Abstract:

This study aimed to estimate the population-based Parkinson disease prevalence, and to explore potentially associated factors and conditions. A population-based survey was conducted in Northern Peru. Symptoms compatible with Parkinson’s were defined using a validated Spanish questionnaire (≥ 42 points suggest Parkinson’s). Potential factors (e.g., age, sex, etc.) and clinical conditions (e.g., depressive symptoms, perceived stress, etc.) associated with Parkinson’s were assessed. In total, 1,609 subjects were included, mean age of participants was 48.2 (SD: 10.6), and 810 (50.3%) were women. Parkinson’s prevalence was 1.6% (95%CI: 1.0; 2.4). Those aged ≥ 55 years, and those who reported using wood as fuel for household cooking had a Parkinson’s prevalence from 3.5 to 4 times greater than those who did not. The presence of depressive symptoms, anxiety symptoms, perceived stress, poor sleep quality, and cognitive impairment was more common among those with Parkinson’s, and quality of life in these participants was lower than those without Parkinson’s. In conclusion, 1.6% of the population shows symptoms compatible with Parkinson’s. Age and use of wood for household cooking were factors associated with Parkinson’s. Several mental health conditions and lower quality of life were more frequent among those with Parkinson’s. Appropriate strategies are required to detect, prevent, and manage Parkinson’s cases.

Keywords:
Parkinson Disease; Depression; Anxiety; Cognitive Dysfunction; Quality of Life

Resumen:

Este estudio tuvo como objetivo estimar la prevalencia poblacional de la enfermedad de Parkinson y explorar los factores y condiciones potencialmente asociados. Se realizó una encuesta con base poblacional en el norte del Perú. Los síntomas consistentes con la enfermedad de Parkinson se definieron a partir de un cuestionario validado en español (≥ 42 puntos sugieren enfermedad de Parkinson). Se evaluaron los factores potenciales (edad, sexo, etc.) y el estado clínico (síntomas depresivos, estrés percibido, etc.) asociados con la enfermedad de Parkinson. Participaron 1.609 personas, de edad media de 48,2 (DE: 10,6) y 810 (50,3%) participantes eran del sexo feminino. La prevalencia de la enfermedad fue del 1,6% (IC95%: 1,0; 2,4). Los participantes de edad superior a 55 años y los que usaban leña para cocinar tuvieron una prevalencia de 3,5 a 4 veces mayor de presentar enfermedad de Parkinson en comparación con aquellos que no lo hicieron. La presencia de síntomas depresivos, ansiedad, estrés percibido, mala calidad del sueño y deterioro cognitivo fueron más frecuentes entre aquellos con enfermedad de Parkinson; y la calidad de vida en estos participantes fue menor en comparación con la de las personas sin enfermedad de Parkinson. Se concluye que el 1,6% de esta población presenta síntomas compatibles con la enfermedad de Parkinson. La edad y el uso de leña para cocinar fueron factores asociados a enfermedad de Parkinson. Diversas condiciones de salud mental y menor calidad de vida fueron más frecuentes entre las personas con enfermedad de Parkinson. Se necesitan estrategias específicas para el diagnóstico, prevención y tratamiento de los casos de enfermedad de Parkinson.

Palabras-clave:
Enfermedad de Parkinson; Depresión; Ansiedad; Disfunción Cognitiva; Calidad de Vida

Resumo:

Este estudo teve como objetivo estimar a prevalência populacional da doença de Parkinson e explorar fatores e condições potencialmente associados. Uma pesquisa de base populacional foi realizada no norte do Peru. Os sintomas compatíveis com doença de Parkinson foram definidos por meio de um questionário em espanhol validado (≥ 42 pontos sugerem doença de Parkinson). Foram avaliados fatores potenciais (p.ex.:, idade, sexo etc.) e condições clínicas (p.ex.: sintomas depressivos, estresse percebido etc.) associados à doença de Parkinson. No total, foram incluídos 1.609 sujeitos, a média de idade dos participantes foi de 48,2 (DP: 10,6) e 810 (50,3%) eram mulheres. A prevalência da doença foi de 1,6% (IC95%: 1,0; 2,4). Aqueles com idade ≥ 55 anos e aqueles que relataram usar lenha como combustível para cozinhar em casa tiveram prevalência de doença de Parkinson de 3,5 a 4 vezes maior do que aqueles que não. A presença de sintomas depressivos, sintomas de ansiedade, estresse percebido, má qualidade do sono e comprometimento cognitivo foram os mais comuns entre aqueles com doença de Parkinson, e a qualidade de vida nesses participantes foi menor do que a daqueles sem doença de Parkinson. Em conclusão, 1,6% da população apresenta sintomas compatíveis com doença de Parkinson. A idade e o uso de lenha para cozinhar em casa foram fatores associados à doença de Parkinson. Várias condições de saúde mental e menor qualidade de vida foram mais frequentes entre aqueles com doença de Parkinson. Estratégias apropriadas são necessárias para detectar, prevenir e gerenciar casos de doença de Parkinson.

