Measurement error of self-reported physical activity levels in New York City: assessment and correction.

Because it is difficult to objectively measure population-level physical activity levels, self-reported measures have been used as a surveillance tool. However, little is known about their validity in populations living in dense urban areas. We aimed to assess the validity of self-reported physical activity data against accelerometer-based measurements among adults living in New York City and to apply a practical tool to adjust for measurement error in complex sample data using a regression calibration method. We used 2 components of data: 1) dual-frame random digit dialing telephone survey data from 3,806 adults in 2010-2011 and 2) accelerometer data from a subsample of 679 survey participants. Self-reported physical activity levels were measured using a version of the Global Physical Activity Questionnaire, whereas data on weekly moderate-equivalent minutes of activity were collected using accelerometers. Two self-reported health measures (obesity and diabetes) were included as outcomes. Participants with higher accelerometer values were more likely to underreport the actual levels. (Accelerometer values were considered to be the reference values.) After correcting for measurement errors, we found that associations between outcomes and physical activity levels were substantially deattenuated. Despite difficulties in accurately monitoring physical activity levels in dense urban areas using self-reported data, our findings show the importance of performing a well-designed validation study because it allows for understanding and correcting measurement errors.

Perceptions and the role of group exercise among New York City adults, 2010-2011: an examination of interpersonal factors and leisure-time physical activity.

OBJECTIVE: To examine associations of descriptive norms (i.e., behaviors of social group members) and exercising 'with a partner' or 'as a part of a group' on weekly leisure-time physical activity. METHODS: T-tests and adjusted multivariable linear models were used to test the associations between descriptive norms and exercising with a partner or as a part of a group with self-reported leisure-time physical activity using the cross-sectional, population-based New York City Physical Activity and Transit (PAT) Survey 2010-2011 (n=3806). RESULTS: Overall, 70.6% of adult New Yorkers reported having physically active friends. Having active friends was associated with increased leisure-time physical activity; however, the effect varied by sex. Compared to those who did not have active friends, males with active friends reported two times more activity (56 min/week) and women reported two and a half times more activity (35 min/week) (both p-values<0.001). Physically active males and females who usually engaged in leisure-time activities as a part of a group reported 1.4 times more activity than those who exercised alone (both p-values<0.03). CONCLUSIONS: Descriptive norms and group exercise were associated with leisure-time physical activity among adults. Based on these associations, encouraging group exercise may be an effective strategy for increasing leisure-time physical activity among certain subgroups.

Self-reported sitting time in New York City adults, the Physical Activity and Transit Survey, 2010-2011.

INTRODUCTION: Recent studies have demonstrated the negative health consequences associated with extended sitting time, including metabolic disturbances and decreased life expectancy. The objectives of this study were to characterize sitting time in an urban adult population and assess the validity of a 2-question method of self-reported sitting time. METHODS: The New York City Health Department conducted the 2010-2011 Physical Activity and Transit Survey (N = 3,597); a subset of participants wore accelerometers for 1 week (n = 667). Self-reported sitting time was assessed from 2 questions on time spent sitting (daytime and evening hours). Sedentary time was defined as accelerometer minutes with less than 100 counts on valid days. Descriptive statistics were used to estimate the prevalence of sitting time by demographic characteristics. Validity of sitting time with accelerometer-measured sedentary time was assessed using Spearman's correlation and Bland-Altman techniques. All data were weighted to be representative of the New York City adult population based on the 2006-2008 American Community Survey. RESULTS: Mean daily self-reported sitting time was 423 minutes; mean accelerometer-measured sedentary time was 490 minutes per day (r = 0.32, P < .001). The mean difference was 49 minutes per day (limits of agreement: -441 to 343). Sitting time was higher in respondents at lower poverty and higher education levels and lower in Hispanics and people who were foreign-born. CONCLUSION: Participants of higher socioeconomic status, who are not typically the focus of health disparities-related research, had the highest sitting times; Hispanics had the lowest levels. Sitting time may be accurately assessed by self-report with the 2-question method for population surveillance but may be limited in accurately characterizing individual-level behavior.

