Diet and Tobacco Use: Analysis of Data From the Diabetic Control and Complications Trial, a Randomized Study

David K. Cundiff

Disclosures
In This Article

Subjects and Methods

The DCCT eligibility criteria and screening methods have been reported in detail.[30,31,32,33,34] At baseline, all subjects had to be between 13 and 39 years of age, C peptide-deficient, and in good general health. Subjects who were recruited for the primary prevention study were required to have had insulin-dependent diabetes mellitus for at least 1 year but for less than 5 years, no evidence of retinopathy on stereoscopic fundus photographs, less than 40 mg/24 hours of urinary albumin excretion, and no hypertension. Patients enrolled in the secondary intervention study had background diabetic retinopathy (>=1 microaneurysm in either eye but less than stage P2 according to the Diabetic Retinopathy Study).[32,35] The duration of their diabetes ranged from 1 to 15 years and they could have a urinary albumin excretion as high as 200 mg/24 hours.

A total of 1441 study participants were recruited between 1983 and 1989, including 726 subjects in the primary prevention study and 715 in the secondary intervention study. The baseline characteristics of the study subjects have been published previously.[33] The range of follow-up for all subjects was 4 to 9.5 years. At the end of the trial in 1993, the mean follow-up was 6.5 years.[36]

With the assistance of registered dietitians trained in collecting nutrient consumption data, all 1441 subjects submitted detailed diet histories (ie, 1-week recall) upon entry into the study. Subsequently, the dietitians obtained follow-up diet histories at years 2, 4, and at the end of the study.[30,31] By analyzing these diet histories with nutritional component software, the dietitians and statisticians generated a data set consisting of each subject's consumption of 99 macro and micronutrients at baseline and while on study. After screening all of the nutrients considered in the DCCT, the following were analyzed in this study:

  1. Calories

  2. Protein

  3. Total carbohydrates

  4. Starch

  5. Refined carbohydrates (ie, sucrose, glucose, lactose, fructose, and galactose)

  6. Total fats

  7. Percentage total fat

  8. Saturated fats

  9. Percentage saturated fats

  10. Monounsaturated fats

  11. Polyunsaturated fats

  12. Cholesterol

  13. Alcohol

  14. Fiber

  15. Sodium

The baseline history and physical form included the following tobacco use questions:

  1. Has the patient ever smoked cigarettes or cigarillos daily?

  2. Does the patient now smoke cigarettes or cigarillos?

  3. On the average, how many cigarettes or cigarillos a day does the patient now smoke?

    1. How long has it been since the patient quit cigarettes or cigarillos?

    2. If the patient has never quit, check here.

  4. At what age did the patient first become a daily cigarette or cigarillo smoker?

  5. For how many months (or years) altogether has the patient quit cigarettes and cigarillos since he/she first started?

  6. On the average, how many cigarettes or cigarillos a day did the patient smoke during the period in his/her life when he/she was tobacco using the heaviest?

  7. Has the patient ever smoked pipes or cigars daily?

  8. Does the patient now smoke pipes or cigars?

  9. On the average, how many pipefuls or cigars a week does the patient now smoke?

    1. How long has it been since the patient last quit tobacco using pipes or cigars?

    2. If the patient has never quit, check here.

  10. At what age did the patient first become a daily pipe or cigar smoker?

  11. For how many months (or years) altogether has the patient quit tobacco using pipes and cigars since he/she first started?

  12. On the average, how many pipefuls or cigars a week did the patient smoke during the period in his/her life when he/she smoked the heaviest?

Most tobacco users smoked cigarettes or cigarillos (ie, 98% to 100% of females and 92% to 93% of males). Consequently, the variable "tobacco use" used in this article is almost synonymous with cigarette or cigarillo smoking.

The yearly and closeout history and physical exam included nearly identical follow-up tobacco using-related questions.

The HbA1c serum determinations (obtained at least once every 3 months), BMIs, and serum lipid profiles (done yearly), were compared with the nutrient intake and tobacco use status.

The nutritional data and serum lipid determinations from baseline, 2 years, and 4 years into the trial were adjusted for age and sex. The adjusted values were derived from a regression equation plotting the variables against age and finding the means and slopes of the variables.[37]

Using the baseline calories for a female as an example, the equation for the adjustment was the following: adjusted baseline calories = baseline calories * 1945/(1945 +(26.2-age) * 9.52)

The average females consumed 1945 calories per day and began the trial at age 26.2 years. With each additional year, the average female ate 9.52 less calories per day.

For the percent of calories as saturated fat and the serum triglycerides, the relationship of age (roughly in quartiles) at study entry with the smoking or nonsmoking status gave an example of the strengths of the relationships according to age. Since this analysis was not planned by the original DCCT investigators, the Spearman correlation function (a more robust test than the Pearson correlation test)[37] was used to assess the positive or negative association of tobacco use with nutrient intake, BMI, HbA1c, and serum lipids (Tables 1-5).

SAS statistical software performed the data analysis.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.

processing....