Table 1 Variable coding

Eligibility and Exposure

Now thinking about your mental health, which includes stress, depression, and problems with emotions, for how many days during the past 30 days was your mental health not good?

• Number of days 0–30

• Don't know/ not sure/ refused

• Those answering 0 were placed in a "none" category

• Those answering 1–30 were placed in categories based on quartiles of answers, where quartile 1 (Q1) was 1–2 days, Q2 was 3–6 days, Q3 was 7–14 days, and Q4 was 15–30 days

• Unknowns were removed

Eligibility and Outcome

Including all types of dentists, such as orthodontists, oral surgeons, and all other dental specialists, as well as dental hygienists, how long has it been since you last visited a dentist or a dental clinic for any reason?

• Within the past year (anytime less than 12 months ago)

• Within the past 2 years (1 year but less than 2 years ago)

• Within the past 5 years (2 years but less than 5 years ago)

• 5 or more years ago or never

• "Within the past year" considered up-to-date on dental care

• Unknowns were removed

Eligibility and Outcome

Not including teeth lost for injury or orthodontics, how many of your permanent teeth have been removed because of tooth decay or gum disease?

• None

• 1 to 5

• 6 or more (but not all)

• All

• "6 or more (but not all)" and "all" combined as outcome for tooth loss

• Unknowns were removed

Eligibility and Confounder

Are you male or female?

• Male

• Female

• Must answer one of these two answers at beginning of survey to be eligible to continue

• In regression analysis "male" (yes = 1) was used as an indicator variable

Confounder

BRFSS-derived age group variable

• 18 to 24

• 25 to 34

• 35 to 44

• 45 to 54

• 55 to 64

• 65 and older

No unknowns were present in native dataset

In regression analysis, each level was modeled as an indicator variable with the lowest age group as reference

Confounder

BRFSS-derived Hispanic status variable

• Yes

• No

• Unknown

Indicator variable coded as Yes = 1 (with comparison "no" and "unknown") was used in regression analysis

Confounder

Recode of BRFSS-derived race variable

• White only

• Black or African American only

• American Indian or Alaskan native only

• Asian only

• Native Hawaiian or other Pacific Islander only

• Other race

• Unknown

"Other race" includes "other race only" and "multiracial"

For regression analyses, "White only" and "unknown" were combined into the comparison group, and three indicator variables were developed:

• "Black or African American only" (yes = 1)

• "Asian only" (yes = 1),

• any of the other races listed as an "other race" flag (yes = 1)

Confounder

Recode of BRFSS-derived marital status variable

• Coupled

• Formerly married

• Never married

• Unknown

"Coupled" includes married and unmarried couples

"Formerly married" includes divorced and widowed

For regression, indicator variables were made for "never married" (yes = 1) and "formerly married" (yes = 1), with "coupled" and "unknown" combined in the comparison group

Eligibility and Confounder

What is the highest grade or year of school you completed?

• Less than high school graduate

• High school graduate

• Some college

• College graduate

Unknowns were removed

"Less than high school" includes respondents who never attended school, only attended kindergarten, or achieved grades up to 11

"High school graduate" includes grade 12 and GED

"Some college" includes college or technical school one to three years

"College graduate" includes college four years or more

For regression analysis, a combined indicator variable for "less than high school graduate" and "high school graduate" (yes to either = 1) was created, and an indicator variable for "some college" (yes = 1), with the comparison group "college graduate"

Confounder

Is your annual household income from all sources:

• < $10,000

• $10,000 to < $15,000

• $15,000 to < $20,000

• $20,000 to < $25,000

• $25,000 to < $35,000

• $35,000 to < $50,000

• $50,000 to < $75,000

• $75,000 or more

• Unknown

For regression analysis, "$75,000 or more" and "unknown" were combined for the comparison group, and indicator variables were made for each of the other levels where yes = 1 if the respondent reported that level

Confounder

Has a doctor, nurse, or other health professional ever told you that you had any of the following?

Asked about the following conditions:

• Asthma

• heart attack or myocardial infarction (MI)

• angina or coronary heart disease (CHD)

• stroke

• skin cancer

• other type of cancer

• chronic obstructive pulmonary disease (COPD), emphysema, or chronic bronchitis

• some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia

• depressive disorder

• kidney disease

• diabetes

For regression analysis, indicator variables were made for each reported co-morbidity where yes = 1, with all others in the comparison group

Eligibility and Confounder

Would you say that in general your health is–-

• Excellent

• Very good

• Good

• Fair

• Poor

Unknowns were removed

For regression analysis, indicator variables were made for "fair" (yes = 1) and "poor" (yes = 1) with the comparison group including all other levels

Confounder

During the past 30 days, how many days per week or per month did you have at least one drink of any alcoholic beverage such as beer, wine, a malt beverage or liquor?

0 through 30. Those who answered 1 through 30 were classified as having an alcoholic drink within the last 30 days

For regression analysis, an indicator variable was made for having at least one alcoholic drink in the last 30 days (yes = 1), with all other records in the comparison group

Confounder

Have you smoked at least 100 cigarettes in your entire life? and

Do you now smoke cigarettes every day, some days, or not at all?

To be classified as a current tobacco smoker, respondent must have said "yes" to smoking at least 100 cigarettes in their entire life, and either saying they currently smoke some days or every day

For regression analysis, current smoking status (1 = "yes") was used as an indicator variable, with all other records in the comparison group

Confounder

Do you currently use chewing tobacco, snuff, or snus every day, some days, or not at all?

• Yes

• No

For regression analysis, an indicator variable for oral tobacco user (yes = 1) was created with all other levels as comparison group

Confounder

Do you have any kind of health care coverage, including health insurance, prepaid plans such as HMOs, or government plans such as Medicare, or Indian Health Service?

• Yes

• No

For regression analysis, an indicator variable was made to indicate the lack of plan (not having plan = 1), with the comparison group reporting having a plan

Confounder

BRFSS-derived classification of body mass index (BMI)

• Underweight

• Normal

• Overweight

• Obese

• Unknown

For regression analysis, "normal" was combined with "unknown" for the comparison group, and indicator variables were developed for underweight (yes = 1), overweight (yes = 1), and obese (yes = 1)

Confounder

During the past month, other than your regular job, did you participate in any physical activities or exercises such as running, calisthenics, golf, gardening, or walking for exercise?

• Yes

• No

For regression analysis, and indicator variable was made to indicate lack of exercise in the past 30 days (not exercising = 1), with those reporting exercise as the comparison group