Sodium intake in a cross-sectional, representative sample of New York City adults.

OBJECTIVES: We estimated sodium intake, which is associated with elevated blood pressure, a major risk factor for cardiovascular disease, and assessed its association with related variables among New York City adults. METHODS: In 2010 we conducted a cross-sectional, population-based survey of 1656 adults, the Heart Follow-Up Study, that collected self-reported health information, measured blood pressure, and obtained sodium, potassium, and creatinine values from 24-hour urine collections. RESULTS: Mean daily sodium intake was 3239 milligrams per day; 81% of participants exceeded their recommended limit. Sodium intake was higher in non-Hispanic Blacks (3477 mg/d) and Hispanics (3395 mg/d) than in non-Hispanic Whites (3066 mg/d; both P < .05). Higher sodium intake was associated with higher blood pressure in adjusted models, and this association varied by race/ethnicity. CONCLUSIONS: Higher sodium intake among non-Hispanic Blacks and Hispanics than among Whites was not previously documented in population surveys relying on self-report. These results demonstrate the feasibility of 24-hour urine collection for the purposes of research, surveillance, and program evaluation.

Accelerometer and Survey Data on Patterns of Physical Inactivity in New York City and the United States.

OBJECTIVE: Inactive lifestyles contribute to health problems and premature death and are influenced by the physical environment. The primary objective of this study was to quantify patterns of physical inactivity in New York City and the United States by combining data from surveys and accelerometers. METHODS: We used Poisson regression models and self-reported survey data on physical activity and other demographic characteristics to predict accelerometer-measured inactivity in New York City and the United States among adults aged ≥18. National data came from the 2003-2004 and 2005-2006 National Health and Nutrition Examination Surveys. New York City data came from the 2010-2011 New York City Physical Activity and Transit survey. RESULTS: Self-reported survey data indicated no significant differences in inactivity between New York City and the United States, but accelerometer data showed that 53.1% of persons nationally, compared with 23.4% in New York City, were inactive ( P < .001). New Yorkers reported a median of 139 weekly minutes of transportation activity, compared with 0 minutes nationally. Nationally, 50.0% of self-reported activity minutes came from recreation activity, compared with 17.5% in New York City. Regression models indicated differences in the association between self-reported minutes of transportation and recreation and accelerometer-measured inactivity in the 2 settings. CONCLUSIONS: The prevalence of physical inactivity was higher nationally than in New York City. The largest difference was in walking behavior indicated by self-reported transportation activity. The study demonstrated the feasibility of combining accelerometer and survey measurement and that walkable environments promote an active lifestyle.

Obesity and diabetes in New York City, 2002 and 2004.

INTRODUCTION: Obesity and diabetes have increased rapidly nationwide, yet reliable information on these disease trends in local urban settings is unavailable. We undertook this study to characterize trends in obesity and diagnosed diabetes from 2002 to 2004 among white, black, and Hispanic adult residents of New York City. METHODS: We used data from the Community Health Survey, an annual random-digit-dial telephone survey of approximately 10,000 New York City adults aged 18 years or older, and from the Behavioral Risk Factor Surveillance System, a similar nationwide survey. Main outcome measures were body mass index (BMI), calculated from self-reported height and weight, and self-reported diabetes. RESULTS: In 2 years, the prevalence of obesity increased 17% in New York City, from 19.5% in 2002 to 22.8% in 2004 (P < .0001). The prevalence of diagnosed diabetes also increased 17%, from 8.1% in 2002 to 9.5% in 2004 (P < .01). Nationally, the prevalence of obesity increased by 6% during this same time period (P < .05), and diabetes prevalence did not increase significantly. The median BMI among white adults in New York City was 25.1 kg/m(2), significantly lower than among Hispanics (26.4 kg/m(2)) and blacks (26.6 kg/m(2), P < .05). The prevalence of diabetes increased across all BMI categories. DISCUSSION: The rapid increase in obesity and diabetes in New York City suggests the severity of these twin epidemics and the importance of collecting and analyzing local data for local programming and policy making.