Palavras-chave:
Doença de Parkinson; Depressão; Ansiedade; Disfunção Cognitiva; Qualidade de Vida

Introduction

Globally, Parkinson disease is one of the most common neurodegenerative conditions, characterized by progressive motor symptoms ¹1. Bloem BR, Okun MS, Klein C. Parkinson's disease. Lancet 2021; 397:2284-303.. According to the Global Burden of Disease Study (GBD), an increase in the number of Parkinson’s cases has been observed worldwide since 1990 ²2. Ou Z, Pan J, Tang S, Duan D, Yu D, Nong H, et al. Global trends in the incidence, prevalence, and years lived with disability of Parkinson's disease in 204 countries/territories from 1990 to 2019. Front Public Health 2021; 9:776847.. In women, the incidence rate has increased from 3.3 at the age of 40-49 years to 103.5 per 100,000 people-year in those ≥ 80 years of age; whereas in men, these estimates were 3.6 and 258.5 per 100,000 person-years, respectively ³3. Hirsch L, Jette N, Frolkis A, Steeves T, Pringsheim T. The incidence of Parkinson's disease: a systematic review and meta-analysis. Neuroepidemiology 2016; 46:292-300.. In Peru, the prevalence of Parkinson’s has been estimated being greater among females (1.8%) than males (0.9%) aged 65 years and over ⁴4. Llibre-Guerra JJ, Prina M, Sosa AL, Acosta D, Jimenez-Velazquez IZ, Guerra M, et al. Prevalence of parkinsonism and Parkinson disease in urban and rural populations from Latin America: a community based study. Lancet Reg Health Am 2022; 7:100136..

As the aging process affects the general population, it is mandatory to determine the prevalence, as well as the factors and conditions associated with certain neurodegenerative conditions, especially in resource-constrained settings. Thus, such information can serve to inform policies, interventions, and priorities, as well as patient screening. Estimating common epidemiological indicators (e.g., prevalence) of these conditions is one of the major issues due to the difficulty of performing the diagnosis, as a structured interview is usually required, as well as physical and neurological examinations performed by specialists. However, several tools and scales can aid estimate the prevalence of motor symptoms of Parkinson’s and, thus, provide preliminary evidence on the prevalence of Parkinson’s in the general population ⁵5. Duarte J, Clavería LE, de Pedro-Cuesta J, Sempere AP, Coria F, Calne DB. Screening Parkinson's disease: a validated questionnaire of high specificity and sensitivity. Mov Disord 1995; 10:643-9.^,66. Richards M, Marder K, Cote L, Mayeux R. Interrater reliability of the Unified Parkinson's Disease Rating Scale motor examination. Mov Disord 1994; 9:89-91.^,77. van Wamelen DJ, Martinez-Martin P, Weintraub D, Schrag A, Antonini A, Falup-Pecurariu C, et al. The Non-Motor Symptoms Scale in Parkinson's disease: validation and use. Acta Neurol Scand 2021; 143:3-12..

