM were older, had a higher male-to-female ratio, and had more complications than CKD patients without DM. Age, smoking, and 24-h urinary protein levels were associated with co-occurrence of CKD and DM. Less than 50% of patients in either group took antilipemic, cardiovascular, cerebrovascular, or anti-anemic drugs. In addition, only 18.38% of CKD patients with DM had undergone a renal biopsy, and diabetic nephropathy was confirmed in 35.4% of them. Our findings suggest that several types of medication and renal biopsies should be used more frequently in the treatment of Chinese CKD patients with DM.

Microalbuminuria in long-term insulin-dependent diabetes mellitus. Prevalence and clinical characteristics in a normotensive population

Albumin excretion rate was determined by radioimmunoassay in overnight urine from 102 normotensive patients with insulin-dependent diabetes mellitus of more than 10 year's duration. Based on two samples, 16 patients (16%) exhibited microalbuminuria, defined as a mean excretion rate greater than 20 micrograms/min. Microalbuminuric patients were significantly younger at onset of diabetes but did not differ from normoalbuminuric patients concerning age or duration of diabetes. Nonetheless, diastolic and mean arterial blood pressures were significantly higher in the microalbuminuric group. The existing glycemic control, assessed by glycosylated hemoglobin (HbA1c) was better in normoalbuminurics, but not significantly so. The albumin excretion rate in microalbuminuric patients correlated significantly (p less than 0.01) to diastolic (r = 0.69) and to mean arterial blood pressure (r = 0.69), but did not correlate to HbA1c. Thus, it is concluded that even normotensive patients with signs of early diabetic nephropathy, i.e. microalbuminuria, exhibit small, but significant increases in blood pressure.

Cigarette smoking and incident chronic kidney disease: a systematic review

BACKGROUND

Several studies have examined the role of cigarette smoking in the development of renal disease in human populations. However, there have been no systematic reviews on the evidence linking smoking with incident renal disease.

METHODS

We performed an evidence-based evaluation of peer-reviewed research published during 1966-2005, from a search of five databases, including Ovid MEDLINE and EMBASE.

RESULTS

Of the 28 studies that were reviewed, 11 were excluded from the final analysis due to poor methodological quality (n = 6), no reported risk estimate for the association between smoking and kidney disease (n = 3), inability to find a Japanese translator (n = 1), and duplicate cohort (n = 1). Seventeen studies were included in the final analysis; seven studies found an overall significant association between smoking and incident chronic kidney disease, and three studies found a significantly increased risk of chronic kidney disease in current smokers that was gender and/or dose related. An increased risk of developing chronic kidney disease among smokers was significantly associated with male gender (relative risk 2.4, 95% confidence interval 1.2-4.5), >20 cigarettes smoked/day (odds ratio 1.51, 95% confidence interval 1.06-2.15, and relative risk 2.3, 95% confidence interval 1.2-4.3), and smoking >40 years (odds ratio 1.45, 95% confidence interval 1.00-2.09). A pooled estimate of the relative risk (meta-analysis) was deemed inappropriate due to the heterogeneity in methodologies utilized by the different studies.

CONCLUSIONS

This comprehensive review reveals overall evidence for current cigarette smoking as a risk factor for incident chronic kidney disease. Further investigation is needed to more carefully examine the strength of the association between cigarette smoking and incident kidney disease.

Prevention of nephropathy in patients with type 2 diabetes mellitus

The rising incidence of type 2 diabetes mellitus and of its complications will make it the most important health care challenge in the first quarter of the 21st Century. Diabetic nephropathy left unchecked will overwhelm the renal resources. Simple methods (proper diet and exercise, prevention of obesity) are successful in preventing type 2 diabetes in the great majority of the persons at risk. In patients with established type 2 diabetes, nephropathy can be prevented or greatly delayed by strict metabolic control, strict control of blood pressure using angiotensin-converting enzyme inhibitors and angiotensin receptor blockers as the first line of drugs, tight control of serum lipids using statins as indicated, low protein diet, avoidance of smoking and other nephrotoxic influences, prevention of abnormalities in calcium/phosphorus metabolism, and prevention of renal anemia by the early use of erythropoietin. Current research offers the promise of definitive prevention of both type 2 diabetes and diabetic nephropathy.