Validation of self-rated overall diet quality by Healthy Eating Index-2010 score among New York City adults, 2013.

OBJECTIVE: Chronic conditions such as cardiovascular disease and cancer can result from a number of diet-related environmental and behavioral factors. Screening for poor diet is helpful in developing interventions to prevent chronic disease, but measuring dietary behavior can be costly and time-consuming. The purpose of this study was to test the ability of a self-rated, single-item measure for evaluating diet quality among individuals and populations. METHODS: A 24-h dietary recall and single-item self-rated diet quality measure were collected for 485 adults. From dietary recalls, Healthy Eating Index-2010 (HEI) scores were computed and compared with self-rated diet quality. Data were collected in 2013 among adult (18 years and older) New York City residents. RESULTS: The study sample was 57% female, 47% white, 56% college educated, and 45% in the highest income tertile. The mean HEI score was 56.5 out of a possible 100. Women averaged higher HEI scores compared to men (58.1 vs 54.3, p = .01). There was a modest yet significant correlation between HEI scores and self-rated diet quality (ρ = 0.29, p < .01). Overall, mean HEI score increased as self-rated diet quality improved (from 48.2 for "poor" to 63.0 for "excellent"). CONCLUSIONS: The single-item measure of self-rated diet quality may provide a simple method of identifying those with the worst diet quality. Further investigation of this measure's validity is needed with alternative measures of dietary intake and with health outcomes.

Using GPS Data to Study Neighborhood Walkability and Physical Activity.

INTRODUCTION: Urban form characteristics intended to support pedestrian activity, collectively referred to as neighborhood walkability, are thought to increase total physical activity. However, little is known about how neighborhood walkability influences utilization of neighborhood space by residents and their overall physical activity. METHODS: Sociodemographic information and data on mobility and physical activity over 1-week periods measured by GPS loggers and accelerometers were collected from 803 residents of New York City between November 2010 and November 2011. Potentially accessible neighborhood areas were defined as land area within a 1-kilometer distance of the subject's home (radial buffer) and within a 1-kilometer journey on the street network from the home (network buffer). To define actual areas utilized by subjects, a minimum convex polygon was plotted around GPS waypoints falling within 1 kilometer of the home. A neighborhood walkability scale was calculated for each neighborhood area. Data were analyzed in 2014. RESULTS: Total residential neighborhood space utilized by subjects was significantly associated with street intersection density and was significantly negatively associated with residential density and subway stop density within 1 kilometer of the home. Walkability scale scores were significantly higher within utilized as compared with non-utilized neighborhood areas. Neighborhood walkability in the utilized neighborhood area was positively associated with total weekly physical activity (32% [95% CI=17%, 49%] more minutes of moderate-equivalent physical activity across the interquartile range of walkability). CONCLUSION: Neighborhood walkability is associated with neighborhood spaces utilized by residents and total weekly physical activity.

Construct validity of a single-item, self-rated question of diet quality.

OBJECTIVE: To provide evidence of the construct validity of a single-item overall diet question with a nomological network of self-rated and biometric measures of dietary intake and outcomes. METHODS: The authors conducted a secondary analysis of survey and biometric data from a cross-sectional sample of urban-dwelling adults. In addition to self-rated diet quality, they examined dietary behaviors, biomarkers of intake, and related outcomes. Self-rated diet quality was treated as a continuous variable to calculate P for trend using regression analysis. RESULTS: Self-rated diet quality was significantly associated with variation in both subjective and objective measures of dietary intake (fruit and vegetable intake, P < .001; sugar-sweetened beverage intake, P < .001; sodium to potassium ratio, P < .001), behavior (frequency of fast-food dining, P < .001), and related outcomes (systolic blood pressure, P = .010; diastolic blood pressure, P < .001; and body mass index, P < .001). CONCLUSIONS AND IMPLICATIONS: Evidence supports the construct validity of a single-item measure of diet quality. This single-item question may be a useful proxy for more burdensome measures of overall diet quality.