Age and schooling level have been associated with the presence of Parkinson’s ⁸8. Orozco JL, Valderrama-Chaparro JA, Pinilla-Monsalve GD, Molina-Echeverry MI, Pérez Castaño AM, Ariza-Araújo Y, et al. Parkinson's disease prevalence, age distribution and staging in Colombia. Neurol Int 2020; 12:8401.^,99. Prajjwal P, Flores Sanga HS, Acharya K, Tango T, John J, Rodriguez RSC, et al. Parkinson's disease updates: addressing the pathophysiology, risk factors, genetics, diagnosis, along with the medical and surgical treatment. Ann Med Surg (Lond) 2023; 85:4887-902.^,1010. Simon DK, Tanner CM, Brundin P. Parkinson disease epidemiology, pathology, genetics, and pathophysiology. Clin Geriatr Med 2020; 36:1-12.; nevertheless, few studies have evaluated the associated factors in low-income countries, which present different sociodemographic and epidemiological profiles, as well as determinants of access to health. Recently, a report using information from the 10/66 Study⁴4. Llibre-Guerra JJ, Prina M, Sosa AL, Acosta D, Jimenez-Velazquez IZ, Guerra M, et al. Prevalence of parkinsonism and Parkinson disease in urban and rural populations from Latin America: a community based study. Lancet Reg Health Am 2022; 7:100136., conducted with people aged 65 years and older from urban and rural areas, reported that Parkinson’s was more frequent at older ages and in those with a lower schooling level. On the other hand, other studies have focused on conditions that usually occur in those with Parkinson’s, such as mental health conditions, including depression ¹¹11. Cong S, Xiang C, Zhang S, Zhang T, Wang H, Cong S. Prevalence and clinical aspects of depression in Parkinson's disease: a systematic review and meta-analysis of 129 studies. Neurosci Biobehav Rev 2022; 141:104749. and cognitive impairment (dementia) ⁴4. Llibre-Guerra JJ, Prina M, Sosa AL, Acosta D, Jimenez-Velazquez IZ, Guerra M, et al. Prevalence of parkinsonism and Parkinson disease in urban and rural populations from Latin America: a community based study. Lancet Reg Health Am 2022; 7:100136.. Evaluating different aspects of mental health and quality of life in these patients becomes a priority to understand the multimorbidity profile that they have. Therefore, people with Parkinson’s can be approached holistically, considering their entire health profile, rather than only Parkinson’s.

As a result, the main aim of this study was twofold: (i) to determine the prevalence of symptoms compatible with Parkinson’s at the population level, and (ii) to explore the potential factors and conditions associated with these symptoms, reanalyzing the data from a population study carried out in the north of Peru.

Methods

Design and study location

This is a secondary data analysis using a study to evaluate screening methods for type 2 diabetes mellitus at the population level ¹²12. Bernabe-Ortiz A, Perel P, Miranda JJ, Smeeth L. Diagnostic accuracy of the Finnish Diabetes Risk Score (FINDRISC) for undiagnosed T2DM in Peruvian population. Prim Care Diabetes 2018; 12:517-25.. Fieldwork activities were conducted in the periurban area of Tumbes, in Northern Peru, during December 2016 and November 2017.

Study population and sampling

Selection criteria of the original study included men and women, aged 30 to 69 years, habitual residents living ≥ 6 months in the study area, and capable of signing an informed consent form to participate. Pregnant patients at the moment of the study, as well as those bedridden or with physical disabilities precluding anthropometric measurements, were excluded. For this analysis, only those with incomplete information in the Parkinson’s evaluation were not included.

Participants were selected from the general population, regardless of any previous condition before selection. Sampling was conducted using a sex-stratified random approach, and study participants were selected using the most current census of the area (2014). Only one participant per household was enrolled in the study to avoid clustering of common risk factors.

Since this is a secondary analysis, with 1,600 participants, we will be able to detect a Parkinson’s prevalence of 1.6% with a precision of 0.7% and a 95% confidence level.

Study variables

The variable of interest was the presence of symptoms compatible with Parkinson’s, obtained using the 9-item screening questionnaire developed by Tanner symptom questionnaire ¹³13. Tanner CM, Gilley DW, Goetz CG. A brief screening questionnaire for Parkinsonism. Ann Neurol 1990; 28:267-8., translated and adapted by Duarte et al. in Spain ⁵5. Duarte J, Clavería LE, de Pedro-Cuesta J, Sempere AP, Coria F, Calne DB. Screening Parkinson's disease: a validated questionnaire of high specificity and sensitivity. Mov Disord 1995; 10:643-9.. The instrument comprises nine questions that can be administered by a trained interviewer or physician or self-administered. In answering this instrument, participants have two potential responses (yes/no), which are weighted considering the common deficits associated with Parkinson’s to improve the specificity of the instrument. Thus, the score can range from 0 to 67, and it is considered positive (that is, it suggests Parkinson’s) in those with ≥ 42 points. With this cut-off point, the sensitivity and specificity of the instrument has been described as close to 100% ⁵5. Duarte J, Clavería LE, de Pedro-Cuesta J, Sempere AP, Coria F, Calne DB. Screening Parkinson's disease: a validated questionnaire of high specificity and sensitivity. Mov Disord 1995; 10:643-9..