The changing epidemiology of diabetic microangiopathy in type 1 diabetes

Diabetic microvascular complications in the kidney and the eye are a major burden for diabetic patients due to increased morbidity and mortality. Furthermore, diabetic nephropathy is the leading cause of end-stage renal disease and diabetic retinopathy is the leading cause of blindness in younger patients, representing a major public health concern. During the past two decades beneficial effects of, in particular, aggressive antihypertensive control and strict glycaemic control have been demonstrated in randomised controlled clinical trials. Technological improvements in diabetes care have made good metabolic control easier to achieve. Has this led to an improved prognosis? In observational studies from dedicated centres, a decrease from 47 to 13% has been reported in the incidence of proliferative diabetic retinopathy after 20-25 years of diabetes, and the incidence of overt diabetic nephropathy after 20 years has decreased from 28 to 5.8%. Even functional and morphological remission of diabetic nephropathy has been reported. Despite this, recent population-based studies have failed to demonstrate a decrease in the incidence of blindness caused by diabetes, and the incidence of end-stage renal disease has progressively increased. This may, in part, be the result of a combination of increasing numbers of diabetic patients and a lag phase between improvement in management and a decline in end-stage complications. It is of concern, however, that the results from specialised centres may not apply to routine diabetes care. It is, therefore, mandatory that the beneficial effects of pharmacological and non-pharmacological interventions demonstrated in clinical trials and recommended by treatment guidelines are translated into clinical practice to ensure a widespread improvement in prognosis.

Blood pressure and cardiac autonomic function in relation to risk factors and treatment perspectives in Type 1 diabetes

The cumulative incidence of diabetic nephropathy in Type 1 diabetes mellitus is in the order of 25 30%. The recognition that elevated blood pressure (BP) is a major factor in the progression of these patients to end-stage renal failure has led to the widespread use of antihypertensive therapy in order to preserve glomerular filtration rate and ultimately to reduce mortality. The routine measurement of microalbuminuria allows early identification of the subgroup of patients at increased risk of developing clinical nephropathy. Microalbuminuric Type 1 diabetic patients show a number of characteristic pathological abnormalities. In addition to elevated BP and abnormal circadian rhythm, there are also associated abnormalities of vagal function, lipid profile and endothelial function, as well as an increased prevalence of retinopathy. The first section of this two-part review focusses on the early changes associated with renal involvement in Type 1 diabetes. It addresses the associations between urinary albumin excretion, glycaemic control, smoking, BP, circadian BP variation, QT interval abnormalities and autonomic function in three groups of patients; those with normoalbuminuria, those progressing towards microalbuminuria and those with established low-grade microalbuminuria.

Smoking is associated with renal impairment and proteinuria in the normal population: the AusDiab kidney study. Australian Diabetes, Obesity and Lifestyle Study

BACKGROUND

Smoking has been associated with the prevalence, development, and progression of kidney disease. The effect of smoking on kidney function in the healthy population is unclear. We examined the relationship between smoking and indicators of kidney damage in a healthy population without impaired fasting glucose levels, impaired glucose tolerance, diabetes mellitus, or hypertension.

METHODS

This is a randomly selected, population-based, cross-sectional study of 11,247 Australian adults. Smoking status was determined by questionnaire. Subjects were tested for indicators of kidney damage: renal impairment by Cockcroft-Gault-estimated glomerular filtration rate less than 60 mL/min/1.73 m2 and proteinuria by urine protein-creatinine ratio of 0.20 mg/mg or greater.

RESULTS

After adjusting for potential confounding factors, smoking was significantly associated with renal impairment in men with an odds ratio of 3.59, but not in women. Smoking was significantly associated with proteinuria in subjects with high-normal systolic blood pressure, with odds ratios ranging from 3.64 at 131.5 mm Hg to 5.76 at 139.5 mm Hg, and in subjects with high-normal 2-hour glucose levels, with odds ratios ranging from 1.76 at 7.0 mmol/L to 10.84 at 7.7 mmol/L. Lifetime exposure, but not current level of smoking, correlated with lower estimated glomerular filtration rate and greater urine protein-creatinine ratio.

