Frequencies and percentages for demographic characteristics, health risks, health conditions, and HRQOL indicators appear in Table . Overall, 14.85% had fair or poor general health. Results for the other 8 indicators based on the criterion of 14 or more days of poor health in the past month were as follows: 6.75% had activity limitations due to a physical or mental health problem; 10.55% had poor physical health; 9.7% had pain related activity limitations; 28.8% reported lack of energy; 23.8% reported inadequate sleep or rest; 13.2% were worried, tense or anxious; 10.5% had poor mental health; and 8.2% were sad, blue or depressed.
Percentage for selected demographics, risk factors, health conditions, and HRQOL indicators among Rhode Island adults, 2004†
Patterns of HRQOL
During the first stage of analysis, conventional latent class models, ignoring covariates, were fit to the HRQOL indicator data, demographics and health risks, starting with a 1-class model, and progressing to a model with four classes of HRQOL. The analysis indicated that the four-class model is the better model. During the second stage of analysis, when covariates were included in the models, the four-class LCR model with 12 covariates was selected as it had the lowest BIC score. The four latent classes are characterized as follows: Class 1 is characterized by physically and mentally good HRQOL; Class 2 was characterized as having physically related poor HRQOL; Class 3 was characterized as having mentally related poor HRQOL; and Class 4 as having both physically and mentally related poor HRQOL.
Table presents estimates of (1) the marginal probability (proportion) of each of the 4 latent classes and (2) the conditional probabilities of each indicator for each latent class. RI adults in latent Class 1 (referred to as "healthy people"), accounted for 76% of the population; latent Class 2 (referred to as "physically unhealthy people"), comprised 9%; latent Class 3 ("mentally unhealthy people"), comprised 11%; and latent Class 4 ("both mentally and physically unhealthy people"), comprised 4% (see Table ).
Estimated parameters for the 4-class model
Healthy people (class 1) have low probabilities (less than 17%) for each of the indicators of poor HRQOL. Conversely, both physically and mentally unhealthy people (class 4) have large probabilities (larger than 63%) for each of the poor HRQOL indicators. Physically unhealthy people (class 2) have high probabilities for the physical health indicators and low probabilities for the mental health indicators, while mentally unhealthy people (class 3) have low probabilities for the physical health indicators and high probabilities for the mental health indicators (see Table ).
Figure is a diagrammatic representation of RI adults in latent classes 1–4. It visually demonstrates the unique divergence between Classes 2 and 3 and the magnitude of the difference between Classes 1 and 4.
Latent class membership of Rhode Island adults in relation to HRQOL indicators.
Predictors regressed on classes of HRQOL
The LCR model was used to determine which variables are significant predictors of latent class membership, when adjusting for all other variables in the model. Odds ratios are presented in Table with latent Class 1 (healthy people) treated as the reference group.
Demographic characteristics and risk factors regressed on three classes of HRQOL†
Statistically significant results occur for each of the three latent classes for sex, current asthma, and disability. In general, women, people with asthma, and people with disability have greater odds of poor HRQOL in each Class than men, people without asthma, and non-disabled people. Disability is a highly relevant health condition for poor HRQOL. People with disability have exceptionally high odds ratios for each class of poor HRQOL, e.g. Class 2 OR = 21.43, Class 3 OR = 3.34, Class 4 OR = 19.16.
Being unable to work, unemployed, having no leisure time physical activity, and having diabetes were associated significantly with Classes 2 and 4. They predicted poor physical HRQOL among RI adults.
Current smokers were 1.93 times more likely to be mentally unhealthy than non-smokers, and 3.26 times more likely to be both physically and mentally unhealthy.
Table shows that older age has a significantly increased association with membership in Class 2 (OR = 1.75 for 45–64 years and OR = 2.39 for 65+ years). On the other hand, increased age is related inversely to membership in Class 3 (OR = 0.72 for 45–64 year and OR = 0.22 for 65+ years).
The lowest income category was associated significantly with Class 4 (being both physically and mentally unhealthy) (OR = 3.67). There were no significant relationships observed for race/ethnicity, chronic drinking, or obesity.
To summarize: Class 2 was associated significantly with older age, being female, unable to work, disabled, or unemployed, having no leisure time physical activity, or having asthma or diabetes. Class 3 was associated with being female, being disabled, current smoking, or having asthma. Class 4 combined almost all the predictors of both Classes 2 and 3, e.g. being female, unable to work, disabled or unemployed, current smoking, having no leisure time physical activity, having asthma or diabetes, or having very low household income.