Potential factors associated with Parkinson’s and reported in literature were included: sex (man vs. women), age group (< 40, 40-54, and 55+ years), schooling level (primary [< 7 years], secondary [7-11 years], and tertiary [12+ years]), socioeconomic status (based on household possessions and categorized into tertiles), use of firewood/wood as fuel for household cooking (rather than propane gas, yes/no), history of tobacco use (never/ever in life), alcohol consumption (never/ever in life), physical activity levels (based on the International Physical Activity Questionnaire - Short Form [IPAQ-SF], and classified as low/moderate or high), body mass index (normal, overweight, and obesity, defined based on international standards), hypertension (defined based on blood pressure measurements [systolic ≥ 140mmHg or diastolic ≥ 90mmHg] or previous self-reported medical diagnosis) ¹⁴14. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo Jr. JL, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003; 289:2560-72., and type 2 diabetes mellitus (defined according to the oral glucose tolerance test [fasting glucose ≥ 126mg/dL or postprandial glucose ≥ 200mg/dL] or previous medical diagnosis) ¹⁵15. ElSayed NA, Aleppo G, Aroda VR, Bannuru RR, Brown FM, Bruemmer D, et al. 2. Classification and diagnosis of diabetes: standards of care in diabetes-2023. Diabetes Care 2023; 46 Suppl 1:S19-40..

Mental health conditions were evaluated as potential factors associated with Parkinson’s. The presence of depressive symptoms was evaluated using the Patient Health Questionnaire-9 (PHQ-9), a 9-item instrument with four response options ranging from “not at all” to “nearly every day”; a score ≥ 5 was defined as a cut-off point, compatible with the presence of mild depressive symptoms ¹⁶16. Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med 2001; 16:606-13.^,1717. Villarreal-Zegarra D, Copez-Lonzoy A, Bernabé-Ortiz A, Melendez-Torres GJ, Bazo-Alvarez JC. Valid group comparisons can be made with the Patient Health Questionnaire (PHQ-9): a measurement invariance study across groups by demographic characteristics. PLoS One 2019; 14:e0221717.. The presence of anxiety symptoms was assessed using the Goldberg Anxiety Scale (GAS), a 9-item instrument that allows dichotomous answers (yes/no); a score ≥ 4 was defined as a cut-off point for the presence of symptoms compatible with anxiety ¹⁸18. Reivan-Ortiz G, Pineda-Garcia G, León-Parias BD. Psychometric properties of the Goldberg Anxiety and Depression Scale (GADS) in Ecuadorian population. Int J Psychol Res (Medellin) 2019; 12:41-8.. Perceived stress was assessed using the Perceived Stress Scale (PSS), a 14-item tool to rate feelings and thoughts about life events using a 5-point Likert type scale, ranging from “never” to “very often” ¹⁹19. Cohen S, Kamarck T, Mermelstein R. A global measure of perceived stress. J Health Soc Behav 1983; 24:385-96.. For this analysis, the level of perceived stress was divided into tertiles (low, moderate, and high) and compared considering the high-level category versus the grouped low- and moderate-level categories. Sleep quality was assessed using the Pittsburgh Sleep Quality Index²⁰20. Buysse DJ, Reynolds 3rd CF, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res 1989; 28:193-213., a 21-question instrument (subjective sleep quality, duration, sleep disturbances, latency, use of sleep medication, efficiency, and nocturnal dysfunction). The global score ranges from 0 to 21 points, in which > 5 points is considered a cut-off point for poor sleep quality. Cognitive impairment was assessed using the Leganés Cognitive Test (LST) ²¹21. De Yébenes MJ, Otero A, Zunzunegui MV, Rodríguez-Laso A, Sánchez-Sánchez F, Del Ser T. Validation of a short cognitive tool for the screening of dementia in elderly people with low educational level. Int J Geriatr Psychiatry 2003; 18:925-36. with a cut-off point of < 26. The test consists of 32 items that mainly evaluate memory, orientation, and attention. Finally, quality of life was assessed using the EuroQoL-5 Dimension (EQ-5D) ²²22. Janssen MF, Pickard AS, Golicki D, Gudex C, Niewada M, Scalone L, et al. Measurement properties of the EQ-5D-5L compared to the EQ-5D-3L across eight patient groups: a multi-country study. Qual Life Res 2013; 22:1717-27., a questionnaire that includes a visual analogue scale to determine perceived quality of life by asking participants to classify their current state of well-being from zero, the worst health imaginable, to 100, the best health imaginable.