CONCLUSION

Smoking is associated with renal impairment and proteinuria in a population without hypertension or abnormal glucose metabolism. A dose-response relationship was found between cumulative amount of smoking and indicators of kidney damage. In conjunction with other studies and plausible biological mechanisms, this study suggests that smoking may cause kidney damage, even in a healthy population.

Cigarette smoking: an important renal risk factor - far beyond carcinogenesis

In recent years, it has become apparent that smoking has a negative impact on renal function, being one of the most important remediable renal risk factors. It has been clearly shown that the risk for high-normal urinary albumin excretion and microalbuminuria is increased in smoking compared to non-smoking subjects of the general population. Data from the Multiple Risk Factor Intervention Trial (MRFIT) indicate that at least in males, smoking increases the risk to reach end-stage renal failure. Smoking is particularly "nephrotoxic" in older subjects, subjects with essential hypertension and patients with preexisting renal disease. Of interest, the magnitude of the adverse renal effect of smoking seems to be independent of the underlying renal disease. Death-censored renal graft survival is decreased in smokers, indicating that smoking also damages the renal transplant. Cessation of smoking has been show to reduce the rate of progression of renal failure both in patients with renal disease or a renal transplant. The mechanisms of smoking-induced renal damage are only partly understood and comprise acute hemodynamic (e.g., increase in blood pressure and presumably intraglomerular pressure) and chronic effects (e.g., endothelial cell dysfunction). Renal failure per se leads to an increased cardiovascular risk. The latter is further aggravated by smoking. Particularly survival of smokers with diabetes mellitus on hemodialysis is abysmal. In the present review article the current state of knowledge about the renal risks of smoking is reviewed. It is the aim of the article to point out that smoking not only increases the risk of renal cell carcinoma or uroepithelial cell carcinoma, but also the risk of a faster decline of renal function. The latter is a relatively new negative aspect which has not been widely recognized.

Effect of smoking on the prevalence of albuminuria in Japanese men with non-insulin-dependent diabetes mellitus

Smoking is a risk factor for diabetic nephropathy in patients with IDDM and potentially those with NIDDM. We investigated the relationship between renal involvement and cigarette smoking in 148 men with NIDDM. The presence of renal involvement was assessed by determining the overnight urinary albumin/creatinine ratio (mg/g, ACR). The patients were divided into three groups, normo-, micro-, and macroalbuminuria, based on the ACR (< 30, 30-300, and 300 < or = mg/g, respectively). The incidence of micro-/macroalbuminuria in 81 smokers was significantly higher than that in 21 ex-smokers (stopped smoking at least 10 years prior to the study) or 40 non-smokers (53.1, 33.3, and 20.0%, respectively). The prevalence of smoking in the groups of patients with normo-, micro-, and macroalbuminuria were 45, 73, and 76%, respectively. The relative risk (odds ratio) for the prevalence of micro-/macroalbuminuria associated with smoking was 4.5 (95% CI, 1.9-11.6, P < 0.001) in smokers and was 2.0 (not significant) in ex-smokers. Our results indicate that stricter counselling about the importance of quitting smoking will be necessary in patients with NIDDM to protect against the development of diabetic nephropathy.

The acute effect of smoking on systemic haemodynamics, kidney and endothelial functions in insulin-dependent diabetic patients with microalbuminuria

The acute effect of smoking upon arterial blood pressure, urinary albumin excretion rate, glomerular filtration rate and transcapillary escape rate of albumin were investigated in nine normotensive insulin-dependent diabetic patients with microalbuminuria, who had been smoking for 19 (range 4-30) years. In a prospective, open randomized cross-over design, patients were investigated with and without smoking three cigarettes per hour during a 5.5-h period. A rise in systolic blood pressure and heart rate (Takeda TM2420, median (range)) was observed during the smoking day (10(-11 to 14) mmHg and 8 (-1 to 19) beats min-1), compared to the non-smoking day (1 mmHg (-7 to 13) (p = 0.05) and 0 beats min-1 (-2 to 4) (p < 0.01)). Urinary albumin excretion rate (ELISA), glomerular filtration rate (plasma clearance of 51Cr-EDTA) and transcapillary escape rate of albumin (125I-albumin) remained the same with or without smoking. Our study suggests that heavy smoking induces an abrupt rise in systolic blood pressure and heart rate, while vascular leakage of albumin and glomerular filtration rate remain unaltered in normotensive insulin-dependent diabetic patients with microalbuminuria who had been smoking for several years.