Use of sodium information on the nutrition facts label in New York City adults with hypertension.

The Nutrition Facts (NF) label was established to help individuals monitor their nutrient intake and select healthier foods. This tool is particularly useful for individuals for whom dietary improvements are recommended, such as those with hypertension. Study objectives were to examine the independent association between hypertension and frequency of use of the NF label for sodium information and determine whether frequent use in individuals with hypertension was associated with differences in mean sodium intake assessed through 24-hour urine samples. Data came from the New York City Community Health Survey Heart Follow-Up Study, a cross-sectional study conducted in 2010 in a representative sample of New York City adults (n=1,656). Participants were asked questions regarding frequency of checking the NF label and also had 24-hour urine samples collected to assess actual sodium intake. Results indicated that hypertension was associated with frequent use of the NF label for sodium information (adjusted odds ratio 1.71, 95% CI 1.07 to 2.73). In individuals with hypertension, sodium intake did not differ between frequent vs nonfrequent use of the NF label for sodium information (3,084 mg/day vs 3,059 mg/day; P=0.92). Although individuals with hypertension compared to those with no hypertension had 71% higher odds of frequently using the NF label for sodium information, suggesting they may be interested in decreasing sodium intake, sodium intake did not differ by frequency of NF label use among those with hypertension. Future research should explore strategies to ensure that when nutrition information is used, it is translated into meaningful results, especially in individuals with health concerns such as hypertension.

Case fatality rates based on population estimates of influenza-like illness due to novel H1N1 influenza: New York City, May-June 2009.

BACKGROUND: The public health response to pandemic influenza is contingent on the pandemic strain's severity. In late April 2009, a potentially pandemic novel H1N1 influenza strain (nH1N1) was recognized. New York City (NYC) experienced an intensive initial outbreak that peaked in late May, providing the need and opportunity to rapidly quantify the severity of nH1N1. METHODS AND FINDINGS: Telephone surveys using rapid polling methods of approximately 1,000 households each were conducted May 20-27 and June 15-19, 2009. Respondents were asked about the occurrence of influenza-like illness (ILI, fever with either cough or sore throat) for each household member from May 1-27 (survey 1) or the preceding 30 days (survey 2). For the overlap period, prevalence data were combined by weighting the survey-specific contribution based on a Serfling model using data from the NYC syndromic surveillance system. Total and age-specific prevalence of ILI attributed to nH1N1 were estimated using two approaches to adjust for background ILI: discounting by ILI prevalence in less affected NYC boroughs and by ILI measured in syndromic surveillance data from 2004-2008. Deaths, hospitalizations and intensive care unit (ICU) admissions were determined from enhanced surveillance including nH1N1-specific testing. Combined ILI prevalence for the 50-day period was 15.8% (95% CI:13.2%-19.0%). The two methods of adjustment yielded point estimates of nH1N1-associated ILI of 7.8% and 12.2%. Overall case-fatality (CFR) estimates ranged from 0.054-0.086 per 1000 persons with nH1N1-associated ILI and were highest for persons>or=65 years (0.094-0.147 per 1000) and lowest for those 0-17 (0.008-0.012). Hospitalization rates ranged from 0.84-1.34 and ICU admission rates from 0.21-0.34 per 1000, with little variation in either by age-group. CONCLUSIONS: ILI prevalence can be quickly estimated using rapid telephone surveys, using syndromic surveillance data to determine expected "background" ILI proportion. Risk of severe illness due to nH1N1 was similar to seasonal influenza, enabling NYC to emphasize preventing severe morbidity rather than employing aggressive community mitigation measures.