Procedures

Data collection was conducted using tablet devices and the Open Data Kit (https://opendatakit.org/software/), an open-source mobile data collection platform that allows users to complete and save offline forms and then upload data to a server when Internet connection is available.

Fieldworkers were trained to administer the questionnaire and perform anthropometric measurements. Weight and height, to estimate body mass index (BMI), were obtained using standard techniques. Blood pressure was measured in triplicate using an automatic monitor (HEM-780, OMRON; https://www.omron.com/global/en/), collected after five minutes of resting with at least one minute between measurements. The average of the second and third measurements were used for analysis ¹⁴14. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo Jr. JL, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003; 289:2560-72..

The glucose tolerance test was performed using international standards, with an 75g anhydrous glucose load and blood samples taken after 8-12 hours of fasting, and 2 hours postprandial ¹⁵15. ElSayed NA, Aleppo G, Aroda VR, Bannuru RR, Brown FM, Bruemmer D, et al. 2. Classification and diagnosis of diabetes: standards of care in diabetes-2023. Diabetes Care 2023; 46 Suppl 1:S19-40.. Forms and questionnaires, as well as body measurements, were administered and performed between sample collection for glucose tolerance.

Statistical analysis

Analyses were performed using the Stata statistical software, version 16 (https://www.stata.com). Data were described using means and standard deviations (SD) for numerical variables, and absolute and relative frequencies for categorical variables. Cronbach’s alpha was used to evaluate the reliability of the instrument used to evaluate Parkinson’s, using 0.70 as a cut-off point to be considered acceptable ²³23. Schrepp M. On the usage of Cronbach's alpha to measure reliability of UX scales. J Usability Stud 2020; 15:247-58.. The prevalence and 95% confidence intervals (95%CI) of variables of interest were reported and, considering the limited number of events, differences in the distribution of Parkinson’s frequency according to the covariates were estimated using the Fisher’s exact test.

To explore the factors associated with Parkinson’s, Poisson regression models with robust variance were used. Given the exploratory nature of this analysis, in which Parkinson’s was the dependent variable, the multivariable model included all the studied variables according to the literature and that were available in the database, reporting prevalence ratios (PR) and 95%CIs.

Furthermore, to evaluate the conditions associated with Parkinson’s (considered in this case as an exposure variable), Poisson regression models were also built, both crude and adjusted but, in this case, the multivariable models were adjusted only for the most relevant confounding factors, that is, age, sex, schooling level, socioeconomic level, and PRs and 95%CIs were reported.

Regarding quality of life, given that it is a numerical variable, linear regression models with robust variance were used and coefficients (β) and 95%CIs were estimated. In all cases, a value of p < 0.05 was considered statistically significant.

Ethical aspects

The study protocol and informed consent forms were approved by the Research Ethics Committees of the Cayetano Heredia Peruvian University (Universidad Peruana Cayetano Heredia, Peru) and the London School of Hygiene and Tropical Medicine (United Kingdom). Written informed consent was applied before commencing study activities. The database was de-identified to guarantee the anonymity of the participants.

Results

Characteristics of the study population

A total of 2,114 subjects were invited to the study, and of them, 486 (22.9%) refused to participate, whereas 16 (0.8%) women were pregnant at the time of the study and were excluded. Of the 1,612 (76.3%) subjects enrolled, three did not complete all phases of the study and, thus, 1,609 participants were analyzed in the present work. Mean age of participants was 48.2 years (SD: 10.6), 810 (50.3%) were women, and 519 (32.3%) had at least primary education.

Prevalence of Parkinson disease and associated factors

The reliability of the 9-item questionnaire used to assess Parkinson’s was in an acceptable range (Cronbach’s α = 0.76). In total, 26 (1.6%; 95%CI: 1.0; 2.4) subjects presented symptoms and scores compatible with Parkinson’s. This condition was more frequent among females, those 55+ years old, with a lower schooling level, those who reported using wood as fuel for household cooking, and in those with obesity, hypertension, and type 2 diabetes mellitus (Table 1).