Diabetic nephropathy in type II diabetes

The incidence of end-stage renal failure in patients with type II diabetes has dramatically increased in recent years, both in the United States and, with some delay, in some European countries. These epidemiologic observations have thoroughly dispelled the mistaken belief that renal prognosis was benign in type II diabetes. Recent interest has focused on the early stages of nephropathy in type II diabetes. With respect to renal hemodynamics, renal morphology, and progression of established diabetic nephropathy, there are no substantial differences between types I and type II diabetes. There is good evidence that preventive measures are effective, ie, glycemic control, blood pressure control, protein restriction, and discontinuation of smoking. The high prevalence of the disease (which in principle is preventable) calls for intense efforts to (1) educate the medical community, (2) substantially improve patient education and medical care, and (3) intensify research in this field.

Clinical factors associated with urinary albumin excretion in type II diabetes

Clinical factors associated with urinary albumin excretion (UAE) in type II diabetes are less well known than in type I diabetes. To examine the factors associated with UAE in type II diabetes, 933 Appropriate Blood Pressure Control in Diabetes Trial patients were classified according to UAE status: normoalbuminuria (< 20 micrograms/min), microalbuminuria (20 to 200 micrograms/min), and macroalbuminuria (> 200 micrograms/min). The class of UAE was then correlated with various clinical factors. Using univariate analyses, Hispanic ethnicity, African-American race, male gender, poor glycemic control, insulin use, long duration of diabetes, dyslipidemia, diastolic and systolic hypertension, smoking, and obesity were significantly correlated with microalbuminuria and macroalbuminuria. Using multivariate logistic regression analyses controlling for diabetes duration, glycosylated hemoglobin, gender, and race, the most significant predictors of microalbuminuria and macroalbuminuria were systolic hypertension, body mass index, high-density lipoprotein cholesterol, insulin use, and smoking pack-years. Of these factors, several are potentially reversible with aggressive intervention.

Night blood pressure and cigarette smoking: disparate association in healthy subjects and diabetic patients

Cigarette smoking and diabetes are well known risk factors for cardiovascular disease. The relation of nocturnal blood pressure (BP) to cigarette smoking is unclarified. We examined ambulatory BP in 18 healthy smokers matched for sex and age to 18 non-smokers. Sixteen smoking type 1 diabetic patients matching 16 non-smoking patients with normal urinary albumin excretion were also investigated. None of the healthy subjects or diabetic patients had a clinic BP > 160/95 mmHg. Night BP (systolic/diastolic mmHg) in healthy smokers (mean +/- SD) 102 +/- 9/57 +/- 5 was lower than in healthy non-smokers 108 +/- 10/61 +/- 6 (p = 0.06/p < 0.05). The difference between smokers and non-smokers was most prominent in the 3 h period just before rising (99 +/- 9/57 +/- 6 versus 108 +/- 8/62 +/- 7, p < 0.01/p < 0.05). Daytime BP was similar between groups. The night/day ratio (%) of systolic (84 +/- 7) and diastolic (74 +/- 7) BP in healthy smokers was lower than in non-smokers (88 +/- 5 versus 80 +/- 5, p < 0.05 and p < 0.01) indicating an altered diurnal rhythm of blood pressure. No statistical significant difference was found for night or day BP in diabetic smokers versus non-smokers. The finding of a significantly lower BP in healthy (supine) smokers at night speaks against dysautonomia explaining the lower clinic BP found in epidemiological studies, as recently proposed. Alternatively a rebound effect or the existence of a substance with vasodilating properties in non-diabetic smokers is suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria in normals and essential hypertension

The prevalence and determinants of urinary albumin excretion rate (AER) were assessed in lean and overweight normotensive subjects (NT) and patients with essential hypertension (EH). In NT and EH, the presence of overweight was associated with a significant exacerbation of AER. In the normotensive population, AER was higher in subjects with a positive family history of hypertension. An important role for smoking was observed in the hypertensive population; in fact, the prevalence of microalbuminuria (MA) was almost twofold in lean hypertensive smokers when compared to nonsmokers. Among other determinants of AER, a major influence of systolic arterial pressure, urinary excretion of urea (an estimate of protein intake), and high-density lipoprotein (HDL) cholesterol (inversely correlated with AER) was observed mainly in lean EH patients. The significance of microalbuminuria is unclear. Is it a marker of cardiovascular risk and/or a predictor of the future development of renal disease in EH?

Implementation of a structured care programme for diabetes mellitus in a defined population in mid-Sweden

A local programme for diabetes care, based on the Swedish national programme, was introduced in the Köping-Arboga-Kungsör area in mid-Sweden in 1984. Before the programme was implemented, a survey of diabetes care was performed in the area. Two years later, a new survey involving 92% of 1253 diabetes patients in the area was performed to see if the programme was associated with an improved level of care, more optimal treatment and better metabolic control. A significant number of Type 2 patients were referred from hospital outpatient clinics to the primary health care centres. The proportion of patients on diet only increased from 26% to 30% and the average number of daily injections among insulin-treated patients increased. The average number of check-ups by a doctor decreased and the number of check-ups by specially trained nurses increased. Overall, the number of check-ups per year increased from 3.1 to 3.8. The proportion of the patients fulfilling the HbA1c criterion of 'good metabolic control' (< or = 6.0%) increased significantly, as did those fulfilling the fasting blood glucose criterion (< or = 7.0 mmol l-1). Serum cholesterol and serum triglyceride levels increased. Relative weight, blood pressure, smoking habits, and exercise habits were unchanged. In conclusion, the quality of diabetes care was improved after the diabetes care programme was implemented.

Cigarette smoking and diabetes: an update

The article provides an overview of recent scientific information on the role of cigarette smoking in the prognosis of diabetes. Data sources included an English-language MEDLINE search for 1989 through 6/1993, supplemented by manual search of bibliographies of pertinent articles. Only studies of humans were considered. Cigarette smoking is related to the development and progression of diabetic nephropathy. Therefore, smoking status has to be taken into account in clinical studies on the course of nephropathy. The association between smoking and retinopathy is less consistent. Evidence is accumulating that cigarette smoking influences insulin action. Several large prospective cohort studies have shown that the relative risk for all-cause mortality is about twice as high for smoking compared to non-smoking diabetic patients. Strong associations are consistently found between cigarette-pack years and complications. It has been calculated that the theoretical benefit of stopping smoking is the most (cost-)effective risk factor intervention for diabetic patients. However, available programmes to help diabetic patients to stop smoking are unsuccessful.

Smoking attenuates the vasoconstrictor response to noradrenaline in type I diabetic patients and normal subjects: possible relevance to diabetic nephropathy

Exaggerated vascular reactivity has been implicated in the pathogenesis of diabetic nephropathy, and several studies suggest that smoking accelerates its progression. We therefore assessed the vasoactive effects of smoking by comparing noradrenaline-induced vasoconstriction in dorsal hand-veins between smoking and non-smoking groups of Type I diabetic patients with and without microalbuminuria and in non-diabetic subjects. Smokers had a significantly higher dose causing 50% vasoconstriction (reduced sensitivity to noradrenaline) in all three groups: microalbuminuric diabetic smokers vs. nonsmokers, 20.2(4.6) (SEM) vs. 6.6(2.3) ng min-1 (P = 0.02); normoalbuminuric, 76.9(29.4) vs. 22.8(9.1) ng min-1 (P = 0.03); non-diabetic subjects, 97.8(30.0) vs. 38.0(12.8) ng min-1 (P = 0.01). Both microalbuminuric diabetic groups showed significantly greater sensitivity to noradrenaline-induced vasoconstriction than the other smoking and non-smoking groups, respectively (P < 0.01). Vasoconstrictors responses to noradrenaline are attenuated in smokers, possibly due to alpha-adrenoceptor down-regulation. Smoking could increase urinary albumin losses and accelerate renal damage through catecholamine surges which raise systemic and, perhaps, intraglomerular blood pressure. This hypothesis deserves further consideration.