In the multivariable model, those aged 55+ years (PR = 4.05; 95%CI: 1.01; 16.34) and those who reported using wood as fuel for household cooking (PR = 3.45; 95%CI: 1.25; 9.48) were most likely to have symptoms compatible with Parkinson’s (Table 2).

Conditions associated with Parkinson disease

Mental health and clinical conditions evaluated were significantly associated with the presence of Parkinson’s (Table 3). In a multivariable model of patients with Parkinson’s, adjusted for age, sex, schooling level, and socioeconomic level, the presence of Parkinson’s was associated with significant increases in various mental health conditions compared to those without Parkinson’s. Specifically, the presence of Parkinson’s was linked to a 181% increase (95%CI: 115; 269) in the prevalence of depressive symptoms, a 100% increase (95%CI: 71; 133) in anxiety symptoms, a 140% increase (95%CI: 93; 199) in high perceived stress, a 140% increase (95%CI: 66; 246) in poor sleep quality, and a 93% (95%CI: 3; 262) increase in cognitive impairment. Finally, participants with symptoms compatible with Parkinson’s had a quality of life 15.6 (95%CI: 8.0; 23.3) points lower than those without those symptoms.

Discussion

Main findings

This study shows that 1.6% of the general population in a periurban site in Northern Peru aged from 30 to 69 years had symptoms compatible with Parkinson’s, being higher in those ≥ 55 years of age. Moreover, the self-reported use of wood/firewood as fuel for household cooking was a factor significantly associated with Parkinson’s. Finally, several mental health conditions were more frequent among those with Parkinson’s, including symptoms of depression, anxiety, perceived stress, poor quality of sleep, cognitive impairment, and lower quality of life, compared to those without Parkinson’s.

Comparison with previous studies

A recent systematic review about Parkinson’s in Latin America reported 0.47% prevalence using information from 17 studies ²⁴24. Kim DJ, Isidro-Pérez AL, Doering M, Llibre-Rodriguez JJ, Acosta I, Rodriguez Salgado AM, et al. Prevalence and incidence of Parkinson's disease in Latin America: a meta-analysis. Mov Disord 2024; 39:105-18.; however, estimates differed by data source and age. According to a global study, more than 8 million individuals had Parkinson’s worldwide in 2019, with a relative percentage change greater than 150% compared to 1990 ²2. Ou Z, Pan J, Tang S, Duan D, Yu D, Nong H, et al. Global trends in the incidence, prevalence, and years lived with disability of Parkinson's disease in 204 countries/territories from 1990 to 2019. Front Public Health 2021; 9:776847.. In the same study, this value for Andean Latin America, where Peru is located, has been estimated at 54,000 subjects with Parkinson’s with an increase of 107% in the same period. The 10/66 Study, which enrolled subjects ≥ 65 years of age, reported that Parkinson’s prevalence in the urban area of Lima was 7.9%, whereas in the rural area of Cañete (south of Lima) it was 6.6% ⁴4. Llibre-Guerra JJ, Prina M, Sosa AL, Acosta D, Jimenez-Velazquez IZ, Guerra M, et al. Prevalence of parkinsonism and Parkinson disease in urban and rural populations from Latin America: a community based study. Lancet Reg Health Am 2022; 7:100136.. Although our results show lower estimates, the results were obtained via neurological tests and evaluations conducted by specialists in the 10/66 Study, thus they were able to capture more cases compared to our study. Moreover, since age groups were different, our estimates showed lower results than those reported in the 10/66 Study.

On the other hand, in other similar contexts such as Colombia, the age-adjusted prevalence of Parkinson’s was 0.3% in individuals aged 60-69 years, 1.1% in those aged 70-79 years, and 1.8% in those aged 80-89 years ⁸8. Orozco JL, Valderrama-Chaparro JA, Pinilla-Monsalve GD, Molina-Echeverry MI, Pérez Castaño AM, Ariza-Araújo Y, et al. Parkinson's disease prevalence, age distribution and staging in Colombia. Neurol Int 2020; 12:8401.. Nevertheless, in this last study, Parkinson’s was defined based on a clinical diagnosis algorithm and pharmacological prescription of each subject. Thus, our results, based on a motor symptoms questionnaire for Parkinson’s, are within the expected values for this condition according to other studies in similar contexts.