Cigarette smoking and urinary albumin excretion in insulin-treated diabetics without manifest nephropathy

The frequency of microalbuminuria and glomerular hyperfiltration in insulin-treated diabetics without manifest nephropathy was studied in 76 patients, 20-40 years of age and with a diabetes duration not exceeding 20 years. Clinical determinants of urinary albumin excretion (UAE) with regard to smoking were studied further in a sample of male diabetics (n = 49) without manifest nephropathy. All patients had an age-related glomerular filtration rate (GFR) exceeding -2 SD, and their diastolic blood pressure (DBP) did not exceed 90 mmHg. GFR was assessed by 51Cr-EDTA-clearance, and UAE was analysed using an immunochemical method. Diabetic smokers with a long diabetes duration (10-20 years) had a significantly higher UAE (39.5 +/- 2.4 mg 24 h-1 vs. 17.1 +/- 2.4 mg 24 h-1; P = 0.03), a higher mean arterial blood pressure (MAP) (97.9 +/- 7.5 mmHg vs. 91.5 +/- 6.3 mmHg; P = 0.02) and a higher frequency of micro-albuminuria (85.7% vs. 37%; P = 0.028) than non-smoking diabetics. Smokers with a short diabetes duration (0-10 years) had a significantly higher frequency of glomerular hyperfiltration (64% vs. 15%; P = 0.005) than non-smokers. The frequency of microalbuminuria or blood pressure did not differ significantly. In male non-smokers (n = 35) UAE was positively correlated with HbAlc and negatively correlated with age of onset. In male smokers (n = 14) regression analysis showed that UAE was positively correlated only with duration of smoking. We conclude that smoking is associated with two accepted risk factors for nephropathy in insulin-treated diabetics, namely hyperfiltration and microalbuminuria. A positive linear relationship between smoking parameters and UAE in male diabetics also supports the view that smoking may increase the risk of nephropathy development in insulin-treated diabetics.

A study of patients with diabetes mellitus (type 1) and end-stage renal failure: tobacco usage may increase risk of nephropathy and death

Thirty-four consecutive patients with diabetes mellitus as a plausible cause of end-stage renal failure were investigated with regard to outcome and tobacco consumption. The mean duration of diabetes was 25.5 years. Thirty-one of the patients had used tobacco regularly for at least 5 years. For 28 patients it was possible to calculate the intake of tobacco as the daily mean and the total consumption (expressed as pack years). The time period (in years) between initiation of tobacco usage and onset of persistent proteinuria, as an early indicator of diabetic nephropathy, was shorter if the daily consumption of tobacco was higher (P less than 0.01) and the total consumption (pack years) in these patients was lower (P less than 0.05). There was an increased risk of early death (P less than 0.01) in patients who were currently smokers when they were uraemic (predialysis), on dialysis or had kidney grafts, compared to those who had never used tobacco or who were ex-smokers. In conclusion, it appears to be important for insulin-dependent diabetic patients to avoid tobacco usage and for current smokers to give up the habit in order to reduce the risk of diabetic nephropathy and early death.

Smoking and metabolic control in patients with insulin-dependent diabetes mellitus

Within a defined geographical area, all 192 subjects with insulin-dependent diabetes of at least 2 years duration and free of diabetic complications were identified; 60 (31%) were smokers. The prevalence of smoking increased significantly with increasing haemoglobin A1c levels (17.5% among subjects with the best metabolic control, 47.5% in those with the worst control). Smoking and non-smoking diabetic patients did not differ in attitudes towards the disease, psychological well-being, extent of tedium, frequency of self-controls of blood glucose or proportion of patients with any sick leave in the preceding 2 years. In a case referent study of 25 matched patients with good or poor metabolic control, exposure to smoking was significantly more common among those with poor control (odds ratio 6.0). Thus there are several lines of evidence that smoking is associated with impaired metabolic control in patients with diabetes.