Regarding the associated factors, as in other studies, older age was associated with a higher prevalence of Parkinson’s ⁸8. Orozco JL, Valderrama-Chaparro JA, Pinilla-Monsalve GD, Molina-Echeverry MI, Pérez Castaño AM, Ariza-Araújo Y, et al. Parkinson's disease prevalence, age distribution and staging in Colombia. Neurol Int 2020; 12:8401.^,2424. Kim DJ, Isidro-Pérez AL, Doering M, Llibre-Rodriguez JJ, Acosta I, Rodriguez Salgado AM, et al. Prevalence and incidence of Parkinson's disease in Latin America: a meta-analysis. Mov Disord 2024; 39:105-18.. Moreover, the self-reported use of firewood/wood as fuel for household cooking was strongly associated with the presence of Parkinson’s, even after controlling for different confounders. Tumbes, the area of study, is an arid and subtropical region located in Northern Peru, close to the border with Ecuador. Use of wood for household cooking is important, especially in rural and semiurban areas, where the study was conducted, but this activity is usually carried out outdoors, as weather temperature averages from 27ºC to 35ºC ²⁵25. Instituto Nacional de Estadística e Informática. Perú: temperatura promedio, máxima y mínima, según departamento. Lima: Instituto Nacional de Estadística e Informática; 2023.. According to the literature, certain pollutants, such as tobacco or exposure to pesticides, are consistently associated with higher prevalence of Parkinson’s, as well as environmental pollution ²⁶26. Murata H, Barnhill LM, Bronstein JM. Air pollution and the risk of Parkinson's disease: a review. Mov Disord 2022; 37:894-904.. Long-term exposure to some metals, such as copper, manganese, mercury, zinc, and lead, have also been associated with higher Parkinson’s risk ²⁷27. Gorell JM, Johnson CC, Rybicki BA, Peterson EL, Kortsha GX, Brown GG, et al. Occupational exposures to metals as risk factors for Parkinson's disease. Neurology 1997; 48:650-8.. Thus, although wood/firewood smoke could be one of these pollutants, other related chemicals, such as the type of wood used or contamination with pesticides, could be options to consider. For example, a study conducted in Louisiana, in the United States, using information from hospital primary discharge, reported that commercial forests, woodlands, and pastures - thus, some pastoral pesticides - may be associated with Parkinson’s ²⁸28. Hugh-Jones ME, Peele RH, Wilson VL. Parkinson's disease in Louisiana, 1999-2012: based on hospital primary discharge diagnoses, incidence, and risk in relation to local agricultural crops, pesticides, and aquifer recharge. Int J Environ Res Public Health 2020; 17:1584.. Agriculture and pesticide use (i.e., paraquat and methomyl 90SP) are common in Tumbes, and metal contamination of water with cadmium and arsenic has been described as well. Thus, this is a topic that requires further study using longitudinal studies.

Finally, several conditions, especially related to mental health and quality of life, were associated with Parkinson’s. In all cases, the presence of Parkinson’s at least doubles the prevalence of any mental health indicator, as the literature demonstrates in the case of depression ¹¹11. Cong S, Xiang C, Zhang S, Zhang T, Wang H, Cong S. Prevalence and clinical aspects of depression in Parkinson's disease: a systematic review and meta-analysis of 129 studies. Neurosci Biobehav Rev 2022; 141:104749. and anxiety ²⁹29. Broen MP, Narayen NE, Kuijf ML, Dissanayaka NN, Leentjens AF. Prevalence of anxiety in Parkinson's disease: a systematic review and meta-analysis. Mov Disord 2016; 31:1125-33.. In the case of cognitive impairment, even the medication used, including levodopa, has been associated with cognition, both in deleterious ways and with beneficial effects, depending on the person’s susceptibility ³⁰30. Aarsland D, Batzu L, Halliday GM, Geurtsen GJ, Ballard C, Chaudhuri KR, et al. Parkinson disease-associated cognitive impairment. Nat Rev Dis Primers 2021; 7:47.. Finally, regarding quality of life, a systematic review shows that people with Parkinson’s have lower quality of life compared to healthy controls in almost all domains, especially in physical and mental function ³¹31. Zhao N, Yang Y, Zhang L, Zhang Q, Balbuena L, Ungvari GS, et al. Quality of life in Parkinson's disease: a systematic review and meta-analysis of comparative studies. CNS Neurosci Ther 2021; 27:270-9., probably because people with Parkinson’s cannot, or need help, to perform basic daily tasks.