Smoking and diabetes

The frequency of smoking in diabetic patients is not appreciably different from that in the general population. As in non-diabetic subjects, smoking is a major cardiovascular risk factor in diabetic patients. For young diabetic patients, smoking has been identified as a risk for macroproteinuric nephropathy. In respect of retinopathy, study results are more controversial. Recent studies also suggest smoking as a risk indicator for extra-articular connective tissue changes and neuropathy. Patients who already present with vascular complications, pregnant women, and women who use oral contraceptive drugs appear to run a particularly high risk by smoking. Stopping smoking reduces the risk of vascular morbidity and mortality in non-diabetic subjects. Although no comparable studies are available for diabetic populations, it should be assumed that the beneficial effects of stopping smoking are applicable to diabetic patients as well. Programmes to encourage diabetic patients to stop smoking are scarce and have not been successful.

Microalbuminuria in diabetes: relationships between urinary albumin excretion and diabetes-related variables

A single observer reviewed 842 of the 917 known diabetic patients registered with 40 GPs in the Poole area. Fifty-nine per cent (493) of those reviewed submitted a timed overnight urine collection to measure albumin excretion rate (AER) and overnight albumin/creatinine ratio (ON-Alb/Creat); 43 samples were excluded because of urinary tract infection and/or proteinuria. A random urine sample was obtained in 607 diabetic patients to measure the random albumin/creatinine ratio (R-Alb/Creat); 68 specimens were excluded because of infection and/or proteinuria, and in a further 10 samples urinary creatinine was not measured. Stepwise multiple regression analyses found significant associations with the following variables: for AER, blood glucose (p = 0.001), smoking category (p = 0.002), sex (p = 0.034), and systolic blood pressure (p = 0.035); for R-Alb/Creat, blood glucose (p = 0.001), retinopathy (p = 0.004), systolic blood pressure (p = 0.004), diastolic blood pressure (p = 0.015), coronary artery disease (p = 0.02), sex (p = 0.034), and vibration sense (p = 0.038). Interestingly, glycosylated haemoglobin was not a significant determinant of albuminuria in either analysis.

The prevalence of proteinuria detected by Albustix in a defined diabetic population

All the known diabetic patients (917) from a defined population (90,660) were called for review by a single observer. A total of 842 (92%) attended and proteinuria, identified using Albustix (0.3 g/l or more), was found in 57 cases (6.8%), but in 9 this was in association with a urinary tract infection. Diastolic blood pressure, an ulcerated or amputated lower limb, and smoking category were found to be the only significant predictors of proteinuria after a multiple logistic regression analysis. A serum creatinine greater than 150 mumol/l was found in 29 (3.8%) of the 768 diabetics in whom it was measured. However, proteinuria was only present in 7 of the diabetics with impaired renal function. In those aged less than 65 years, the prevalence of proteinuria with impaired renal function was 0.75%.

Cigarette-smoking as a risk factor for macroproteinuria and proliferative retinopathy in type 1 (insulin-dependent) diabetes

In a case control study 192 cigarette-smoking patients with Type 1 (insulin-dependent) diabetes were compared with 192 non-cigarette-smoking patients pair-matched for sex (90 females), duration of diabetes (mean 14 years), and age (mean 32 years). Macroproteinuria was found in 19.3% of the smoking and in 8.3% of the non-smoking patients (p less than 0.001). Proliferative retinopathy was present in 12.5% of the smoking and in 6.8% of the non-smoking patients (p less than 0.025). The percentages of patients with normal proteinuria or without retinopathy were comparable between the two groups. In addition, glycosylated haemoglobin values and the prevalence of hypertension were similar between smoking and non-smoking patients. Thus, cigarette-smoking appears to be a risk factor for the progression of incipient to overt nephropathy and of background to proliferative retinopathy in Type 1 diabetes.