Public health relevance

This study highlights several aspects of interest. First, the need for appropriate tools to detect and screen Parkinson’s at the population level. This is important since the literature has been demonstrating an aging process in the general population, which leads to the increase in degenerative diseases ²⁴24. Kim DJ, Isidro-Pérez AL, Doering M, Llibre-Rodriguez JJ, Acosta I, Rodriguez Salgado AM, et al. Prevalence and incidence of Parkinson's disease in Latin America: a meta-analysis. Mov Disord 2024; 39:105-18.^,3232. GBD 2016 Parkinson's Disease Collaborators. Global, regional, and national burden of Parkinson's disease, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet Neurol 2018; 17:939-53., including neurological conditions. If a single instrument appears to be insufficient to “diagnose” Parkinson’s or other neurodegenerative diseases, then an algorithm that combines several instruments and other variables should be designed. Second, determining, in greater detail, the factors that may favor the increase of Parkinson’s cases. In addition to age, the involvement of contaminants, such as wood for household cooking, must be explored longitudinally to reduce the onset of new cases. There is a possibility that contamination of firewood may be playing a role in the presence of Parkinson’s cases. Third, cases with Parkinson’s should be evaluated and treated appropriately for various mental health conditions. Finally, interventions are warranted to improve the quality of life of those suffering from Parkinson’s. This includes not only appropriate medication, but also comprehensive case management, such as management of sleep quality and stress, both for the patient and their close network, including family and caregiver. Similarly, the health and well-being of the close family of patients with Parkinson’s, particularly those who play the role of caregivers, must be studied and cared for.

Strengths and limitations

This work benefits from using data from a population-based study in a specific area of Peru. We also highlight the use of a tool validated in Spanish to determine the outcome of interest. However, this work also shows limitations. First, due to the cross-sectional nature of the study, we cannot assess causality but only association. Although reverse causality and temporality could be concerns, it is unlikely that these exist in this work since several of the potential factors evaluated occurred for a long time prior to the development of Parkinson’s. For instance, household cooking with wood is probably the fuel they have used for many years and not recently adopted. Second, the employed questionnaire is based on the detection of motor symptoms of Parkinson’s (i.e., parkinsonism), which could underestimate the real prevalence of the disease since there are non-motor symptoms that can be highly frequent (about 90% of cases with Parkinson’s present non-motor symptoms) ³³33. Fernandes M, Pierantozzi M, Stefani A, Cattaneo C, Bonizzoni EA, Cerroni R, et al. Frequency of non-motor symptoms in Parkinson's patients with motor fluctuations. Front Neurol 2021; 12:678373.. On the other hand, the instrument used could not capture all cases of Parkinson’s due to the presence of diseases with similar symptoms. Moreover, this tool was designed for clinical settings and not for community use. Despite of that, the scale used has shown good diagnostic performance ⁵5. Duarte J, Clavería LE, de Pedro-Cuesta J, Sempere AP, Coria F, Calne DB. Screening Parkinson's disease: a validated questionnaire of high specificity and sensitivity. Mov Disord 1995; 10:643-9.. Third, there could also be recall bias for some of the questions evaluated, especially those related to behaviors or lifestyles. In addition, pesticide use and other environmental factors associated with Parkinson’s were not evaluated in the original study, thus were not included in this manuscript. Fourth, the limited number of Parkinson’s cases detected in the study could hinder the precision of our estimates. However, our results corroborate previous studies. Finally, there may be selection bias since the chosen study area presents a higher prevalence of certain risk factors (type 2 diabetes mellitus, obesity, and hypertension), which could affect the generalizability of the results.

Conclusions

We found that 1.6% of the general population aged from 30 to 69 years presented symptoms compatible with Parkinson’s. In addition to age, self-reported use of wood/firewood for household cooking was a factor strongly associated with Parkinson’s. Several mental health conditions and lower quality of life were more frequent in those with Parkinson’s when compared to those without Parkinson’s. Appropriate strategies are required for the detection and management of Parkinson’s cases.

References

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